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PROCESS

20230357110 · 2023-11-09

    Inventors

    Cpc classification

    International classification

    Abstract

    The present invention is directed to a process for hydrogenation of an ester-containing substrate, comprising treating an ester-containing substrate with a base and a transition metal catalyst in the presence of molecular hydrogen, wherein the base is present in at least 30 mol % based upon the total amount of ester-containing substrate and wherein the substrate/catalyst loading is greater than or equal to 10,000/1.

    Claims

    1-28. (canceled)

    29. A process for hydrogenation of an ester-containing substrate, comprising treating an ester-containing substrate with a base and a transition metal catalyst in the presence of molecular hydrogen, wherein the base is present in at least 30 mol % based upon the total amount of ester-containing substrate and wherein the substrate/catalyst loading is greater than or equal to 10,000/1.

    30. The process as claimed in claim 29, wherein the base is present in at least 35 mol % based upon the total amount of ester-containing substrate.

    31. The process as claimed in claim 29, wherein the base is present in at least 40 mol % based upon the total amount of ester-containing substrate.

    32. The process as claimed in claim 29, wherein the base is present in at least 45 mol % based upon the total amount of ester-containing substrate.

    33. The process as claimed in claim 29, wherein the base is present in at least 50 mol % based upon the total amount of ester-containing substrate.

    34. The process as claimed in claim 29, wherein the base is a metal alkoxide.

    35. The process as claimed in claim 29, wherein the base is an alkali metal alkoxide.

    36. The process as claimed in claim 29, wherein the base is an alkali metal ethoxide selected from lithium ethoxide, sodium ethoxide or potassium ethoxide.

    37. The process as claimed in claim 29, wherein the process is carried out in the absence of solvent.

    38. The process as claimed in claim 29, wherein the process is carried out in the presence of at least one solvent.

    39. The process as claimed in claim 38, wherein the at least one solvent is selected from an alcohol, toluene, THF and Me-THF.

    40. The process as claimed in claim 38, wherein said at least one solvent is present in an amount of 10 to 100 vol % based upon the total volume of ester-containing substrate.

    41. The process as claimed in claim 29, wherein the process is carried out in the presence of a first solvent and a second solvent.

    42. The process as claimed in claim 41, wherein said first solvent is toluene or THF and said second solvent is an alcohol.

    43. The process as claimed in claim 41, wherein said first solvent is present in an amount of 10 to 100 vol % based upon the total volume of ester-containing substrate.

    44. The process as claimed in claim 41, wherein said second solvent is present in an amount of 1 to 15 vol % based upon the total volume of the ester-containing substrate.

    45. The process as claimed in claim 29, wherein the temperature is in the range 20 to 150° C.

    46. The process as claimed in claim 29, wherein the pressure is in the range 5 to 100 bar.

    47. The process as claimed in claim 29, wherein the substrate/catalyst loading is greater than or equal to 20,000/1.

    48. The process as claimed in claim 29, wherein the substrate/catalyst loading is greater than or equal to 30,000/1.

    49. The process as claimed in claim 29, wherein the substrate/catalyst loading is greater than or equal to 50,000/1.

    50. The process as claimed in claim 29, wherein the substrate/catalyst loading is greater than or equal to 100,000/1.

    51. The process as claimed in claim 29, wherein the transition metal catalyst comprises a tridentate ligand.

    52. The process as claimed in claim 51, wherein the transition metal catalyst comprises a tridentate ligand having a Formula (I) ##STR00020## wherein: X is selected from —SR.sup.a, —OR.sup.a, —CR.sup.a, —NR.sup.aR.sup.b, —PR.sup.aR.sup.b, —P(═O)R.sup.aR.sup.b, —OPR.sup.aR.sup.b, and —NHPR.sup.aR.sup.b; R.sup.1 and R.sup.x are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl, or R.sup.1 and one of R.sup.3a and R.sup.3b or R.sup.x and one of R.sup.3a and R.sup.3b together with the atoms to which they are bound, form a ring; or X is a heteroatom and when taken together with R.sup.1 it forms an optionally substituted heterocycle when R.sup.X is absent; Y is selected from —SR.sup.a, —OR.sup.a, —CR.sup.a, —NR.sup.aR.sup.b, —PR.sup.aR.sup.b, —P(═O)R.sup.aR.sup.b, —OPR.sup.aR.sup.b, and —NHPR.sup.aR.sup.b; R.sup.2 and R.sup.y are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl, or R.sup.2 and one of R.sup.4a and R.sup.4b or R.sup.y and one of R.sup.4a and R.sup.4b together with the atoms to which they are bound, form a ring; or Y is a heteroatom and when taken together with R.sup.2 it forms an optionally substituted heterocycle when R.sup.Y is absent; R.sup.3a, R.sup.3b, R.sup.4a and R.sup.4b are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl, or R.sup.3a and one of R.sup.4a and R.sup.4b or R.sup.3b and one of R.sup.4a and R.sup.4b, together with the atoms to which they are bound, form a heterocycle; R.sup.5 is selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; each m and n is independently 1 or 2; and R.sup.a and R.sup.b, if present, are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; or when X and/or Y is —NR.sup.aR.sup.b, —PR.sup.aR.sup.b, —OPR.sup.aR.sup.b, or —NHPR.sup.aR.sup.b, R.sup.a and R.sup.b together with the heteroatom to which they are attached form a heterocycle.

    53. The process as claimed in claim 29, wherein the transition metal catalyst has a Formula (II) or Formula (III)
    [M(L.sup.1)(L.sup.2).sub.d]  (II)
    [M(L.sup.1)(L.sup.2).sub.d]W  (III) wherein: M is a transition metal; L.sup.1 is a tridentate ligand wherein the substrate/catalyst loading is greater than or equal to 20,000/1; L.sup.2 are ligands which may be the same or different; d is 1, 2 or 3; and W is a non-coordinated anionic ligand.

    54. The process as claimed in claim 53, wherein M is a transition metal selected from Ru and Os, preferably Ru.

    55. The process as claimed in claim 53, wherein each L.sup.2 is independently selected from —H, —CO, —CN, —P(R′).sub.3, —As(R′).sub.3, —CR′, —OR′, —O(C═O)R′, —NR′.sub.2, halogen (e.g. —Cl, —Br, —I), and solvent wherein each R′ is independently selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl.

    56. The process as claimed in claim 29, wherein the transition metal catalyst is ##STR00021##

    57. The process as claimed in claim 29, wherein the ester-containing substrate is of Formula (X) ##STR00022## wherein: R.sup.6 and R.sup.7 are independently organic groups having 1-70 carbon atoms; or R.sup.6/R.sup.7 forms a ring structure with the atoms to which they are attached.

    58. The process as claimed in claim 29, wherein the ester-containing substrate is a methyl ester or an ethyl ester.

    59. The process as claimed in claim 29, which is a batch process, preferably a batch process wherein any excess base is recycled or reused.

    60. The process as claimed in claim 29, which is a batch process wherein any excess base is recycled or reused.

    61. The process as claimed in claim 29, which is a flow process, preferably a flow process wherein any excess base is recycled or reused.

    62. The process as claimed in claim 29, which is a flow process wherein any excess base is recycled or reused.

    Description

    DETAILED DESCRIPTION

    [0037] Preferred and/or optional features of the invention will now be set out. Any aspect of the invention may be combined with any other aspect of the invention, unless the context demands otherwise. Any of the preferred or optional features of any aspect of the invention may be combined, singly or in combination, with any aspect of the invention, unless the context demands otherwise.

    [0038] The present invention provides a process for hydrogenation of an ester-containing substrate, comprising treating an ester-containing substrate with a base and a transition metal catalyst in the presence of molecular hydrogen, wherein the base is present in at least 30 mol % based upon the total amount of ester-containing substrate and wherein the substrate/catalyst loading is greater than or equal to 10,000/1.

    [0039] In preferred processes of the present invention, the base is present in at least 35 mol % based upon the total amount of ester-containing substrate, preferably in at least 40 mol % based upon the total amount of ester-containing substrate, more preferably in at least 45 mol % based upon the total amount of ester-containing substrate, and even more preferably in at least 50 mol % based upon the total amount of ester-containing substrate. Without wishing to be bound by theory, it is thought that the use of high amounts of base in the processes of the present invention allows for the use of lower catalyst loadings compared to known processes. In some cases, extremely low catalyst loadings have been achieved, e.g. S/C=greater than or equal to 100,000/1.

    [0040] In preferred processes of the present invention, the base is present in less than or equal to 200 mol % based upon the total amount of ester-containing substrate, more preferably in less than or equal to 125 mol % based upon the total amount of ester-containing substrate.

    [0041] In preferred processes of the present invention, the base is present in a range of 30 to 70 mol % based upon the total amount of ester-containing substrate, more preferably in a range of 30 to 60 mol % based upon the total amount of ester-containing substrate, even more preferably in a range of 30 to 50 mol % based upon the total amount of ester-containing substrate.

    [0042] In preferred processes of the present invention, the base is a metal alkoxide. The metal alkoxide is preferably a metal methoxide, a metal ethoxide, a metal iso-propoxide, or a metal tert-butoxide. Preferred metal alkoxides include lithium ethoxide, sodium ethoxide, or potassium ethoxide.

    [0043] In preferred processes of the present invention, the base is an alkali metal alkoxide. The alkali metal alkoxide is preferably an alkali metal methoxide, an alkali metal ethoxide, an alkali metal iso-propoxide, or an alkali metal tert-butoxide. The alkali metal alkoxide is more preferably an alkali metal methoxide or an alkali metal ethoxide.

    [0044] In particularly preferred processes of the present invention, the base is an alkali metal ethoxide. The alkali metal ethoxide is preferably lithium ethoxide, sodium ethoxide or potassium ethoxide, more preferably sodium ethoxide.

    [0045] In preferred processes of the present invention, the base is in solid form.

    [0046] In preferred processes of the present invention, the base is supported. More preferably, the base is supported on a resin.

    [0047] In preferred processes of the present invention, the process is carried out in the absence of solvent. This has the advantage of making the process both easier and less expensive to perform.

    [0048] In alternative preferred processes of the present invention, the process is carried out under neat conditions.

    [0049] In alternative preferred processes of the present invention, the process is carried out in the presence of at least one solvent.

    [0050] Preferably, the at least one solvent is selected from an alcohol, toluene, THF and Me-THF. More preferably, the at least one solvent is selected from methanol, ethanol, toluene, THF and Me-THF. Most preferably, the at least one solvent is selected from methanol, ethanol, and toluene.

    [0051] In preferred processes of the present invention, the at least one solvent is present in an amount of 10 to 100 vol % based upon the total volume of the ester-containing substrate, preferably 15 to 95 vol % based upon the total volume of the ester-containing substrate, more preferably 20 to 90 vol % based upon the total volume of the ester-containing substrate (e.g. 50 vol % based upon the total volume of the ester-containing substrate).

    [0052] In preferred processes of the present invention, the volume ratio of the at least one solvent to the ester-containing substrate is less than or equal to 1:1, preferably less than or equal to 1:2.

    [0053] In preferred processes of the present invention, the volume ratio of the at least one solvent to the ester-containing substrate is in the range 1:2 to 1:1, preferably in the range 1:2 to 1:1.5.

    [0054] In preferred processes of the present invention, the process is carried out in the presence of more than one solvent. Preferred solvents are as described above.

    [0055] In alternative preferred processes of the present invention, the process is carried out in the presence of a first solvent and a second solvent.

    [0056] In preferred processes of the present invention, the first solvent is selected from toluene, THF and Me-THF. In preferred processes of the present invention, the second solvent is an alcohol, preferably ethanol.

    [0057] In particularly preferred processes of the present invention, the first solvent is toluene and the second solvent is an alcohol, preferably ethanol.

    [0058] In alternative particularly preferred processes of the present invention, the first solvent is THF and the second solvent is an alcohol, preferably ethanol.

    [0059] In preferred processes of the present invention, the first solvent is present in an amount of 10 to 100 vol % based upon the total volume of the ester-containing substrate, preferably 15 to 95 vol % based upon the total volume of the ester-containing substrate, more preferably 20 to 90 vol % based upon the total volume of the ester-containing substrate (e.g. 50 vol % based upon the total volume of the ester-containing substrate).

    [0060] In preferred processes of the present invention, the volume ratio of the first solvent to the ester-containing substrate is less than or equal to 1:1, preferably less than or equal to 1:2.

    [0061] In preferred processes of the present invention, the volume ratio of the first solvent to the ester-containing substrate is in the range 1:2 to 1:1, preferably in the range 1:2 to 1:1.5.

    [0062] In preferred processes of the present invention, the second solvent is present in an amount of 1 to 15 vol % based upon the total volume of ester-containing substrate, preferably in an amount of 1 to 10 vol % based upon the total volume of ester-containing substrate, preferably in an amount of 1 to 7.5 vol % based upon the total volume of the ester-containing substrate, more preferably in an amount of 1 to 5 vol % based upon the total volume of the ester-containing substrate.

    [0063] In preferred processes of the present invention, the first solvent is present in an amount of 10 to 100 vol % based upon the total volume of the ester-containing substrate and the second solvent is present in an amount of 1 to 10 vol % based upon the total volume of ester-containing substrate, preferably the first solvent is present in an amount of 15 to 95 vol % based upon the total volume of the ester-containing substrate and the second solvent is present in an amount of 1 to 7.5 vol % based upon the total volume of the ester-containing substrate, more preferably the first solvent is present in an amount of 20 to 90 vol % based upon the total volume of the ester-containing substrate and the second solvent is present in an amount of 1 to 5 vol % based upon the total volume of the ester-containing substrate.

    [0064] In preferred processes of the present invention, the process is conducted at a temperature in the range 20 to 150° C., more preferably in the range 20 to 140° C., more preferably in the range 25 to 130° C., more preferably in the range 25 to 120° C., more preferably in the range 30 to 100° C., more preferably in the range 30 to 90° C., more preferably in the range 30 to 80° C., more preferably in the range 35 to 75° C., even more preferably in the range 37.5 to 60° C., even more preferably in the range 40 to 55° C., and most preferably in the range 40 to 50° C. (e.g. 40° C.). The preferred processes of the present invention are conducted at relatively low temperatures, meaning that the processes are more economical because the energy input to the reaction is lower. It is thought that lower temperatures for the ester hydrogenation may also help to improve catalyst stability.

    [0065] Preferred processes of the present invention are conducted at a pressure that is at least 5 bar, more preferably at least 10 bar, even more preferably at least 20 bar, even more preferably at least 30 bar, even more preferably at least 40 bar, and most preferably at least 50 bar.

    [0066] Preferred processes of the present invention are conducted at a pressure that is in the range 5 to 100 bar, more preferably in the range 10 to 95 bar, even more preferably in the range 20 to 90 bar, even more preferably in the range 25 to 70 bar, and most preferably in the range 30 to 50 bar.

    [0067] Preferred processes of the present invention are conducted for a duration of 1 to 24 hours, more preferably 2 to 16 hours, even more preferably 3 to 10 hours, and most preferably 4 to 8 hours.

    [0068] The processes of the present invention require a low catalyst loading, whilst still achieving an industrially useful TON and conversion for the ester hydrogenation. A lower catalyst loading means that the reactions are greener and more efficient. A lower catalyst loading also means that the cost of the reaction can be reduced.

    [0069] In the process of the present invention, the substrate/catalyst loading is greater than or equal to 10,000/1. In preferred processes of the present invention, the substrate/catalyst loading is greater than or equal to 20,000/1, even more preferably greater than or equal to 30,000/1, even more preferably greater than or equal to 40,000/1, even more preferably greater than or equal to 50,000/1, even more preferably greater than or equal to 60,000/1, even more preferably greater than or equal to 70,000/1, even more preferably greater than or equal to 80,000/1, even more preferably greater than or equal to 90,000/1, even more preferably greater than or equal to 100,000/1, even more preferably greater than or equal to 200,000/1, even more preferably greater than or equal to 300,000/1, even more preferably greater than or equal to 400,000/1, even more preferably greater than or equal to 500,000/1, even more preferably greater than or equal to 600,000/1, even more preferably greater than or equal to 700,000/1, even more preferably greater than or equal to 800,000/1, even more preferably greater than or equal to 900,000/1, even more preferably greater than or equal to 1,000,000/1.

    [0070] In some embodiments of the process of the present invention, the substrate/catalyst loading is less than or equal to 2,000,000/1.

    [0071] The process of the present invention employs a transition metal catalyst. The transition metal catalyst may be pre-formed or may be formed in situ during the ester hydrogenation reaction. Preferably, the transition metal catalyst is pre-formed. Alternatively, the transition metal catalyst is formed in situ during the ester hydrogenation reaction.

    [0072] In preferred processes of the present invention, the transition metal in the transition metal catalyst is a Group 6, Group 7, Group 8, or Group 9 transition metal. More preferably, the transition metal in the transition metal catalyst is a Group 7, Group 8, or Group 9 transition metal. Even more preferably, the transition metal in the transition metal catalyst is a Group 8 transition metal.

    [0073] In preferred processes of the present invention, the transition metal in the transition metal catalyst is selected from Mo, Mn, Fe, Ru, Co and Os. More preferably, the transition metal in the transition metal catalyst is selected from Ru and Os. Most preferably, the transition metal in the transition metal catalyst is Ru.

    [0074] In preferred processes of the present invention, the transition metal catalyst employed in the process of the present invention comprises a tridentate ligand.

    [0075] In preferred processes of the present invention, the transition metal catalyst comprises a tridentate ligand having a Formula (I)

    ##STR00001##

    wherein: [0076] X is selected from —SR.sup.a, —OR.sup.a, —CR.sup.a, —NR.sup.aR.sup.b, —PR.sup.aR.sup.b, —P(═O)R.sup.aR.sup.b, —OPR.sup.aR.sup.b, and —NHPR.sup.aR.sup.b; [0077] R.sup.1 and R.sup.x are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl, or R.sup.1 and one of R.sup.3a and R.sup.3b or R.sup.x and one of R.sup.3a and R.sup.3b together with the atoms to which they are bound, form a ring; [0078] or X is a heteroatom and when taken together with R.sup.1 it forms an optionally substituted heterocycle when R.sup.x is absent; [0079] Y is selected from —SR.sup.a, —OR.sup.a, —CR.sup.a, —NR.sup.aR.sup.b, —PR.sup.aR.sup.b, —P(═O)R.sup.aR.sup.b, —OPR.sup.aR.sup.b, and —NHPR.sup.aR.sup.b; [0080] R.sup.2 and R.sup.y are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl, or R.sup.2 and one of R.sup.4a and R.sup.4b or R.sup.y and one of R.sup.4a and R.sup.4b together with the atoms to which they are bound, form a ring; [0081] or Y is a heteroatom and when taken together with R.sup.2 it forms an optionally substituted heterocycle when R.sup.y is absent; [0082] R.sup.3a, R.sup.3b, R.sup.4a, and R.sup.4b are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl, or R.sup.3a and one of R.sup.4a and R.sup.4b or R.sup.3b and one of R.sup.4a and R.sup.4b together with the atoms to which they are bound, form a heterocycle; [0083] R.sup.5 is selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; [0084] each m and n is independently 1 or 2; and [0085] R.sup.a and R.sup.b, if present, are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.5-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; or when X and/or Y is —NR.sup.aR.sup.b, —PR.sup.aR.sup.b, —OPR.sup.aR.sup.b, or —NHPR.sup.aR.sup.b, R.sup.a and R.sup.b together with the heteroatom to which they are attached form a heterocycle.

    [0086] In tridentate ligands of Formula (I), X is preferably selected from —SR.sup.a, —CR.sup.a, —NR.sup.aR.sup.b, —PR.sup.aR.sup.b, and —NHPR.sup.aR.sup.b. More preferably, X is selected from —SR.sup.a, —PR.sup.aR.sup.b, and —NHPR.sup.aR.sup.b. Even more preferably, X is selected from —SR.sup.a and —PR.sup.aR.sup.b. Most preferably, X is —SR.sup.a.

    [0087] In tridentate ligands of Formula (I), R.sup.1 and R.sup.x are each independently preferably selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.1-20-heteroalkyl and substituted or unsubstituted C.sub.3-20-cycloalkyl. More preferably, R.sup.1 and R.sup.x are each independently selected from hydrogen and substituted or unsubstituted C.sub.1-20-alkyl. Even more preferably, R.sup.1 and R.sup.x are each hydrogen.

    [0088] In alternative preferred tridentate ligands of Formula (I), X is a heteroatom and when taken together with R.sup.1 it forms an optionally substituted heterocycle when R.sup.x is absent. More preferably, X is a heteroatom and when taken together with R.sup.1 it forms an optionally substituted heteroaromatic ring when R.sup.x is absent. More preferably, the optionally substituted heteroaromatic ring is an optionally substituted nitrogen-containing heteroaromatic ring. Even more preferably, the optionally substituted nitrogen-containing heteroaromatic ring is selected from pyridinyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, oxazolyl, isoxazolyl, triazolyl, tetrazolyl, thiadiazolyl, oxadiazolyl, pyrimidyl, benzoxazolyl, benzthiazolyl, benzimidazolyl, indolyl, and quinolinyl. Even more preferably, the optionally substituted nitrogen-containing heteroaromatic ring is selected from pyridinyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl, and pyrimidyl. Most preferably, the optionally substituted nitrogen-containing heteroaromatic ring is pyridinyl.

    [0089] In tridentate ligands of Formula (I), Y is preferably selected from —SR.sup.a, —CR.sup.a, —NR.sup.aR.sup.b, —PR.sup.aR.sup.b, and —NHPR.sup.aR.sup.b. More preferably, Y is selected from —SR.sup.a, —PR.sup.aR.sup.b, and —NHPR.sup.aR.sup.b. Even more preferably, Y is selected from —SR.sup.a and —PR.sup.aR.sup.b. Most preferably, Y is —SR.sup.a.

    [0090] In tridentate ligands of Formula (I), R.sup.2 and R.sup.y are each independently preferably selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.1-20-heteroalkyl and substituted or unsubstituted C.sub.3-20-cycloalkyl. More preferably, R.sup.2 and R.sup.y are each independently selected from hydrogen and substituted or unsubstituted C.sub.1-20-alkyl. Even more preferably, R.sup.2 and R.sup.y are each hydrogen.

    [0091] In alternative preferred tridentate ligands of Formula (I), Y is a heteroatom and when taken together with R.sup.2 it forms an optionally substituted heterocycle when R.sup.y is absent. More preferably, Y is a heteroatom and when taken together with R.sup.2 it forms an optionally substituted heteroaromatic ring when R.sup.y is absent. More preferably, the optionally substituted heteroaromatic ring is an optionally substituted nitrogen-containing heteroaromatic ring. Even more preferably, the optionally substituted nitrogen-containing heteroaromatic ring is selected from pyridinyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, oxazolyl, isoxazolyl, triazolyl, tetrazolyl, thiadiazolyl, oxadiazolyl, pyrimidyl, benzoxazolyl, benzthiazolyl, benzimidazolyl, indolyl, and quinolinyl. Even more preferably, the optionally substituted nitrogen-containing heteroaromatic ring is selected from pyridinyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl, and pyrimidyl. Most preferably, the optionally substituted nitrogen-containing heteroaromatic ring is pyridinyl.

    [0092] In tridentate ligands of Formula (I), R.sup.3a, R.sup.3b, R.sup.4a, and R.sup.4b are each independently preferably selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.1-20-heteroalkyl and substituted or unsubstituted C.sub.3-20-cycloalkyl. More preferably, R.sup.3a, R.sup.3b, R.sup.4a, and R.sup.4b are each independently selected from hydrogen and substituted or unsubstituted C.sub.1-20-alkyl. Even more preferably, R.sup.3a, R.sup.3b, R.sup.4a, and R.sup.4b are each hydrogen.

    [0093] In alternative preferred tridentate ligands of Formula (I), R.sup.3a and one of R.sup.4a and R.sup.4b or R.sup.3b and one of R.sup.4a and R.sup.4b together with the atoms to which they are bound, form a heterocycle. Preferably, the heterocycle is a six-membered ring heterocycle.

    [0094] In tridentate ligands of Formula (I), R.sup.5 is preferably selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.1-20-heteroalkyl and substituted or unsubstituted C.sub.3-20-cycloalkyl. More preferably, R.sup.5 is selected from hydrogen and substituted or unsubstituted C.sub.1-20-alkyl. Even more preferably, R.sup.5 is hydrogen.

    [0095] In tridentate ligands of Formula (I), each m and n is preferably 1.

    [0096] In tridentate ligands of Formula (I), R.sup.a and R.sup.b, if present, are each independently preferably selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl. More preferably, R.sup.a and R.sup.b, if present, are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl (e.g. C.sub.1-10-alkyl) and substituted or unsubstituted C.sub.6-20-aryl. Particularly preferred C.sub.1-20-alkyl groups include ethyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, tert-butyl, pentyl, and hexyl, more preferably methyl, ethyl, iso-propyl, tert-butyl, even more preferably ethyl. Preferred C.sub.6-20-aryl groups include phenyl, tolyl, xylyl, and methoxyphenyl, more preferably phenyl.

    [0097] In alternative preferred tridentate ligands of Formula (I), when X and/or Y is —NR.sup.aR.sup.b, —PR.sup.aR.sup.b, —OPR.sup.aR.sup.b, or —NHPR.sup.aR.sup.b, R.sup.a and R.sup.b together with the heteroatom to which they are attached form a heterocycle.

    [0098] In preferred processes of the present invention, the transition metal catalyst comprises a tridentate ligand having a Formula (I) wherein: [0099] X is selected from —SR.sup.a, —CR.sup.a, —NR.sup.aR.sup.b, —PR.sup.aR.sup.b, and —NHPR.sup.aR.sup.b; [0100] R.sup.1 and R.sup.x are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; [0101] or X is a heteroatom and when taken together with R.sup.1 it forms an optionally substituted heteroaromatic ring when R.sup.x is absent, wherein the heteroaromatic ring is a nitrogen-containing heteroaromatic ring; [0102] Y is selected from —SR.sup.a, —CR.sup.a, —NR.sup.aR.sup.b, —PR.sup.aR.sup.b, and —NHPR.sup.aR.sup.b; [0103] R.sup.2 and R.sup.y are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; [0104] or Y is a heteroatom and when taken together with R.sup.2 it forms an optionally substituted heteroaromatic ring when R.sup.y is absent, wherein the heteroaromatic ring is a nitrogen-containing heteroaromatic ring; [0105] R.sup.3a, R.sup.3b, R.sup.4a, R.sup.4b and R.sup.5 are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; each m and n is independently 1 or 2; and [0106] R.sup.a and R.sup.b, if present, are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.5-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; or when X and/or Y is —NR.sup.aR.sup.b, —PR.sup.aR.sup.b or —NHPR.sup.aR.sup.b, R.sup.a and R.sup.b together with the heteroatom to which they are attached form a heterocycle.

    [0107] In preferred processes of the present invention, the transition metal catalyst comprises a tridentate ligand having a Formula (I) wherein: [0108] X is selected from —SR.sup.a, —PR.sup.aR.sup.b, and —NHPR.sup.aR.sup.b; [0109] R.sup.1 and R.sup.x are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; [0110] or X is a heteroatom and when taken together with R.sup.1 it forms an optionally substituted heteroaromatic ring when R.sup.x is absent, wherein the heteroaromatic ring is a nitrogen-containing heteroaromatic ring selected from pyridinyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, oxazolyl, isoxazolyl, triazolyl, tetrazolyl, thiadiazolyl, oxadiazolyl, pyrimidyl, benzoxazolyl, benzthiazolyl, benzimidazolyl, indolyl, and quinolinyl; [0111] Y is selected from —SR.sup.a, —PR.sup.aR.sup.b, and —NHPR.sup.aR.sup.b; [0112] R.sup.2 and R.sup.y are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; [0113] or Y is a heteroatom and when taken together with R.sup.2 it forms an optionally substituted heteroaromatic ring when R.sup.y is absent, wherein the heteroaromatic ring is a nitrogen-containing heteroaromatic ring selected from pyridinyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, oxazolyl, isoxazolyl, triazolyl, tetrazolyl, thiadiazolyl, oxadiazolyl, pyrimidyl, benzoxazolyl, benzthiazolyl, benzimidazolyl, indolyl, and quinolinyl; [0114] R.sup.3, R.sup.3b, R.sup.4a, R.sup.4b and R.sup.5 are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; [0115] each m and n is independently 1 or 2; and [0116] R.sup.a and R.sup.b, if present, are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.5-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; or when X and/or Y is —PR.sup.aR.sup.b or —NHPR.sup.aR.sup.b, R.sup.a and R.sup.b together with the heteroatom to which they are attached form a heterocycle.

    [0117] In preferred processes of the present invention, the transition metal catalyst comprises a tridentate ligand having a Formula (I) [0118] wherein: [0119] X is selected from —SR.sup.a and —PR.sup.aR.sup.b; [0120] R.sup.1 and R.sup.x are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; [0121] or X is a heteroatom and when taken together with R.sup.1 it forms an optionally substituted heteroaromatic ring when R.sup.x is absent, wherein the heteroaromatic ring is a nitrogen-containing heteroaromatic ring selected from pyridinyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl, and pyrimidyl; [0122] Y is selected from —SR.sup.a and —PR.sup.aR.sup.b; [0123] R.sup.2 and R.sup.y are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; [0124] or Y is a heteroatom and when taken together with R.sup.2 it forms an optionally substituted heteroaromatic ring when R.sup.y is absent, wherein the heteroaromatic ring is a nitrogen-containing heteroaromatic ring selected from pyridinyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl, and pyrimidyl; [0125] R.sup.3, R.sup.3b, R.sup.4a, R.sup.4b and R.sup.5 are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.5-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; each m and n is independently 1 or 2; and [0126] R.sup.a and R.sup.b, if present, are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.5-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; or when X and/or Y is —PR.sup.aR.sup.b, R.sup.a and R.sup.b together with the heteroatom to which they are attached form a heterocycle.

    [0127] In preferred processes of the present invention, the transition metal catalyst comprises a tridentate ligand having a Formula (I), wherein: [0128] X is —SR.sup.a; [0129] R.sup.1 and R.sup.x are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; [0130] Y is —SR.sup.a; [0131] R.sup.2 and R.sup.y are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; [0132] R.sup.3a, R.sup.3b, R.sup.4a, R.sup.4b and R.sup.5 are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; each m and n is independently 1 or 2; and [0133] R.sup.a are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.5-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl.

    [0134] Preferably, the transition metal catalyst comprises a tridentate ligand having a Formula (I), wherein: [0135] X is —SR.sup.a; [0136] R.sup.1 and R.sup.x are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, and substituted or unsubstituted C.sub.3-20-cycloalkyl; [0137] Y is —SR.sup.a; [0138] R.sup.2 and R.sup.y are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, and substituted or unsubstituted C.sub.3-20-cycloalkyl; [0139] R.sup.3a, R.sup.3b, R.sup.4a, R.sup.4b and R.sup.5 are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, and substituted or unsubstituted C.sub.3-20-cycloalkyl; [0140] each m and n is independently 1 or 2; and R.sup.a are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, and substituted or unsubstituted C.sub.3-20-cycloalkyl.

    [0141] More preferably, the transition metal catalyst comprises a tridentate ligand having a Formula (I), wherein: [0142] X is —SR.sup.a; [0143] R.sup.1 and R.sup.x are each independently selected from hydrogen and substituted or unsubstituted C.sub.1-20-alkyl; [0144] Y is —SR.sup.a; [0145] R.sup.2 and R.sup.y are each independently selected from hydrogen and substituted or unsubstituted C.sub.1-20-alkyl; [0146] R.sup.3, R.sup.3b, R.sup.4a, R.sup.4b and R.sup.5 are each independently selected from hydrogen and substituted or unsubstituted C.sub.1-20-alkyl; [0147] each m and n is independently 1 or 2; and [0148] R.sup.a are each independently selected from hydrogen and substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, and substituted or unsubstituted C.sub.3-20-cycloalkyl.

    [0149] Even more preferably, the transition metal catalyst comprises a tridentate ligand having a Formula (I), wherein: [0150] X and Y are each —SR.sup.a; [0151] R.sup.1, R.sup.x, R.sup.2, R.sup.y, R.sup.3a, R.sup.3b, R.sup.4a, R.sup.4b and R.sup.5 are each hydrogen; [0152] m and n are each 1; and [0153] R.sup.a are each independently substituted or unsubstituted C.sub.1-20-alkyl, preferably C.sub.1-10 alkyl.

    [0154] Even more preferably, the transition metal catalyst comprises a tridentate ligand having a Formula (I), wherein: [0155] X and Y are each -SEt; [0156] R.sup.1, R.sup.x, R.sup.2, R.sup.y, R.sup.3a, R.sup.3b, R.sup.4a, R.sup.4b and R.sup.5 are each hydrogen; and [0157] m and n are each 1.

    [0158] In alternative preferred processes of the present invention, the transition metal catalyst comprises a tridentate ligand having a Formula (I), wherein: [0159] X is a heteroatom and when taken together with R.sup.1 it forms an optionally substituted heteroaromatic ring when R.sup.x is absent; [0160] Y is —PR.sup.aR.sup.b; [0161] R.sup.2 and R.sup.y are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; [0162] R.sup.3a, R.sup.3b, R.sup.4a, R.sup.4b and R.sup.5 are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; each m and n is independently 1 or 2; and [0163] R.sup.a and R.sup.b are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; or R.sup.a and R.sup.b together with the heteroatom to which they are attached form a heterocycle.

    [0164] Preferably, the transition metal catalyst comprises a tridentate ligand having a Formula (I), wherein: [0165] X is a nitrogen atom and when taken together with R.sup.1 it forms an optionally substituted heteroaromatic ring when R.sup.x is absent, wherein the heteroaromatic ring is a nitrogen-containing heteroaromatic ring; [0166] Y is —PR.sup.aR.sup.b; [0167] R.sup.2 and R.sup.y are each independently is selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, and substituted or unsubstituted C.sub.3-20-cycloalkyl; [0168] R.sup.3a, R.sup.3b, R.sup.4a, R.sup.4b and R.sup.5 are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.3-20-cycloalkyl; [0169] each m and n is independently 1 or 2; and [0170] R.sup.a and R.sup.b are each independently selected from substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.5-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl.

    [0171] More preferably, the transition metal catalyst comprises a tridentate ligand having a Formula (I), wherein: [0172] X is a nitrogen atom and when taken together with R.sup.1 it forms an optionally substituted heteroaromatic ring when R.sup.x is absent, wherein the heteroaromatic ring is a nitrogen-containing heteroaromatic ring selected from pyridinyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, oxazolyl, isoxazolyl, triazolyl, tetrazolyl, thiadiazolyl, oxadiazolyl, pyrimidyl, benzoxazolyl, benzthiazolyl, benzimidazolyl, indolyl, and quinolinyl; [0173] Y is —PR.sup.aR.sup.b; [0174] R.sup.2, R.sup.y, R.sup.3a, R.sup.3b, R.sup.4a, R.sup.4b and R.sup.5 are each hydrogen; [0175] each m and n is 1; and [0176] R.sup.a and R.sup.b are each independently selected from substituted or unsubstituted C.sub.1-20-alkyl and substituted or unsubstituted C.sub.6-20-aryl.

    [0177] Even more preferably, the transition metal catalyst comprises a tridentate ligand having a Formula (I), wherein: [0178] X is a nitrogen atom and when taken together with R.sup.1 it forms an optionally substituted heteroaromatic ring when R.sup.x is absent, wherein the heteroaromatic ring is a nitrogen-containing heteroaromatic ring selected from pyridinyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl, and pyrimidyl; [0179] Y is —PR.sup.aR.sup.b; [0180] R.sup.2, R.sup.y, R.sup.3a, R.sup.3b, R.sup.4a, R.sup.4b and R.sup.5 are each hydrogen; [0181] each m and n is 1; and [0182] R.sup.a and R.sup.b are each independently selected from methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, phenyl, tolyl, xylyl, and methoxyphenyl.

    [0183] Even more preferably, the transition metal catalyst comprises a tridentate ligand having a Formula (I), wherein: [0184] X is a nitrogen atom and when taken together with R.sup.1 it forms an optionally substituted pyridinyl ring when R.sup.x is absent; [0185] Y is —PR.sup.aR.sup.b; [0186] R.sup.2, R.sup.y, R.sup.3a, R.sup.3b, R.sup.4a, R.sup.4b and R.sup.5 are each hydrogen; [0187] each m and n is 1; and [0188] R.sup.a and R.sup.b are each independently selected from methyl, ethyl, iso-propyl, tert-butyl, phenyl, tolyl, xylyl, and methoxyphenyl.

    [0189] Even more preferably, the transition metal catalyst comprises a tridentate ligand having a Formula (I), wherein: [0190] X is a nitrogen atom and when taken together with R.sup.1 it forms an optionally substituted pyridinyl ring when R.sup.x is absent; [0191] Y is —PR.sup.aR.sup.b; [0192] R.sup.2, R.sup.y, R.sup.3a, R.sup.3b, R.sup.4a, R.sup.4b and R.sup.5 are each hydrogen; [0193] each m and n is 1; and [0194] R.sup.a and R.sup.b are each phenyl.

    [0195] In preferred processes of the present invention, the transition metal catalyst has a Formula (II) or Formula (III)


    [M(L.sup.1)(L.sup.2).sub.d]  (II)


    [M(L.sup.1)(L.sup.2).sub.d]W  (III)

    wherein: [0196] M is a transition metal; [0197] L.sup.1 is a tridentate ligand as hereinbefore defined; [0198] L.sup.2 are ligands which may be the same or different; [0199] d is 1, 2 or 3; and [0200] W is a non-coordinated anionic ligand.

    [0201] In preferred processes of the present invention, M is a Group 6, Group 7, Group 8, or Group 9 transition metal. More preferably, M is a Group 7, Group 8, or Group 9 transition metal. Even more preferably, M is a Group 8 transition metal.

    [0202] In preferred processes of the present invention, M is a transition metal selected from Mo, Mn, Fe, Ru, Co and Os. More preferably, M is a transition metal selected from Ru and Os. Most preferably, M is Ru.

    [0203] In preferred processes of the present invention, d is 3.

    [0204] As will be understood by a skilled person, each L.sup.2 may be a monodentate ligand or a multidentate ligand, provided the combination of L.sup.2 ligands is allowed by the rules of valency. In preferred processes of the present invention, each L.sup.2 is a monodentate ligand. Preferably, each L.sup.2 is independently a neutral monodentate ligand or an anionic monodentate ligand. In preferred processes of the present invention, each L.sup.2 is independently selected from —H, —CO, —CN, —P(R′).sub.3, —As(R′).sub.3, —CR′, —OR′, —O(C═O)R′, —NR′.sub.2, halogen (e.g. —Cl, —Br, —I), and solvent, wherein each R′ is independently selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl. Preferably, each L.sup.2 is independently selected from —H, —CO, —P(R′).sub.3, and halogen. More preferably, each L.sup.2 is independently selected from —CO, —PPh.sub.3, and —Cl. When L.sup.2 is solvent, the solvent is preferably selected from THF, Me-THF, MeCN, H.sub.2O and an alcohol (e.g. methanol, ethanol, iso-propanol etc.).

    [0205] In the transition metal catalysts of formula (III), W is a non-coordinated anionic ligand. By “non-coordinated anion ligand”, we mean the anionic ligand is forced to the outer sphere of the metal centre. The anionic ligand, therefore, is dissociated from the metal centre. This is in contrast to neutral complexes in which the anionic ligand is bound to the metal within the coordination sphere. The anionic ligand can be generally identified as non-coordinating by analysing the X-ray crystal structure of the cationic complex. Preferably, W is selected from the group consisting of triflate (i.e. TfO.sup.− or CF.sub.3SO.sub.3.sup.−), tetrafluoroborate (i.e. —BF.sub.4), hexafluoroantimonate (i.e. —SbF.sub.6), hexafluorophosphate (PF.sub.6.sup.−), [B[3,5-(CF.sub.3).sub.2C.sub.6H.sub.3].sub.4].sup.− ([BAr.sup.F.sub.4].sup.+), halide (e.g. Cl.sup.−, Br.sup.−, I.sup.−) and mesylate (MsO.sup.− or MeSO.sub.3.sup.−).

    [0206] Preferably, the transition metal catalyst is a transition metal catalyst of Formula (II).

    [0207] Alternatively, the transition metal catalyst is a transition metal catalyst of Formula (III).

    [0208] In preferred processes of the present invention, the transition metal catalyst is

    ##STR00002##

    [0209] In preferred processes of the present invention, the transition metal catalyst is Ru-SNS or Ru-PNN.

    [0210] In preferred processes of the present invention, the transition metal catalyst is

    ##STR00003##

    [0211] In preferred processes of the present invention, the transition metal catalyst employed in the processes of the present invention comprises a bidentate ligand.

    [0212] In preferred processes of the present invention, the transition metal catalyst comprises a bidentate ligand having a Formula (IV)

    ##STR00004## [0213] wherein: [0214] X′ is —NHR.sup.ax; [0215] Y′ is selected from —SR.sup.ax, —OR.sup.ax, —CR.sup.ax, —NR.sup.axR.sup.bx, —PR.sup.axR.sup.bx, —P(═O)R.sup.axR.sup.bx, —OPR.sup.axR.sup.bx, and —NHPR.sup.axR.sup.bx; [0216] R.sup.8a, R.sup.8b, R.sup.9a and R.sup.9b are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.5-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; [0217] p is 1 or 2; and [0218] R.sup.ax and R.sup.bx, if present, are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; or when X′ and/or Y′ is —NR.sup.axR.sup.bx, —PR.sup.axR.sup.bx, —OPR.sup.axR.sup.bx, or —NHPR.sup.axR.sup.bx, R.sup.ax and R.sup.bx together with the heteroatom to which they are attached form a heterocycle.

    [0219] In preferred processes of the present invention, the transition metal catalyst has a Formula (V) or Formula (VI)


    [M(L.sup.1).sub.e(L.sup.2).sub.f]  (V)


    [M(L.sup.1).sub.e(L.sup.2).sub.f]W  (VI) [0220] wherein: [0221] M is a transition metal; [0222] L.sup.1 are bidentate ligands as hereinbefore defined which may be the same or different; [0223] L.sup.2, if present, are ligands which may be the same or different; [0224] e is 1 or 2 such that when e is 1, f is 2, 3 or 4, and when e is 2, f is 0, 1 or 2; and [0225] W is a non-coordinated anionic ligand.

    [0226] M, L.sup.2 and W are as generally described above.

    [0227] In preferred processes of the present invention, the transition metal catalyst employed in the processes of the present invention comprises a tetradentate ligand.

    [0228] In preferred processes of the present invention, the transition metal catalyst comprises a tetradentate ligand having a Formula (VII)

    ##STR00005## [0229] wherein: [0230] Q is selected from —SR.sup.ay, —OR.sup.y, —CR.sup.ay, —NR.sup.ayR.sup.by, —PR.sup.ayR.sup.by, —P(═O)R.sup.ayR.sup.by, —OPR.sup.ayR.sup.by, and —NHPR.sup.ayR.sup.by; [0231] R.sup.15 and R.sup.q are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; [0232] or Q is a heteroatom and when taken together with R.sup.15 it forms an optionally substituted heterocycle when R.sup.q is absent; [0233] W is selected from S, O, NR.sup.a, and PR.sup.a; [0234] R.sup.16, R.sup.w and R.sup.Z are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; [0235] or R.sup.16 when taken together with R.sup.Z forms an optionally substituted heterocycle when R.sup.w is absent; [0236] Z is selected from —SR.sup.ay, —OR.sup.ay, —CR.sup.ay, —NR.sup.ayR.sup.by, —PR.sup.ayR.sup.by, —P(═O)R.sup.ayR.sup.by, —OPR.sup.aR.sup.by, and —NHPR.sup.ayR.sup.by; [0237] R.sup.10a, R.sup.10b, R.sup.11a and R.sup.11b are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; or [0238] R.sup.10a and one of R.sup.11a and R.sup.11b or R.sup.10b and one of R.sup.11a and R.sup.11b together with the atoms to which they are bound, form a heterocycle; [0239] R.sup.12a, R.sup.12b, R.sup.13a, R.sup.13b and R.sup.14 are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; each q and r is independently 1 or 2; [0240] s is 0, 1 or 2; and [0241] R.sup.ay and R.sup.by, if present, are each independently selected from hydrogen, substituted or unsubstituted C.sub.1-20-alkyl, substituted or unsubstituted C.sub.2-20-alkenyl, substituted or unsubstituted C.sub.2-20-alkynyl, substituted or unsubstituted C.sub.1-20-heteroalkyl, substituted or unsubstituted C.sub.1-20-alkoxy, substituted or unsubstituted C.sub.3-20-cycloalkyl, substituted or unsubstituted C.sub.3-20-cycloalkenyl, substituted or unsubstituted C.sub.2-20-heterocycloalkyl, substituted or unsubstituted C.sub.6-20-aryl, and substituted or unsubstituted C.sub.4-20-heteroaryl; or when Q and/or Z is —NR.sup.ayR.sup.by, —PR.sup.ayR.sup.by, —OPR.sup.ayR.sup.by, or —NHPR.sup.aR.sup.by, R.sup.ay and R.sup.by together with the heteroatom to which they are attached form a heterocycle.

    [0242] In preferred processes of the present invention, the transition metal catalyst has a Formula (VIII) or Formula (IX)


    [M(L.sup.1)(L.sup.2).sub.g]  (VIII)


    [M(L.sup.1)(L.sup.2).sub.g]  (IX)

    wherein: [0243] M is a transition metal; [0244] L.sup.1 is a tetradentate ligand as hereinbefore defined; [0245] L.sup.2, if present, are ligands which may be the same or different; [0246] g is 0, 1 or 2; and [0247] W is a non-coordinated anionic ligand.

    [0248] M, L.sup.2 and W are as generally described above.

    [0249] In preferred processes of the present invention, the transition metal catalyst is removed from the reaction mixture by a precipitation step using a co-solvent.

    [0250] In alternative preferred processes of the present invention, the transition metal catalyst is removed from the reaction mixture by distillation of the product.

    [0251] In alternative preferred processes of the present invention, the transition metal catalyst is removed from the reaction mixture by crystallisation of the product.

    [0252] In alternative preferred processes of the present invention, the transition metal catalyst is removed from the reaction mixture using a metal scavenger.

    [0253] In preferred processes of the present invention, the ester-containing substrate contains at least one ester moiety.

    [0254] In preferred processes of the present invention, the ester-containing substrate contains one ester moiety. Preferably, the ester-containing substrate is of Formula (X)

    ##STR00006##

    wherein: [0255] R.sup.6 and R.sup.7 are independently organic groups having 1-70 carbon atoms; or [0256] R.sup.6/R.sup.7 forms a ring structure with the atoms to which they are attached.

    [0257] In preferred processes of the present invention, R.sup.6 and R.sup.7 are independently organic groups having 1-70 carbon atoms.

    [0258] In preferred processes of the present invention, R.sup.6 is selected from substituted or unsubstituted C.sub.1-70-alkyl, substituted or unsubstituted C.sub.2-70-alkenyl, substituted or unsubstituted C.sub.2-70-alkynyl, substituted or unsubstituted C.sub.1-70-heteroalkyl, substituted or unsubstituted C.sub.3-70-cycloalkyl, substituted or unsubstituted C.sub.3-70-cycloalkenyl, substituted or unsubstituted C.sub.2-70-heterocycloalkyl, substituted or unsubstituted C.sub.6-70-aryl, and substituted or unsubstituted C.sub.4-70-heteroaryl, preferably substituted or unsubstituted C.sub.1-50-alkyl, substituted or unsubstituted C.sub.2-50-alkenyl, substituted or unsubstituted C.sub.2-50-alkynyl, substituted or unsubstituted C.sub.1-50-heteroalkyl, substituted or unsubstituted C.sub.3-50-cycloalkyl, substituted or unsubstituted C.sub.3-50-cycloalkenyl, substituted or unsubstituted C.sub.2-50-heterocycloalkyl, substituted or unsubstituted C.sub.6-50-aryl, and substituted or unsubstituted C.sub.4-50-heteroaryl, more preferably substituted or unsubstituted C.sub.1-30-alkyl, substituted or unsubstituted C.sub.2-30-alkenyl, substituted or unsubstituted C.sub.2-30-alkynyl, substituted or unsubstituted C.sub.1-30-heteroalkyl, substituted or unsubstituted C.sub.3-30-cycloalkyl, substituted or unsubstituted C.sub.3-30-cycloalkenyl, substituted or unsubstituted C.sub.2-30-heterocycloalkyl, substituted or unsubstituted C.sub.6-30-aryl, and substituted or unsubstituted C.sub.4-30-heteroaryl, even more preferably substituted or unsubstituted C.sub.1-20-alkyl (e.g. C.sub.3-20-alkyl), substituted or unsubstituted C.sub.2-20-alkenyl (e.g. C.sub.8-20-alkenyl), substituted or unsubstituted C.sub.2-20-alkynyl (e.g. C.sub.3-20-alkynyl), substituted or unsubstituted C.sub.1-20-heteroalkyl (e.g. C.sub.3-20-heteroalkyl), substituted or unsubstituted C.sub.3-20-cycloalkyl (e.g. C.sub.3-20-cycloalkyl), substituted or unsubstituted C.sub.3-20-cycloalkenyl (e.g. C.sub.3-20-cycloalkenyl), substituted or unsubstituted C.sub.2-20-heterocycloalkyl (e.g. C.sub.3-20-heterocycloalkyl), substituted or unsubstituted C.sub.6-20-aryl (e.g. C.sub.3-20-aryl), and substituted or unsubstituted C.sub.4-20-heteroaryl (e.g. C.sub.3-20-heteroaryl). Preferably, R.sup.6 is selected from substituted or unsubstituted C.sub.1-70-alkyl, substituted or unsubstituted C.sub.2-70-alkenyl, substituted or unsubstituted C.sub.1-70-heteroalkyl, substituted or unsubstituted C.sub.6-70-aryl, and substituted or unsubstituted C.sub.4-70-heteroaryl, more preferably substituted or unsubstituted C.sub.1-50-alkyl, substituted or unsubstituted C.sub.2-50-alkenyl, substituted or unsubstituted C.sub.1-50-heteroalkyl, substituted or unsubstituted C.sub.6-50-aryl, and substituted or unsubstituted C.sub.4-50-heteroaryl, even more preferably substituted or unsubstituted C.sub.1-30-alkyl, substituted or unsubstituted C.sub.2-30-alkenyl, substituted or unsubstituted C.sub.1-30-heteroalkyl, substituted or unsubstituted C.sub.6-30-aryl, and substituted or unsubstituted C.sub.4-30-heteroaryl, even more preferably substituted or unsubstituted C.sub.1-20-alkyl (e.g. C.sub.3-20-alkyl), substituted or unsubstituted C.sub.2-20-alkenyl (e.g. C.sub.8-20-alkenyl), substituted or unsubstituted C.sub.1-20-heteroalkyl (e.g. C.sub.3-20-heteroalkyl), substituted or unsubstituted C.sub.6-20-aryl (e.g. C.sub.8-20-aryl), and substituted or unsubstituted C.sub.4-20-heteroaryl (e.g. C.sub.3-20-heteroaryl). More preferably, R.sup.6 is selected from substituted or unsubstituted C.sub.1-70-alkyl, substituted or unsubstituted C.sub.2-70-alkenyl, and substituted or unsubstituted C.sub.6-70-aryl, more preferably substituted or unsubstituted C.sub.1-50-alkyl, substituted or unsubstituted C.sub.2-50-alkenyl, and substituted or unsubstituted C.sub.6-50-aryl, even more preferably substituted or unsubstituted C.sub.1-30-alkyl, substituted or unsubstituted C.sub.2-30-alkenyl, and substituted or unsubstituted C.sub.6-30-aryl, even more preferably substituted or unsubstituted C.sub.1-20-alkyl (e.g. C.sub.3-20-alkyl), substituted or unsubstituted C.sub.2-20-alkenyl (e.g. C.sub.3-20-alkenyl), and substituted or unsubstituted C.sub.6-20-aryl (e.g. C.sub.3-20-aryl). More preferably, R.sup.6 is selected from substituted or unsubstituted C.sub.1-70-alkyl and substituted or unsubstituted C.sub.6-70-aryl, more preferably substituted or unsubstituted C.sub.1-50-alkyl and substituted or unsubstituted C.sub.6-50-aryl, even more preferably substituted or unsubstituted C.sub.1-30-alkyl and substituted or unsubstituted C.sub.6-30-aryl, even more preferably substituted or unsubstituted C.sub.1-20-alkyl (e.g. C.sub.3-20-alkyl) and substituted or unsubstituted C.sub.6-20-aryl (e.g. C.sub.3-20-aryl). Even more preferably, R.sup.6 is selected from methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, phenyl, tolyl, xylyl, and methoxyphenyl.

    [0259] In alternative preferred processes of the present invention, R.sup.6 is an aliphatic group containing at least 9 carbon atoms. Preferably, R.sup.6 is selected from substituted or unsubstituted C.sub.9-70-alkyl, substituted or unsubstituted C.sub.9-70-alkenyl, substituted or unsubstituted C.sub.9-70-cycloalkyl, and substituted or unsubstituted C.sub.9-70-cycloalkenyl, more preferably substituted or unsubstituted C.sub.9-50-alkyl, substituted or unsubstituted C.sub.9-50-alkenyl, substituted or unsubstituted C.sub.9-50-cycloalkyl, and substituted or unsubstituted C.sub.9-50-cycloalkenyl, more preferably substituted or unsubstituted C.sub.9-30-alkyl, substituted or unsubstituted C.sub.9-30-alkenyl, substituted or unsubstituted C.sub.9-30-cycloalkyl, and substituted or unsubstituted C.sub.9-30-cycloalkenyl, even more preferably substituted or unsubstituted C.sub.9-20-alkyl, substituted or unsubstituted C.sub.9-20-alkenyl, substituted or unsubstituted C.sub.9-20-cycloalkyl, and substituted or unsubstituted C.sub.9-20-cycloalkenyl.

    [0260] In preferred processes of the present invention, R.sup.7 is selected from substituted or unsubstituted C.sub.1-70-alkyl or substituted or unsubstituted C.sub.6-70-aryl, preferably substituted or unsubstituted C.sub.1-50-alkyl or substituted or unsubstituted C.sub.6-50-aryl, more preferably substituted or unsubstituted C.sub.1-30-alkyl or substituted or unsubstituted C.sub.6-30-aryl, even more preferably substituted or unsubstituted C.sub.1-20-alkyl (e.g. C.sub.3-20-alkyl) or substituted or unsubstituted C.sub.6-20-aryl (e.g. C.sub.3-20-aryl). Preferably, R.sup.7 is selected from substituted or unsubstituted C.sub.1-70-alkyl, more preferably substituted or unsubstituted C.sub.1-50-alkyl, even more preferably substituted or unsubstituted C.sub.1-30-alkyl, even more preferably substituted or unsubstituted C.sub.1-20-alkyl (e.g. C.sub.8-20-alkyl). More preferably, R.sup.7 is selected from methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, and octyl.

    [0261] In preferred processes of the present invention, the ester-containing substrate is a methyl ester (e.g. methyl acetate).

    [0262] In preferred processes of the present invention, the ester-containing substrate is an ethyl ester (e.g. ethyl acetate).

    [0263] In preferred processes of the present invention, the ester-containing substrate is a wax ester.

    [0264] In preferred processes of the present invention, R.sup.6/R.sup.7 forms a ring structure with the atoms to which they are attached (i.e. the ring structure is a lactone). Preferably, the ring structure is a 4 to 7 membered ring system. More preferably, the ring structure is a 5 to 6 membered ring system.

    [0265] In preferred processes of the present invention, the ester-containing substrate contains more than one ester moiety, preferably two or three ester moieties.

    [0266] In preferred processes of the present invention, the ester-containing substrate is selected from

    ##STR00007## ##STR00008## ##STR00009##

    [0267] When the ester-containing substrate is a monoester, the products of the process of the present invention are alcohols. When the ester-containing substrate is a lactone, the product of the process of the present invention is a diol. When the ester-containing substrate contains multiple ester moieties, the products of the process of the present invention are a polyol and alcohols. In preferred processes of the present invention, the process does not produce a hemiacetal by-product.

    [0268] In the instance the ester-containing substrate contains an alkenyl and/or an alkynyl moiety, the process of the present invention preferably selectively hydrogenates the ester moiety over the unsaturated carbon-carbon bond of the alkene and/or alkyne. Alternatively, in the instance the ester-containing substrate contains an alkenyl and/or an alkynyl moiety, the process of the present invention preferably hydrogenates both the ester moiety and the unsaturated carbon-carbon bond of the alkene and/or alkyne.

    [0269] In the instance the ester-containing substrate contains a ketone and/or an aldehyde moiety, the process of the present invention preferably hydrogenates both the ester moiety and the carbon-oxygen double bond of the ketone and/or aldehyde.

    [0270] In the instance the ester-containing substrate contains an alkenyl and/or an alkynyl moiety, and a ketone and/or an aldehyde moiety, the process of the present invention preferably selectively hydrogenates both the ester moiety and the carbon-oxygen double bond of the ketone and/or aldehyde over the unsaturated carbon-carbon bond of the alkene and/or alkyne. Alternatively, in the instance the ester-containing substrate contains an alkenyl and/or an alkynyl moiety, and a ketone and/or an aldehyde moiety, the process of the present invention preferably hydrogenates the ester moiety, the unsaturated carbon-carbon bond of the alkene and/or alkyne, and the carbon-oxygen double bond of the ketone and/or aldehyde.

    [0271] As will be understood by a skilled person, an alkoxide base is added and remains present during the hydrogenation process of the present invention. The alkoxide base can be recovered from the reaction mixture and recycled or reused in a subsequent hydrogenation process of the present invention. For example, if the ester-containing substrate is ethyl acetate and the base is sodium ethoxide, then the hydrogenation reaction will generate ethanol and return sodium ethoxide as products and the recovered sodium ethoxide can then be recycled or reused. For an alternative example, if the ester-containing substrate is ethyl decanoate and the base is sodium ethoxide, then the hydrogenation reaction will generate ethanol and decanol. In this case, the recovered and reusable alkoxide base can be sodium ethoxide and/or sodium decanoate.

    [0272] In preferred processes of the present invention, the process is a batch process. Preferably, the process is a batch process wherein any excess base is recycled or reused. The base may be recycled or reused once, twice, three times, or more.

    [0273] In preferred processes of the present invention, the process is a flow process. Preferably, the process is a flow process wherein any excess base is recycled or reused. The base may be recycled or reused once, twice, three times, or more.

    [0274] The invention will now be further described by way of the following non-limiting examples.

    Examples

    Materials

    [0275] Ru-SNS and Ru-PNN are commercially available from Johnson Matthey.

    [0276] Ru-SNN was made according to the procedure outlined in Puylaert et al., Chem. Eur. J. 2017, 23, 8473-8481.

    [0277] NaOEt and the ester-containing substrates EE1, EE2, EE3, EE5, EE6, ME1, ME2, ME6, WE1, MM, EM, ETD, ED, MO, and ethyl acetate are all commercially available, e.g. from Sigma Aldrich, Fisher Scientific, Alfa Aesar, Acros Organics etc.

    Measurement Methods

    [0278] Gas chromatography (GC) measurements were conducted using a Varian 3900 or 3800 gas chromatograph system. Unless otherwise indicated, reaction conversions were determined by GC analysis.

    [0279] Nuclear magnetic resonance (NMR) measurements were conducted using a Bruker Avance Ill 400 (400 MHz) spectrometer.

    General Procedure for Ester Hydrogenation

    [0280] To an 8 mL vial, a catalyst Ru-SNS, Ru-PNN, Ru-SNN was added, followed by solid base, NaOEt, and then 10-20 mmol of ester-containing substrate. The vial was then added to a Biotage Endeavor screening system, before the stirring head was sealed and the reaction mixture purged with nitrogen. A purge sequence involved pressurizing to approximately 45 psi nitrogen and then releasing the pressure (repeated 5 times). The reactor was then pressurised with hydrogen, then heated and pressurized to a set pressure of hydrogen. Once the reaction time was complete, typically 16 hrs, the reaction was allowed to cool to room temperature. Nitrogen purge cycles (5 repeats) were then carried out to remove hydrogen. The reaction mixture was then analysed via GC and NMR.

    Example 1: Ester Hydrogenation

    [0281] The General Procedure described above was carried out on the following ester-containing substrates:

    ##STR00010## ##STR00011##

    [0282] The conditions used in each reaction are listed in Tables 1a and 1b below. The results of each reaction, in terms of conversion and TON, are also listed in Tables 1a and 1b. In the instances where the substrate was EE3 and ETD, the carbon-carbon double bond was not reduced under the reaction conditions (i.e. the process was selective for reduction of the ester moiety).

    [0283] The results in Tables 1a and 1b show that the process of the present invention can achieve high conversion and industrially useful TON for the ester hydrogenation of a wide range of ester-containing substrates, including methyl esters, ethyl esters and even wax esters, at extremely low catalyst loadings (e.g. 400,000/1 S/C or lower). The results also show that a range of different transition metal catalysts containing tridentate ligands can be used to perform the hydrogenation reaction.

    [0284] Entry 1 of Table 1a further demonstrates that even at hydrogen pressures of as low as 5 bar, efficient turnover (TON=48650) and conversion (97.3%) can still be achieved at very low catalyst loadings (50,000/1 S/C, EE1/Ru-PNN).

    [0285] Entry 3 of Table 1a further shows that an economical ester hydrogenation process can be achieved at an extremely low catalyst loading (400,000/1 S/C, EE1/Ru-SNS), as a very high TON of 324000 was achieved. The reaction proceeded with an 81.0% conversion, which is thought to be due to the trade-off between catalyst activity and conversion that occurs at very low catalyst loadings. With such a high TON value, the partial conversion is not an issue as the starting materials and products are easily separable. The recovered starting material can then be re-subjected to the ester hydrogenation process of the present invention.

    [0286] Entries 5 and 6 of Table 1b further show that the use of small amounts of solvent (e.g. EtOH) is not determinantal to conversion or TON. To the contrary, the inventors have found that the use of solvent in this way can help improve reaction performance for certain types of substrate.

    Example 2a: Variation of Amount of Base

    [0287] The General Procedure described above was carried out using ethyl dodecanoate (EE2) as the ester-containing substrate and either Ru-SNS or Ru-PNN as catalyst (at a S/C loading of 100,000/1). Temperature, pressure, catalyst loading and substrate amount were kept constant, but the amount of solid NaOEt base was altered. The results are shown in Table 2a below.

    [0288] The results in Table 2a clearly show that when the amount of solid NaOEt base in the reaction mixture is increased, the conversion for the ester hydrogenation reaction increases dramatically despite the S/C catalyst loading remaining extremely low (i.e. 100,000/1). This was observed for both sets of experiments, i.e. those involving the Ru-SNS catalyst and those involving the Ru-PNN catalyst. In each set of experiments, conversion increases as the base is increased from 10 mol % up to 40 mol %. Furthermore, when the amount of base is at least 30 mol %, conversions of over 96% can be achieved. Significantly lower conversions are observed at amounts of base less than 30 mol %, e.g. at 20 mol % base a conversion of 85.7% was observed for Ru-SNS and a conversion of 59.3% was observed for Ru-PNN, whilst at 10 mol % base a conversion 53.5% was observed for Ru-SNS and a conversion of 25.4% was observed for Ru-PNN.

    Example 2b: Variation of Amount of Base

    [0289] The General Procedure described above was carried out using ethyl decanoate (ED) as the ester-containing substrate and Ru-PNN as catalyst (at a S/C loading of 100,000/1). Temperature, pressure, catalyst loading and substrate amount were kept constant, but the amount of solid NaOEt base was altered. In some experiments, the amount of base employed was greater than that employed in the experiments of Example 2a. The results are shown in Table 2b below.

    [0290] The results in Table 2b show that when the amount of solid NaOEt base in the reaction mixture is increased, the conversion for the ester hydrogenation reaction increases despite the S/C catalyst loading remaining extremely low (i.e. 100,000/1). In these experiments, conversion increased as the base increased from 30 mol % up to 50 mol %.

    Example 2c: Variation of Amount of Base

    [0291] The General Procedure described above was carried out using ethyl decanoate (ED) as the ester-containing substrate and either Ru-SNS or Ru-PNN as catalyst (at a S/C loading of 50,000/1). Temperature, pressure, catalyst loading and substrate amount were kept constant, but the amount of solid NaOEt base was altered. The results are shown in Table 2c below.

    [0292] Compared to the experiments described in Examples 2a and 2b, the experiments of Example 2c were conducted at a lower hydrogen pressure of 12 bar. This means that the effect of the change in the amount of base is more pronounced as the reaction is limited by the lower hydrogen concentration. The results in Table 2c show that higher activity was observed in reactions using more base: for both Ru-SNS and Ru-PNN, conversion gradually increased as the amount of base used also increased. Turnover frequency (TOF) was found to follow a similar pattern to reaction conversion, with values for the Ru-PNN-catalysed reactions being higher than those catalysed by Ru-SNS suggesting Ru-PNN is a more active catalyst at lower hydrogen pressure. Example 2c therefore shows that using higher amounts of base can improve catalytic activity and conversion at low hydrogen pressure.

    Example 3a: Variation of Temperature

    [0293] The General Procedure described above was carried out using ethyl benzoate (EE1) as the ester-containing substrate and Ru-SNS as catalyst (at a S/C loading of either 50,000/1 or 100,000/1). Pressure and the amount of base were kept constant, but the temperature at which the reaction was conducted was altered. The results are shown in Table 3 below.

    [0294] As a first point, it is clear that a catalyst is required to bring about the hydrogenation of this ester-containing substrate as 0% conversion was observed when no catalyst was employed (entry 1).

    [0295] Entries 2 and 3 are repeats of the same experiment wherein the following conditions were used: 50,000/1 catalyst loading, 30 bar hydrogen pressure, 50 mol % NaOEt base, 20 mmol substrate, and 40° C. temperature. High conversions were observed for the hydrogenation reaction (99.0% and 99.2%, respectively). When the experiment was repeated using a higher temperature of 65° C., conversion decreased significantly to 79.0% (entry 4).

    [0296] Entries 5 and 6 are repeats of the same experiment wherein the following conditions were used: 100,000/1 catalyst loading, 30 bar hydrogen pressure, 50 mol % NaOEt base, 20 mmol substrate, and 40° C. temperature. High conversions were observed for the hydrogenation reaction (99.0% and 99.4%, respectively). When the experiment was repeated using a higher temperature of 65° C., conversion decreased significantly to 82.5% (entry 7).

    [0297] The results in Table 3 show that the ester hydrogenation reaction achieves higher conversion at lower temperatures.

    Examples 3b and 3c: Variation of Temperature

    [0298] Ethyl oleate EE3 (technical grade, 70% from Alfa Aesar) was first analysed by GC for purity. The results showed that the ethyl oleate used in Examples 3b and 3c had the following composition, indicating that some side products were to be expected in the subsequent hydrogenation reactions.

    TABLE-US-00001 Compositional Structure analysis Linoleic C18:2 [00012]embedded image  9.8% Oleic C18:1 [00013]embedded image 76.7% Stearic C18:0 [00014]embedded image  4.2% Palmitic C16:0 [00015]embedded image  9.3%

    Example 3b

    [0299] The General Procedure described above was carried out using ethyl oleate (EE3) as the ester-containing substrate and Ru-SNS as catalyst. Pressure, substrate amount, and base amount were kept constant but the catalyst loading (S/C) and temperature at which the reaction was conducted was altered. The results are shown in Table 4 below.

    [0300] At a catalyst loading of 25,000/1 (S/C), the C18:1 hydrogenation reaction conversion was similar when temperatures of 40° C. and 65° C. were employed and all other conditions were kept constant. When the temperature was raised to 80° C., a significant decrease in C18:1 conversion was observed (entries 1, 4 and 7).

    [0301] At a catalyst loading of 50,000/1 (S/C), the C18:1 hydrogenation reaction conversion decreased from 100% to 93.2% when the temperature was raised from 40° C. to 65° C. and all other conditions were kept constant (entries 2 and 5).

    [0302] At a catalyst loading of 100,000/1 (S/C), the C18:1 hydrogenation reaction conversion decreased dramatically from 99.1% to 9.7% when the temperature was raised from 40° C. and 65° C. and all other conditions were kept constant (entries 3 and 6).

    [0303] The results in Table 4 show that the ester hydrogenation achieves higher C18:1 conversion at lower temperatures. Furthermore, the effect is more pronounced at lower catalyst loadings, with bigger decreases in C18:1 conversion being seen as temperature is increased.

    Example 3c

    [0304] The General Procedure described above was carried out using ethyl oleate (EE3) as the ester-containing substrate and Ru-PNN as catalyst. Pressure, substrate amount, and base amount were kept constant but the catalyst loading (S/C) and temperature at which the reaction was conducted was altered. The results are shown in Table 5 below.

    [0305] At a catalyst loading of 25,000/1 (S/C), the C18:1 hydrogenation reaction conversion was similar when temperatures of 40° C., 65° C. and 80° C. were employed and all other conditions were kept constant (entries 1, 4 and 7).

    [0306] At a catalyst loading of 100,000/1 (S/C), the C18:1 hydrogenation reaction conversion decreased dramatically from 100% to 51.6% when the temperature was raised from 40° C. to 65° C. and all other conditions were kept constant (entries 3 and 6).

    [0307] The results in Table 5 show that the ester hydrogenation achieves higher C18:1 conversion at lower temperatures. Again, the effect is more pronounced at lower catalyst loadings, with bigger decreases in C18:1 conversion being seen as temperature is increased.

    [0308] The results of Examples 3a, 3b and 3c indicate that the ester hydrogenation reaction is sensitive to temperature and performs best in terms of reaction conversion at lower temperatures (e.g. −40° C.). This has been demonstrated across a range of ester-containing substrates and catalysts. A lower reaction temperature is particularly beneficial when very low catalyst loadings are used.

    Example 3d: Variation of Temperature

    [0309] Methyl oleate (technical grade, C18′ 70-85% from ThermoFisher Scientific) was first analysed by GC for purity. The results showed that the methyl oleate used in Example 3d had the following composition, indicating that some side products were to be expected in the subsequent hydrogenation reactions.

    TABLE-US-00002 Compositional Structure analysis Linoleic C18:2 [00016]embedded image 10.8% Oleic C18:1 [00017]embedded image 81.1% Stearic C18:0 [00018]embedded image  3.3% Palmitic C16:0 [00019]embedded image  4.8%

    [0310] The General Procedure described above was carried out using methyl oleate as the ester-containing substrate and Ru-SNS as catalyst. Pressure, substrate amount, and base amount were kept constant but the catalyst loading (S/C) and temperature at which the reaction was conducted was altered. The results are shown in Table 6 below.

    [0311] At a catalyst loading of 25,000/1 (S/C), the C18:1 hydrogenation reaction conversion was similar when temperatures of 40° C., 50° C. and 60° C. were employed and all other conditions were kept constant. When the temperature was raised to 70° C., a significant decrease in C18:1 conversion was observed.

    [0312] At a catalyst loading of 50,000/1 (S/C), the C18:1 hydrogenation reaction conversion consistently decreased as the temperature was increased from 40° C. to 70° C. (in increments of 10° C.) and all other conditions were kept constant.

    [0313] The results in Table 6 show that the ester hydrogenation achieves higher C18:1 conversion at lower temperatures. Again, the effect is more pronounced at lower catalyst loadings, with bigger decreases in C18:1 conversion being seen as temperature is increased.

    Example 4: Variation of Pressure

    [0314] The ethyl oleate (EE3) sample used in Examples 3b and 3c was also employed in Example 4.

    [0315] The General Procedure described above was carried out using ethyl oleate (EE3) as the ester-containing substrate and Ru-SNS or Ru-PNN as catalyst. In this Example, the ester hydrogenation reaction was conducted at a lower hydrogen pressure of 10 bar. The results are shown in Table 7 below.

    [0316] Comparison of entry 1 of Table 7 with entry 2 of Table 4 shows comparable results. Thus, when all other variables remain constant, the ester hydrogenation reaction conducted using Ru-SNS achieves a high C18:1 conversion even at a much lower hydrogen pressure of 10 bar (compared to 30 bar in entry 2 of Table 4).

    [0317] Comparison of entry 2 of Table 7 with entry 2 of Table 5 also shows comparable results. Thus, when all other variables remain constant, the ester hydrogenation reaction conducted using Ru-PNN achieves a high C18:1 conversion even at a much lower hydrogen pressure of 10 bar (compared to 30 bar in entry 2 of Table 5).

    [0318] Being able to operate the ester hydrogenation process of the present invention at lower pressures offers the additional advantages of reduced cost and improved safety. In addition, the need for specialist equipment that must withstand high pressures is avoided.

    Example 5: Recycling/Reuse of Base

    [0319] A series of experiments was performed to determine if it is possible to recycle/reuse the base from a first run of the hydrogenation reaction in a subsequent second run.

    [0320] First Run

    [0321] The General Procedure described above was carried out using ethyl acetate as the ester-containing substrate and Ru-PNN as catalyst (at a S/C loading of 50,000/1). The reaction was repeated three times using the conditions shown in Table 8a below.

    [0322] Second Run

    [0323] The ethanol product of the hydrogenation reaction was removed under vacuum from each of the reaction mixtures of the first run. The base recovered from each reaction (in this case, NaOEt) was then transferred to three separate vials for a second run. The vials were then prepared as follows:

    Test (i), using reaction mixture of experiment 1 of Table 8a—addition of fresh ethyl acetate substrate (2 mL, 20.47 mmol), addition of fresh Ru-PNN catalyst (0.309 mg, 4.09×10.sup.−3 mmol), and addition of fresh NaOEt base to top up to 50 mol %;
    Test (ii), using reaction mixture of experiment 2 of Table 8a—addition of fresh ethyl acetate substrate (2 mL, 20.47 mmol) and addition of fresh Ru-PNN catalyst (0.309 mg, 4.09×10.sup.−3 mmol).

    [0324] The vials were then added to a Biotage Endeavor screening system, and the hydrogenation reactions carried out according to the General Procedure described above. The results are shown in Table 8b below.

    [0325] The results show that the reaction carried out using only recycled/reused base (test (ii)) performed equally well in terms of conversion compared to the reaction topped up with fresh base (test (i)), and a similar rate of reaction was observed for both. The results indicate that the base generated in a first run of the hydrogenation reaction can be effectively recycled/reused in a second run. It is also envisaged that further recycling/reuse of the generated base could be carried out, e.g. in a third run. This has the potential to make the overall process more cost effective, especially on an industrial scale. The results also show that it is possible to top up the recycled/reused base with fresh base in order to mitigate for mechanical losses, e.g. when operating the process on a small scale.

    TABLE-US-00003 TABLE 1a H.sub.2 Loading Base Temperature pressure Conversion Entry Ester Catalyst (S/C) (mol %) (° C.) (bar) (%) TON 1 EE1 Ru-PNN 50000 50 40 5 97.3 48650 2 EE1 Ru-PNN 100000 50 40 30 96.7 96700 3 EE1 Ru-SNS 400000 50 40 30 81.0 324000 4 EE1 Ru-SNS 200000 50 40 30 98.1 196200 5 ME1 Ru-SNS 200000 50 40 30 41.2 82400 6 ME1 Ru-SNS 100000 50 40 30 87.1 87100 7 ME1 Ru-SNS 50000 50 40 30 94.2 47100 8 EE2 Ru-PNN 200000 50 40 30 78.1 156200 9 EE2 Ru-PNN 100000 40 40 30 99.9 99900 10 EE2 Ru-SNS 200000 30 40 30 11.5 23000 11 EE2 Ru-SNS 100000 40 40 30 97.4 97400 12 ME2 Ru-SNS 50000 40 40 30 10.6 5300 13 ME2 Ru-SNS 25000 40 40 30 99.2 24800 14 EE3 Ru-PNN 400000 50 40 30 32.2 128800 15 EE3 Ru-PNN 200000 50 40 30 92.5 185000 16 EE3 Ru-PNN 100000 50 40 30 97.7 97700 17 EE3 Ru-SNS 200000 50 40 30 96.4 192800 18 EE3 Ru-SNN 100000 50 40 30 92.9 92900 19 EE3 Ru-SNN 50000 50 40 30 96.2 48100 20 EE5 Ru-PNN 50000 40 40 30 77.5 38750 21 EE5 Ru-SNS 40000 40 40 30 96.4 38560 22 EE6 Ru-PNN 100000 50 65 30 25.2 25200 23 EE6 Ru-PNN 25000 50 40 30 97.3 24325 24 EE6 Ru-SNS 100000 50 40 30 19.7 19700 25 EE6 Ru-SNS 50000 50 40 30 80.1 40050 26 ME6 Ru-SNS 125000 50 40 30 60.8 76000 27 ME6 Ru-SNS 25000 50 40 30 25.0 6250 28 WE1 Ru-SNS 100000 50 40 30 96.7 96700 29 WE1 Ru-PNN 50000 50 40 30 98.6 49300 30 WE1 Ru-PNN 100000 50 40 30 97.3 97300 31 WE1 Ru-PNN 200000 50 40 30 62.5 125000

    TABLE-US-00004 TABLE 1b Hydrogen Substrate Loading Temperature Pressure Base Conversion, No. Substrate (mmol) Catalyst (S/C) (° C.) (bar) (mol %) Solvent GC (%) TON 1 MM 10 Ru-PNN 50000 40 30 50 N/A 99.3 49650 2 EM 10 Ru-SNS 100000 40 30 50 N/A 94.9 94900 3 ETD 10 Ru-SNS 72000 40 30 30 N/A 87.7 48672 4 ETD 10 Ru-SNS 50000 40 30 50 N/A 100.0 48650 5 MO 10 Ru-PNN 50000 40 30 50 N/A 99.3 49650 6 MO 10 Ru-PNN 50000 40 30 50 EtOH.sup.1 98.1 49050 7 ED 17.37 Ru-SNS 100000 40 30 50 N/A 86.8 86800 (.sup.10.1 mL of EtOH was added to the vial prior to the purging sequence)

    TABLE-US-00005 TABLE 2a Catalyst Hydrogen Substrate loading Temperature Pressure Base Conversion, Catalyst No. (mmol) (S/C) (° C.) (bar) (mol %) GC (%) Ru-SNS 1 20 100,000/1 40 30 10 53.5 2 20 100,000/1 40 30 20 85.7 3 20 100,000/1 40 30 30 96.8 4 20 100,000/1 40 30 40 99.9 Ru-PNN 5 20 100,000/1 40 30 10 25.4 6 20 100,000/1 40 30 20 59.3 7 20 100,000/1 40 30 30 97.0 8 20 100,000/1 40 30 40 99.9 (substrate: ethyl dodecanoate, EE2)

    TABLE-US-00006 TABLE 2b Catalyst Hydrogen Substrate loading Temperature Pressure Base Conversion, Catalyst No. (mmol) (S/C) (° C.) (bar) (mol %) GC (%) Ru-PNN 1 17.37 100,000/1 40 30 30 70.5 2 17.37 100,000/1 40 30 40 83.4 3 17.37 100,000/1 40 30 50 92.2 (substrate: ethyl decanoate, ED)

    TABLE-US-00007 TABLE 2c Catalyst Hydrogen Substrate loading Temperature Pressure Base Conversion, Catalyst No. (mmol) (S/C) (° C.) (bar) (mol %) GC (%) Ru-SNS 1 17.37 50,000/1 40 12 30 67.1 2 17.37 50,000/1 40 12 40 74.7 3 17.37 50,000/1 40 12 50 91.2 Ru-PNN 6 17.37 50,000/1 40 12 30 73.9 7 17.37 50,000/1 40 12 40 81.2 8 17.37 50,000/1 40 12 50 88.4 9 17.37 50,000/1 40 12 60 94.1 10 17.37 50,000/1 40 12 70 95.7 (substrate: ethyl decanoate, ED)

    TABLE-US-00008 TABLE 3 Catalyst Hydrogen Substrate loading Temperature Pressure mol % Conversion, Catalyst No. (mmol) (S/C) (° C.) (bar) base GC (%) Ru-SNS 1 20 0 40 30 50 0 2 20  50000/1 40 30 50 99.0 3 20  50000/1 40 30 50 99.2 4 20  50000/1 65 30 50 79.0 5 20 100000/1 40 30 50 99.0 6 20 100000/1 40 30 50 99.4 7 20 100000/1 65 30 50 82.5 (substrate: ethyl benzoate, EE1)

    TABLE-US-00009 TABLE 4 Catalyst Hydrogen Substrate Loading Temperature Pressure Base C18:1 Catalyst No. (mmol) (S/C) (° C.) (bar) mol % C16:0 C18:0 C18:1 C18:2 Conversion Ru-SNS 1 10 25,000/1 40 30 50 10.1 3.6 73.9 8.1 97.7 2 10 50,000/1 40 30 50 10.8 3 75.9 8.2 100.0 3 10 100,000/1  40 30 50 10.2 3.6 75 7.4 99.1 4 10 25,000/1 65 30 50 10.6 3.6 74.4 7.8 98.3 5 10 50,000/1 65 30 50 8.4 3.1 70.5 6.9 93.2 6 10 100,000/1  65 30 50 0 0 7.31 0.96 9.7 7 10 25,000/1 80 30 50 5.3 0.85 35.7 3.2 47.2 (substrate: ethyl oleate, EE3)

    TABLE-US-00010 TABLE 5 Catalyst Hydrogen Substrate Loading Temperature Pressure Base C18:1 Catalyst No. (mmol) (S/C) (° C.) (bar) mol % C16:0 C18:0 C18:1 C18:2 Conversion Ru-PNN 1 10 25,000/1 40 30 50 9.6 3.8 73.7 8.3 97.4 2 10 50,000/1 40 30 50 10.6 3.6 74.3 8.1 98.2 3 10 100,000/1  40 30 50 9.8 3.5 76.1 8.3 100.0 4 10 25,000/1 65 30 50 10.8 3.6 74.6 7.7 98.6 5 10 50,000/1 65 30 50 10.6 3.9 73.8 7.8 97.6 6 10 100,000/1  65 30 50 4.5 0.6 39 4.7 51.6 7 10 25,000/1 80 30 50 9.7 4 73.9 7.5 97.7 (substrate: ethyl oleate, EE3)

    TABLE-US-00011 TABLE 6 Catalyst Hydrogen C18:1 Substrate Loading Temperature Pressure Base conversion Catalyst No. (mmol) (S/C) (° C.) (bar) mol % C16:0 C18:0 C18:1 C18:2 to alcohol Ru-SNS 1 11.79 25,000/1 40 30 50 4.7 4.0 80.7 10.6 99.5 2 11.79 25,000/1 50 30 50 3.9 3.2 79.7 9.5 98.3 3 11.79 25,000/1 60 30 50 4.0 3.2 79.4 9.1 97.9 4 11.79 25,000/1 70 30 50 3.3 4.2 56.8 7.2 70.0 5 11.79 50,000/1 40 30 50 3.6 3.0 82.6 10.8 100.0 6 11.79 50,000/1 50 30 50 4.6 4.3 71.5 9.8 88.2 7 11.79 50,000/1 60 30 50 2.5 2.8 45.6 5.4 56.2 8 11.79 50,000/1 70 30 50 1.4 1.7 31.8 4.0 39.2 (substrate: methyl oleate; reaction duration = 64 h)

    TABLE-US-00012 TABLE 7 Catalyst Hydrogen Starting Substrate Loading Temperature Pressure Base Material C18:1 No. Catalyst (mmol) (S/C) (° C.) (bar) mol % C16:0 C18:0 C18:1 C18:2 (%) Conversion 1 Ru-SNS 10 50,000/1 40 10 50 6.7 0 72.4 7.4 1.9 97.4 2 Ru-PNN 10 50,000/1 40 10 50 10 0.4 66.4 9.2 3.7 94.7 (substrate: ethyl oleate, EE3)

    TABLE-US-00013 TABLE 8a Catalyst Hydrogen Conversion, Substrate loading Temperature Pressure Base .sup.1H NMR.sup.a Catalyst No. (mmol) (S/C) (° C.) (bar) (mol %) (%) Ru-PNN 1 20.47 50,000/1 40 30 50 97.3 2 20.47 50,000/1 40 30 50 98.7 3 20.47 50,000/1 40 30 50 92.2 (substrate: ethyl acetate - first run); .sup.aConversion calculated from integrals of corresponding product and starting material peaks in the .sup.1H NMR spectra.

    TABLE-US-00014 TABLE 8b Catalyst Hydrogen Base Conversion, Substrate loading Temperature Pressure recovered Base .sup.1H NMR.sup.a Catalyst Test (mmol) (S/C).sup.b (° C.) (bar) (%) (mol %) (%) Ru-PNN i 20.47 50,000/1 40 30 82.5 50 92.8 ii 20.47 50,000/1 40 30 85.8 44 95.0 (substrate: ethyl acetate - second run); .sup.aConversion calculated from integrals of corresponding product and starting material peaks in the .sup.1H NMR spectra; .sup.bS/C calculated based upon amount of fresh substrate added prior to second run.