NEW PROCESS FOR CATALYTIC PREPARATION OF OXALATE AND OXAMIDE COMPOUNDS

Abstract

An M-NHC catalyst, in which M represents Pd or Pt and NHC represents an N-heterocyclic carbene group, including at least one M atom linked to at least one N-heterocyclic carbene ligand, and the method of using the M-NHC catalyst for selectively preparing oxalates or oxamides, from carbon monoxide, an oxidant, in particular molecular oxygen or air, and an alcohol or an amine respectively, optionally in the presence of a promoter.

Claims

1-17. (canceled)

18. A method for selectively preparing an oxalate compound or an oxamide compound comprising: a step A of contacting an alcohol or an amine, respectively, with: carbon monoxide, in particular used from 1.0 to 10.0 MPa, in particular 6.5 MPa, an oxidant, in particular oxygen or air, preferably oxygen used at 0.5 to 2.5 MPa, an M-NHC catalyst, wherein M represents Pd or Pt and NHC represents an N-heterocyclic carbene group, comprising at least one M atom linked to at least one N-heterocyclic carbene ligand, optionally a promoter, optionally a base, optionally a solvent, to obtain a reaction medium, to obtain the oxalate compound or the oxamide compound.

19. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 18, comprising: a step A of contacting an alcohol or an amine, respectively, with a promoter.

20. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 18, comprising: a step A of contacting an alcohol or an amine, respectively, with a base.

21. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 18, comprising: a step A of contacting an alcohol or an amine, respectively, with a solvent.

22. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 18, comprising a step B of heating the reaction medium.

23. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 19, wherein the promoter is selected from: tetrabutylammonium iodide (Bu.sub.4NI), sodium iodide (NaI) and potassium iodide (KI), preferably tetrabutylammonium iodide.

24. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 20, wherein the base is selected from potassium carbonate (K.sub.2CO.sub.3), sodium carbonate (Na.sub.2CO.sub.3), potassium tert-butylate (KotBu), potassium phosphate (K.sub.3PO.sub.4) and triethylamine (Et.sub.3N).

25. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 21, wherein the solvent is selected from acetonitrile, toluene, 1,4-dioxane, tetrahydrofuran, ethanol, methanol and ethyl acetate, preferably acetonitrile and tetrahydrofuran.

26. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 18, wherein the catalyst corresponds to Formula II: ##STR00071## wherein: R.sub.1 and R.sub.2 independently of one another represent a group chosen from: C.sub.1 to C.sub.10 linear or branched alkyl C.sub.3 to C.sub.10 cycloalkyl C.sub.6 to C.sub.20 aryl or C.sub.3 to C.sub.20 heteroaryl, and C.sub.7 to C.sub.20 alkyl-aryl or C.sub.4 to C.sub.20 alkyl-heteroaryl, L.sub.1 represents a halogen atom chosen from Cl, Br and I, and or L.sub.2 and L.sub.3 represent a bidentate ligand, in particular chosen from acetylacetonate (acac), allyl, cinnamyl and acetate, preferably acetylacetonate, or L.sub.2 represents a halogen atom chosen from Cl, Br and I, and L.sub.3 represents a monodentate ligand, in particular selected from: pyridine, 3-chloropyridine, acetonitrile, triethylamine, or a phosphine-based ligand, in particular triphenylphosphine, preferably 3-chloropyridine, said compound of Formula II can be bonded to a support, in particular a polymer or silica, by at least one of the groups R.sub.1 or R.sub.2.

27. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 26, wherein the catalyst corresponds to Formula II, wherein: L.sub.1 represents an iodine atom, and or L.sub.2 and L.sub.3 are linked and together represent a bidentate ligand, or L.sub.2 represents a halogen atom chosen from Cl, Br and I and L.sub.3 represents a monodentate ligand.

28. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 26, wherein the catalyst corresponds to Formula II, wherein: L.sub.1 and either L.sub.2 each represent an iodine atom and L.sub.3 represents a monodentate ligand

29. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 18, wherein the catalyst corresponds to Formula III: ##STR00072## wherein: R.sub.1, R.sub.2, R.sub.3 and R.sub.4 independently of one another represent a group selected from: C.sub.1 to C.sub.10 linear or branched alkyl C.sub.3 to C.sub.10 cycloalkyl C.sub.6 to C.sub.20 aryl or C.sub.3 to C.sub.20 heteroaryl, and C.sub.7 to C.sub.20 alkyl-aryl or C.sub.4 to C.sub.20 alkyl-heteroaryl, or L.sub.1 and L.sub.2 represent each other independently: a halogen atom selected from Cl, Br and I, or a monodentate ligand, or L.sub.1 and L.sub.2 are linked and represent a bidentate ligand, said compound of Formula II can be bonded to a support in particular a polymer or silica, by at least one of the groups R.sub.1, R.sub.2, R.sub.3 or R.sub.4, optionally one of the groups R.sub.1 or R.sub.2 can be linked to R.sub.3 or R.sub.4 and together represent a bidentate group comprising two N-heterocyclic carbene groups.

30. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 29, wherein the catalyst corresponds to Formula III, wherein at least one of the groups L.sub.1 and L.sub.2 represents an iodine atom, or wherein the groups L.sub.1 and L.sub.2 each represent an iodine atom.

31. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 18, wherein the catalyst corresponds to Formula IV: ##STR00073## wherein: R.sub.1 and R.sub.2 independently of one another represent a group chosen from: C.sub.1 to C.sub.10 linear or branched alkyl C.sub.3 to C.sub.10 cycloalkyl C.sub.6 to C.sub.20 aryl or C.sub.3 to C.sub.20 heteroaryl, and C.sub.7 to C.sub.20 alkyl-aryl or C.sub.4 to C.sub.20 alkyl-heteroaryl, L.sub.1 and L.sub.2 represent a halogen atom chosen from Cl, Br and I.

32. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 26, wherein the catalyst corresponds to Formula II-1 or Formula II-2 or Formula II-3: ##STR00074## wherein: R.sub.1 and R.sub.2 independently of one another represent a group chosen from: C.sub.1 to C.sub.10 linear or branched alkyl C.sub.3 to C.sub.10 cycloalkyl C.sub.6 to C.sub.20 aryl or C.sub.3 to C.sub.20 heteroaryl, and C.sub.7 to C.sub.20 alkyl-aryl or C.sub.4 to C.sub.20 alkyl-heteroaryl, said catalyst can be bonded to a support, in particular a polymer or silica, by at least one of the groups R.sub.1 or R.sub.2, in particular said catalyst is selected from: ##STR00075## or wherein the catalyst, bound to a support (PS), is chosen from: ##STR00076##

33. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 29, wherein the catalyst corresponds to Formula III-1 ##STR00077## wherein: R.sub.1, R.sub.2, R.sub.3 and R.sub.4 independently of one another represent a group selected from: C.sub.1 to C.sub.10 linear or branched alkyl C.sub.3 to C.sub.10 cycloalkyl C.sub.6 to C.sub.20 aryl or C.sub.3 to C.sub.20 heteroaryl, and C.sub.7 to C.sub.20 alkyl-aryl or C.sub.4 to C.sub.20 alkyl-heteroaryl, said compound of Formula III-1 can be bonded to a support, in particular a polymer or silica, by at least one of the groups R.sub.1, R.sub.2, R.sub.3 or R.sub.4, optionally one of the groups R.sub.1 or R.sub.2 can be linked to R.sub.3 or R.sub.4 and together represent a bidentate group comprising two N-heterocyclic carbene groups, in particular said supported catalyst of Formula III-1 is selected from ##STR00078##

34. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 18, wherein an oxalate compound is selectively prepared and the method comprises: a step A of contacting an alcohol with carbon monoxide, oxygen or air, a PdNHC catalyst, and optionally a promoter, optionally a base, optionally a solvent, to obtain a reaction medium, a step B of heating said reaction medium to obtain the oxalate compound, in particular at a temperature of from 25 to 200 C., in particular from 60 to 110 C., preferably about 90 C.

35. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 18, wherein an oxalate compound of Formula 2 is selectively prepared, and wherein step A comprises contacting an alcohol of Formula 1 ##STR00079## wherein R.sub.a represents a group chosen from: C.sub.1 to C.sub.10 linear or branched alkyl C.sub.3 to C.sub.10 cycloalkyl in particular the alcohol is chosen from methanol, ethanol and isopropanol.

36. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 18, wherein an oxamide compound is selectively prepared, and wherein the method comprises: a step A of contacting an amine with: carbon monoxide, oxygen or air, optionally a promoter, a PdNHC type catalyst, a solvent, and optionally a base, in particular selected from K.sub.2CO.sub.3 or Et.sub.3N, to obtain a reaction medium comprising the oxamide.

37. The method for selectively preparing an oxalate compound or an oxamide compound according to claim 18, wherein an oxamide compound of Formula 4 is selectively prepared, and wherein step A comprises contacting an amine of Formula 3: ##STR00080## wherein R.sub.b and R.sub.c independently of one another represent: a hydrogen atom, C.sub.1 to C.sub.20 linear or branched alkyl group C.sub.2 to C.sub.20 linear or branched alkenyl group C.sub.1 to C.sub.20 linear or branched heteroalkyl group, the heteroatom being in particular O or N, at least one of the groups R.sub.b or R.sub.c being other than hydrogen, R.sub.b and R.sub.c can form a cycle, in particular the amine is chosen from: diethylamine, piperidine, pyrrolidine and morpholine.

Description

EXAMPLES

Example 1: Catalysts

##STR00045##

[0954] The PEPPSIIPr catalyst can be commercially obtained from Sigma Aldrich.

[0955] The [(IPr)Pd(acac)Cl], [(IMes)Pd(acac)Cl] catalysts were prepared according to the literature described in N. Marion et al (Adv. Synth. Catal. 2007, 349, 2380-2384).

[0956] The polymeric support loaded with 1-(mesityl)imidazolium (PS-IMes-HCl), was prepared according to the literature described in D.-H. Lee, et al. (Org. Lett. 2008, 10, 1609-1612).

[0957] The amount of imidazolium on the imidazolium-loaded polymer support (PS-IMes-HCl) was determined by evaluating the N content by elemental analysis (N 0.89%, i.e. a catalyst amount of: 0.32 mmol/g).

[0958] The (PS-IMes-HCl) support is used for the preparation of the [(PS-IMes)Pd(acac)Cl] catalyst described in example 2.

Example 2Preparation of [(PS-IMes)Pd(acac)Cl] Catalyst

[0959] In a flask fitted with a magnetic bar and a condenser, Pd(acac).sub.2 (456 mg, 1.5 mmol), an imidazolium-loaded polymer support (PS-IMes-HCl) (2 g, 0.32 mmol/g) and 1,4-dioxane (30 ml) were introduced and the reaction mixture formed was heated at 100 C. for 16 hr. The reaction mixture was then cooled to room temperature, filtered and the polymer support was washed vigorously with distilled water (510 ml), methanol (510 ml) and dried under reduced pressure to give [(PS-IMes) Pd(acac)Cl] (2.1 g).

[0960] The amount of Pd loaded onto the polymer support was determined using ICP-AES analysis. The polymer-supported palladium-N-heterocyclic complex (50 mg) was treated with a mixture (25 ml) of hydrochloric acid and nitric acid (1:1, v/v) at room temperature for 30 min. The orange solution formed was filtered and washed with distilled water. The filtrate and wash solution were combined to determine the amount of Pd by inductively coupled plasma atomic emission spectrometry (ICP-AES). The amount of Pd was calculated to be 0.29 mmol/g of support.

Example 3: Representative Procedure for Comparative Tests with Pd-Phosphine Catalysts

Test A:

[0961] In a general procedure, a 450 ml Parr autoclave equipped with a stirring bar was charged with palladium (II) acetylacetonate (91.3 mg, 0.3 mmol), triphenylphosphine (236.1 mg, 0.9 mmol), tetrabutylammonium iodide (0.5 g, 1.5 mmol), triethylamine (0.2 ml, 1.5 mmol), acetonitrile (100 ml) and absolute ethanol (50 ml). The reactor was sealed and the mixture purged three times with nitrogen (5 bars), then twice with oxygen (5 bars). The autoclave was then pressurised with 15 bars of oxygen and then 65 bars of carbon monoxide to give a total pressure of 80 bars; and the reaction medium was stirred at 90 C. for 14 h. The autoclave was then allowed to cool to room temperature before being slowly depressurised and purged three times with nitrogen (5 bar). The contents of the reactor were transferred to a round-bottomed flask and the excess ethanol and solvent were removed using a rotary evaporator and the diethyl oxalate DEO (9.3 g) was recovered by vacuum distillation (boiling point=120 C./30-15 mbars).

[0962] For reactions with alcohols, the results are given in terms of the mass of oxalate product obtained and described in terms of the number of NCC catalytic cycles as defined above.

Test B

[0963] Test B was carried out under the same operating conditions as Test A, but in the absence of tetrabutylammonium iodide. Traces of diethyl oxalate were observed by quantitative analysis using gas chromatography.

Test C

[0964] Test C was carried out under the same operating conditions as Test A, but in the absence of triethylamine. Traces of diethyl oxalate were observed by quantitative analysis using gas chromatography.

[0965] Table 1 shows the operating conditions and results (mass of oxalate and NCC obtained) for tests carried out with a palladium-phosphine catalyst.

TABLE-US-00001 TABLE 1 Operating conditions for tests carried out with a palladium-phosphine catalyst and yield results (mass of oxalate and NCC obtained) n m (EtOH), [Pd]cat, nBu.sub.4NI, base, solvent, O.sub.2/CO, T, Time, (DEO) Ex mmol mol % mol % mol % ml bar C. h g NCC A 856 Pd(acac).sub.2:PPh.sub.3 = 0.18 NEt.sub.3, CH.sub.3CN, 15/65 90 14 9.3 212 1:30.04 0.18 100 B 856 Pd(acac).sub.2:PPh.sub.3 = NEt.sub.3, CH.sub.3CN, 15/65 90 14 traces 1:30.04 0.18 100 C 856 Pd(acac).sub.2:PPh.sub.3 = 0.18 CH.sub.3CN, 15/65 90 14 traces 1:30.04 100

Example 4: Representative Procedure for the Catalytic Oxidative Carbonylation of Aliphatic Alcohols to Oxalates Using Homogeneous Palladium Catalysts

[0966] In a general procedure, a 450 ml Parr autoclave fitted with a stirring bar was charged with homogeneous PdNHC complex (0.3 mmol), tetrabutylammonium iodide (0.5 g, 1.5 mmol), triethylamine (0.2 ml, 1.5 mmol), acetonitrile (100 ml) and aliphatic alcohol (50 ml). The reactor was sealed and the mixture purged three times with nitrogen (5 bars), then twice with oxygen (5 bars). The autoclave was then pressurised with 15 bars of oxygen followed by 65 bars of carbon monoxide to bring the total pressure to 80 bars, and the reaction mixture was stirred at 90 C. for 14 h. The autoclave was then allowed to cool to room temperature before being slowly depressurised and purged three times with nitrogen (5 bars). The contents of the reactor were transferred to a round-bottomed flask and the excess aliphatic alcohol and solvent were removed using a rotary evaporator and the dialkyl oxalate (DEO) was recovered by vacuum distillation (boiling point=120 C./50-15 mbars). The reported dialkyl oxalate yield was calculated on the isolated yield by mass and a Catalytic Cycle Number NCC was calculated as defined above.

[0967] Table 2 shows the operating conditions and the results (mass of oxalate and NCC obtained) of the tests carried out with a homogeneous PdNHC catalyst according to the invention.

TABLE-US-00002 TABLE 2 Operating conditions for the tests carried out with a homogeneous Pd-NHC catalyst and the results for yield (mass of oxalate obtained) and NCC. n base, m (EtOH), [Pd]cat, nBu.sub.4NI, mol solvent, O.sub.2/CO, T, time, (DEO) Ex mmol mol % mol % % ml bar C. h g NCC 1 856 [00046] 0.18 NEt.sub.3, 0.18 CH.sub.3CN, 100 15/65 90 14 8 182 0.04 2 856 [00047] 0.18 NEt.sub.3, 0.18 CH.sub.3CN, 100 15/65 90 14 10 228 0.04 3 856 [00048] 0.18 NEt.sub.3, 0.18 CH.sub.3CN, 100 15/65 90 14 9.5 216 0.04

Example 5: Influence of Promoter and Base on the Oxidative Carbonylation Reaction of an Alcohol

[0968] Test A1presence of water: Test A1 is carried out under the same operating conditions as test 1 in example 4 but in the presence of water (1 mol %). The reaction yield is equivalent to test 1 in example 4.

[0969] Test A2without base And.sub.3 N: Test A2 is carried out under the same operating conditions as test 1 in example 4 but in the absence of triethylamine. Diethyl oxalate was obtained in an amount of less than 1 g.

[0970] Test A3without nBu.sub.4 NI: Test A3 was carried out under the same operating conditions as test 1 in example 4 but in the absence of tetrabutylammonium iodide. Traces of diethyl oxalate were observed (less than 0.1 g).

[0971] Table 3 shows the operating conditions and results (mass of oxalate obtained and NCC) of the tests carried out.

TABLE-US-00003 TABLE 3 shows the operating conditions for the tests carried out with Pd-NHC and the results for yield (mass of oxalate obtained) and NCC. n Et.sub.3N, O.sub.2/ m (EtOH), [Pd]cat, nBu.sub.4NI, mol CH.sub.3CN, CO, T, Time, (DEO), # mmol mol % mol % % ml Bar C. h g NCC 1 856 [00049] 0.18 0.18 100 15/65 90 14 8 182 0.04 A1 856 [00050] 0.18 0.18 100 et H.sub.2O (1 mol %) 15/65 90 14 7.8 178 0.04 A2 856 [00051] 0.18 100 15/65 90 14 <1.0 0.04 A3 856 [00052] 0.18 100 15/65 90 14 <0.1 0.04

Example 6: Representative Procedure for the Catalytic Oxidative Carbonylation of Aliphatic Alcohols to Oxalates Using a Heterogeneous PdNHC Catalyst According to the Invention

[0972] In a general procedure, a 450 ml Parr autoclave fitted with a stirring bar was charged with heterogeneous PdNHC complex (1.2 g, 0.29 mmol Pd/g, 0.35 mmol Pd), tetrabutylammonium iodide (0.5 g, 1.5 mmol), triethylamine (0.2 ml, 1.5 mmol), acetonitrile (100 ml) and aliphatic alcohol (50 ml). The reactor was sealed and the reaction mixture was purged three times with nitrogen (5 bars), then twice with oxygen (5 bars). The autoclave was then pressurised with 15 bar of oxygen and then 65 bar of carbon monoxide to bring the total pressure to 80 bar; and the reaction mixture was stirred at 90 C. for 14 h. The autoclave was then allowed to cool to room temperature before being slowly depressurised and purged three times with nitrogen (5 bar). The contents of the reactor were filtered to recover the catalyst. The filtrate was transferred to a round-bottomed flask and the excess aliphatic alcohol and solvent were removed using a rotary evaporator and the dialkyl oxalate was recovered by vacuum distillation (boiling point=120 C./50-15 mbars).

[0973] The reported dialkyl oxalate yield was calculated on the isolated yield by mass and a Catalytic Cycle Number NCC was calculated as defined above.

[0974] Table 4 shows the operating conditions and the results (mass of oxalate and NCC obtained) of a test carried out with a heterogeneous PdNHC catalyst according to the invention.

TABLE-US-00004 TABLE 4 Operating conditions for the test with the [(PS-IMes)Pd(acac)Cl] catalyst and yield results (mass of oxalate obtained) and NCC. n base, O.sub.2/ m (EtOH), nBu.sub.4NI, mol solvent, CO, T, Time, (DEO) # mmol [Pd]cat, mol % mol % % ml bar C. h g NCC 4 856 [00053] 0.18 NEt.sub.3, 0.18 CH.sub.3CN, 100 15/65 90 14 8 182 0.04

Example 7: Representative Procedure for the Recyclability Study of the [(PS-IMes)Pd(Acac)Cl] Complex

[0975] The reaction was carried out as mentioned in Example 6 above in a typical experimental procedure. However, once the reaction was complete, vented and purged with nitrogen, the catalyst was filtered and washed vigorously with distilled water (510 ml) and methanol (510 ml) to remove any traces of product or reagents present. The filtered catalyst was then dried under reduced pressure before further recycling. The dried catalyst was then used in a catalyst recyclability experiment, and it was found that the recovered catalyst could be reused for at least five consecutive cycles giving a good to appreciable yield of the desired product.

[0976] The recyclability study shows that the heterogeneous catalyst can be used in a continuous flow reactor.

[0977] Table 5 shows the conditions and results of the recyclability tests on the [(PS-IMes)Pd(acac)Cl]complex.

TABLE-US-00005 TABLE 5 Recyclability test conditions for the [(PS-IMes)Pd(acac)Cl] complex and performance results. m Cycle n[Pd], (DEO), NCC exp N mmol Carbonylation conditions g NCC total C1 1 0.3 [00054] 8 182 1096 C2 2 0.24 856 mmol (50 mL) EtOH; 1.5 mmol NEt.sub.3; 6 171 C3 3 0.198 1.5 mmol nBu.sub.4NI; CH.sub.3CN 100 mL; 6 207 C4 4 0.15 CO/O.sub.2 = 65/15, 90 C., 14h 6 274 C5 5 0.1125 4.3 262

[0978] The results of these manual recycling experiments show that the PdNHC catalyst is stable. The recovered catalyst is not, or only slightly, sensitive to water and oxygen. In addition, there is no loss of efficiency in terms of NCC during the recycling of the catalyst as part of several successive catalytic reactions.

[0979] By switching to flow-through, manual recycling is no longer necessary, preventing catalyst loss during washings, so efficiency should be maintained during the reaction as reaction conditions will be stable.

Oxamide

Example 8: Representative Procedure for the Catalytic Oxidative Carbonylation of Amines to Oxamides

[0980] PEPPSIIPr, tetrabutylammonium iodide, base, solvent and piperidine were introduced into a 450 ml Parr autoclave fitted with a stir bar. The reactor was sealed, the mixture purged three times with nitrogen (5 bar) and then twice with oxygen (5 bars). The autoclave was then pressurised with 10 bar of oxygen, followed by 65 bars of carbon monoxide to give a total pressure of 75 bar, and the reaction medium was stirred at room temperature for 18 hours. The pressure was then carefully released and the autoclave was purged three times with nitrogen (5 bar). The contents of the reactor were transferred to a round-bottomed flask and the volatile substances were removed under reduced pressure. The residue was then extracted in toluene, filtered over silica gel (2-3 cm) and the solution evaporated to dryness to give 1, 1-oxalyl dipiperidine in the form of an off-white powder.

[0981] The oxamide yield is given by mass of isolated product and a Catalytic Cycle Number (CCN) has been calculated as defined above.

Example 9: Influence of Solvent on the Catalytic Oxidative Carbonylation of Amine to Oxamide

M1-THF Test

[0982] Into a 450 ml Parr autoclave fitted with a stirring bar were introduced PEPPSI_JPr Catalyst (62.5 mg, 0.092 mmol), tetrabutylammonium iodide (2.12 g, 5.75 mmol), potassium carbonate (1.59 g, 11.5 mmol), THF (200 ml) and piperidine (22.7 ml, 230 mmol). The reactor was sealed and the mixture purged three times with nitrogen (5 bars), then twice with oxygen (5 bar). The autoclave was then pressurised with 10 bar of oxygen and then 65 bar of carbon monoxide to give a total pressure of 75 bar; and the reaction medium was stirred at room temperature for 18 h. After this time, the pressure was carefully released and the autoclave was purged three times with nitrogen (5 bar). The contents of the reactor were transferred to a round-bottomed flask and the volatile substances were removed under reduced pressure. The residue was then extracted in toluene, filtered over silica gel (2-3 cm) and the solution evaporated to dryness to give 1, 1-oxalyl dipiperidine as an off-white powder (9.5 g; 42 mmol).

Test M2Acetonitrile

[0983] Test M2 was carried out under the same conditions as test M1, except that 200 mL of acetonitrile was used instead of THF.

[0984] Result: 9.5 g of oxamide 2 were isolated.

Test M3Solvent-Free

[0985] Test M3 was carried out under the same conditions as test M1, in the absence of solvent.

[0986] Result: 4.2 g of oxamide 2 were isolated.

[0987] Table 6 shows the conditions relating to the nature and presence of the solvent and the results of catalytic oxidative carbonylation tests on amines to oxamides using homogeneous PdNHC catalysts according to the invention.

TABLE-US-00006 TABLE 6 Operating conditions with different solvents for tests with piperidine using Pd-NHC catalysts and yield results. n O.sub.2/ (piperidine), [Pd]cat, nBu.sub.4NI, base, solvent, CO, T, Time, Yield Ex mmol mol % mol % mol % ml bar C. h (oxamide) M1 230 [00055] 2.5 K2CO.sub.3 5 THF, 200 10/65 25 18 9.5 g NCC = 460 0.04 M2 230 [00056] 2.5 K2CO.sub.3 5 CH.sub.3CN, 200 10/65 25 18 9.5 g NCC = 460 0.04 M3 230 [00057] 2.5 K2CO.sub.3 5 10/65 25 18 4.2 g NCC = 203 0.04

[0988] The reaction takes place in the presence of both THE and CH.sub.3CN with the same efficiency, as demonstrated in tests M1 and M2.

[0989] The reaction takes place in the absence of solvent, as demonstrated by test M3.

Example 10: Influence of the Base on the Catalytic Oxidative Carbonylation of Amine to Oxamide

M4 Test

[0990] Test M4 was carried out under the same conditions as test M1, except that the base used was triethylamine (5 mol %).

M5 Test

[0991] Test M5 was carried out under the same conditions as test M1, with no base added.

[0992] Table 7 reports the conditions on the nature and presence of the added base and the results of catalytic oxidative carbonylation tests of amines to oxamides with homogeneous PdNHC catalysts according to the invention.

TABLE-US-00007 TABLE 7 Operating conditions with different bases for tests with piperidine using Pd-NHC catalysts and yield results. n O.sub.2/ (piperidine), [Pd]cat, nBu.sub.4NI, base, solvent, CO, T, Time, Yield # mmol mol % mol % mol % ml bar C. h (oxamide) M1 230 [00058] 2.5 K2CO.sub.3 5 THF, 200 10/65 25 18 9.5 g NCC = 460 0.04 M4 230 [00059] 2.5 NEt.sub.3 5 THF, 200 10/65 25 18 9.3 g NCC = 450 0.04 M5 230 [00060] 2.5 THF, 200 10/65 25 18 17.0 g NCC = 823 0.04

[0993] Organic and inorganic bases have comparable effects on the reaction, as demonstrated by the results of M1 and M4.

[0994] The reaction is more efficient in the absence of a base added to the reaction mixture, as demonstrated in test M5.

Example 11: Use of [(PS-IMes)Pd(Acac)Cl] Catalyst for the Catalytic Oxidative Carbonylation of Amines to Oxamides Using a Heterogeneous PdNHC Catalyst

Test M6

[0995] In a 450 ml Parr autoclave fitted with a stirring bar, [(PS-Imes)Pd(acac)Cl] catalyst (317 mg, 0.29 mmol Pd/g, 0.092 mmol Pd), tetrabutylammonium iodide (2.12 g, 5.75 mmol), THE (200 ml) and piperidine (22.7 ml, 230 mmol) were introduced. The reactor was sealed and the mixture purged three times with nitrogen (5 bars), then twice with oxygen (5 bar). The autoclave was then pressurised with 10 bars of oxygen followed by 65 bar of carbon monoxide to give a total pressure of 75 bar, and the reaction medium was stirred at room temperature for 18 hours. The pressure was then carefully released and the autoclave was purged three times with nitrogen (5 bars). The contents of the reactor were filtered to recover the catalyst. The filtrate was transferred to a round-bottomed flask and the volatiles were removed under reduced pressure. The residue was then extracted in toluene, filtered over silica gel (2-3 cm) and the solution evaporated to dryness to give 1, 1-oxalyl dipiperidine in the form of an off-white powder.

[0996] Table 8 shows the operating conditions for a test with a homogeneous catalyst and a test with a supported catalyst for the catalytic oxidative carbonylation of the amines piperidine to the oxamide 1,1-oxalyl dipiperidine, and the yield results.

TABLE-US-00008 TABLE 8 Operating conditions with a homogeneous catalyst and with a supported catalyst for oxidative carbonylation with piperidine and yield results. n base, O.sub.2/ (piperidine), nBu.sub.4NI, mol solvent, CO, T, Time, Yield Ex mmol [Pd]cat, mol % mol % % ml bar C. h (oxamide) M5 230 [00061] 2.5 THF, 200 10/65 25 18 17.0 g NCC = 823 66% 0.04 M6 230 [00062] 2.5 THF, 200 10/65 25 18 18.0 g NCC = 872 70% 0.04

Example 12: Influence of the Introduction of CO and O.SUB.2

M7 Test

[0997] Test M7 was carried out under the same conditions as test M5, except that after 18 hours of stirring at room temperature, the reactor was purged and pressurised a second time with 10 bars of oxygen and 65 bars of CO; and the reaction medium was stirred at room temperature for a further 18 hours.

[0998] Table 9 shows the operating conditions.

TABLE-US-00009 TABLE 9 Operating conditions on the influence of pressure and time conditions. n base, O.sub.2/ (piperidine), nBu.sub.4NI, mol solvent, CO, T, Time, Yield Ex mmol [Pd]cat, mol % mol % % ml bar C. H (oxamide) M5 230 [00063] 2.5 THF, 200 10/65 25 18 17.0 g NCC = 823 66% 0.04 M7 230 [00064] 2.5 THF, 200 10/65 for 18h + 10/65 for 18h 25 36 25.0 g NCC = 1211 97% 0.04

[0999] Test M7 shows that re-pressurising the reactor with additional CO and O.sub.2 during the reaction enables full yield to be achieved.

Example 13: Representative Procedure for the Catalytic Oxidative Carbonylation of Aliphatic Alcohols to Oxalates Using PtNHC Catalysts

[1000] In a general procedure, a 450 ml Parr autoclave fitted with a stirring bar is charged with homogeneous PtNHC complex (0.6 mmol), tetrabutylammonium iodide (1.1 g, 3.0 mmol), triethylamine (0.4 ml, 3.0 mmol), acetonitrile (100 ml) and aliphatic alcohol (50 ml). The reactor was sealed and the mixture purged three times with nitrogen (5 bar), then twice with oxygen (5 bar). The autoclave was then pressurised with 15 bar of oxygen and then 65 bar of carbon monoxide to bring the total pressure to 80 bar, and the reaction mixture was stirred at 90 C. for 14 hours. The autoclave was then allowed to cool to room temperature before being slowly depressurised and purged three times with nitrogen (5 bars). The contents of the reactor were transferred to a round-bottomed flask and the excess aliphatic alcohol and solvent were removed using a rotary evaporator. The dialkyl oxalate (DEO) was recovered by vacuum distillation (boiling point=120 C./50-15 mbar). The yield of dialkyl oxalate reported is calculated on the isolated yield by mass and a Catalytic Cycle Number NCC has been calculated as defined above.

Example 14: Representative Procedure for the Catalytic Oxidative Carbonylation of Amines to Oxamides Using PtNHC Catalysts

[1001] PtNHC catalyst (1.0 mmol), tetrabutylammonium iodide (2.12 g, 5.75 mmol), THE (200 ml) and piperidine (22.7 ml, 230 mmol) were added to a 450 ml Parr autoclave fitted with a stirring bar. The reactor was sealed and the mixture purged three times with nitrogen (5 bar), then twice with oxygen (5 bar). The autoclave was then pressurised with 10 bar of oxygen followed by 65 bar of carbon monoxide to give a total pressure of 75 bar, and the reaction medium was stirred at 90 C. for 14 h. The autoclave was then allowed to cool to room temperature before being slowly depressurised and purged three times with nitrogen (5 bar). The contents of the reactor were transferred to a round-bottomed flask and the volatile substances were removed under reduced pressure. The residue was then extracted in toluene, filtered through silica gel (2-3 cm) and the solution evaporated to dryness to give 1,1-oxalyl dipiperidine.

Example 15: Synthesis of a PdNHC Catalyst Supported on Silica Gel (PdCl NHC/Si.SUB.2.) of the Following Formula

##STR00065##

[1002] The catalyst was prepared in the following steps:

A) Synthesis of 1-methyl-3-(trimethoxysilylpropyl)-imidazolium chloride according to the following reaction scheme

##STR00066##

[1003] In a flask fitted with a magnetic bar and a condenser, the mixture of N-methyl imidazole (freshly distilled) (10.3160 g, 0.1258 mol) and 3-chloropropyl trimethoxysilane (25 g, 0.1258 mol) was refluxed at 95 C. for 24 hours. After cooling to room temperature, the reaction mixture was washed with diethyl ether and dried in vacuo to give the desired product.

B) Immobilisation of 1-methyl-3-(trimethoxysilylpropyl)-imidazolium chloride on the surface of silica gel according to the following reaction scheme

##STR00067##

[1004] To a solution of 1-methyl-3-(trimethoxysilylpropyl)-imidazolium chloride (0.70 g, 2.2 mmol) in toluene silica gel was added. The mixture was stirred at 105 C. for 12 hours. After cooling, the reaction mixture was filtered and washed with CH.sub.2Cl.sub.2 (3*10 mL), and dried at 60 C. in vacuo to give the silica-supported ionic liquid (2.39 g). Elemental analysis showed the presence of 0.89 mmol of ligand on 1.0 g of support.

C) Preparation of an NHCPd Complex Supported on Silica Gel According to the Following Reaction Scheme

##STR00068##

[1005] To a solution of ligand supported on silica (1.0 g, 0.89 mmol) in THE (5 mL) was added Pd(OAc).sub.2 (101 mg, 0.45 mmol). The mixture was stirred for 4 h at 60 C. and then for a further 30 min at 100 C. The NHCPd complex supported on silica was filtered through a sinter and washed with water and then with CH.sub.2Cl.sub.2 (310 mL). Once washed, the catalyst was dried.

[1006] ICP analysis showed the presence of 0.35 mmol of Pd on 1 g of support.

[1007] With a quantity of 0.35 mmol of Pd on 1 g of support, better complexation of palladium on this supported ligand is observed compared with the [(PS-IMes)Pd(acac)Cl] catalyst of example 2, which comprises a quantity of 0.29 mmol/g.

Example 16: Recyclability Study of the PdCl Catalyst NHC/Si.SUB.2

Protocol

[1008] In a general procedure, a 450 ml Parr autoclave fitted with a stirring bar was charged with heterogeneous PdNHC complex (1.0 g, 0.35 mmol Pd/g), tetrabutylammonium iodide (0.5 g, 1.5 mmol), triethylamine (0.2 ml, 1.5 mmol), acetonitrile (100 ml) and aliphatic alcohol (50 ml). The reactor was sealed and the reaction mixture purged three times with nitrogen (5 bars), then twice with oxygen (5 bar). The autoclave was then pressurised with 15 bar of oxygen followed by 65 bars of carbon monoxide to bring the total pressure to 80 bar, and the reaction mixture was stirred at 90 C. for 14 h. The autoclave was then allowed to cool to room temperature before being slowly depressurised and purged three times with nitrogen (5 bar). The contents of the reactor were filtered to recover the catalyst. The filtrate was transferred to a round-bottomed flask and the excess aliphatic alcohol and solvent were removed using a rotary evaporator and the dialkyl oxalate was recovered by vacuum distillation (boiling point=120 C./50-15 mbars). The reported dialkyl oxalate yield was calculated on the isolated yield by mass and a Catalytic Cycle Number NCC was calculated as defined above.

[1009] Table 10 shows the conditions and results of recyclability tests with the PdCl.sub.2NHC/Si catalyst.

TABLE-US-00010 TABLE 10 Recyclability test conditions with the PdCl.sub.2 NHC/Si catalyst and the yield and NCC results. n[Pd], m(DEO), NCC Exp Cycle mmol Carbonylation condition g NCC total A 1 0.35 [00069] 11 215 561 B 2 0.3 856 mmol (50 mL) EtOH; 1.5 8 182 C 3 0.25 mmol Net.sub.3; 1.5 mmol nBu.sub.4NI; 6 164 CH.sub.3CN 100 mL; CO/O.sub.2 = 65/15, 90 C., 14h

Example 17: Preparation of the Palladium Catalyst with an NHC Group Supported with Iodinated Ligands, PdI.SUB.2 .NHC/PS of the Following Formula

##STR00070##

[1010] In a flask fitted with a magnetic bar and a condenser, PdCl.sub.2 (266 mg, 1.5 mmol), an imidazolium-loaded polymeric support (PS-IMes-HCl) (1 g, 1.6 mmol/g), potassium iodide (1.2 g, 7.5 mmol), potassium carbonate (1.03 g, 7.5 mmol) and pyridine (7 ml) were introduced, potassium iodide (1.2 g, 7.5 mmol), potassium carbonate (1.03 g, 7.5 mmol) and pyridine (7 ml) were introduced and the reaction mixture formed was heated at 80 C. for 16 h. The reaction mixture was then cooled to room temperature, filtered and the polymer support was washed vigorously with distilled water (510 ml), methanol (510 ml) and dried under reduced pressure to give (1.6 g) of the desired product.

[1011] The amount of Pd loaded onto the polymer support was determined using ICP-AES analysis. The polymer-supported palladium-N-heterocyclic complex (50 mg) was treated with a mixture (25 ml) of hydrochloric acid and nitric acid (1:1, v/v) at room temperature for 30 min. The orange solution formed was filtered and washed with distilled water. The filtrate and wash solution were combined to determine the amount of Pd by inductively coupled plasma atomic emission spectrometry (ICP-AES). The amount of Pd was calculated to be 0.9 mmol/g of support.

Example 18: Carbonylation Procedure without Added Iodine Salt

[1012] The Inventors have succeeded in dispensing with the addition of iodine salt. The iodine is incorporated directly into the catalyst, such as the PdI.sub.2 NHC/PS prepared in example 17, making it possible to maintain efficient catalyst reoxidation while avoiding the need to add additional iodine salt.

Protocol

[1013] A 450 ml Parr autoclave fitted with a stirring bar was charged with heterogeneous PdNHC complex (1.0 g, 0.35 mmol Pd/g), triethylamine (0.2 ml, 1.5 mmol), acetonitrile (100 ml) and ethanol (50 ml). The reactor was sealed and the reaction mixture purged three times with nitrogen (5 bar), then twice with oxygen (5 bars). The autoclave was then pressurised with 15 bars of oxygen followed by 65 bar of carbon monoxide to bring the total pressure to 80 bar, and the reaction mixture was stirred at 90 C. for 14 h. The autoclave was cooled to room temperature before being slowly depressurised and purged three times with nitrogen (5 bars). The contents of the reactor were filtered to recover the catalyst. The filtrate was transferred to a round-bottomed flask and the residual ethanol and acetonitrile were removed using a rotary evaporator. The purified dialkyl oxalate was recovered by vacuum distillation (boiling point=120 C./50-15 mbar). The reported dialkyl oxalate yield was calculated on the isolated yield by mass and a Catalytic Cycle Number NCC was calculated as defined above.

[1014] Table 11 shows the operating conditions and the results obtained.

TABLE-US-00011 TABLE 11 Operating conditions for carbonylation using the PdI.sub.2 NHC/PS catalyst without adding an iodine salt as a promoter, and the yield and NCC results. CO O.sub.2 Time, Quantity Reaction Cat Ethanol MeCN T, ( C.) (Bar) (Bar) (h) (g) NCC 1 PdI 50 mL 100 mL 90 65 15 16 8.5 g 64 NHC/PS.sub.2 0.9 mmol (1 g)

Example 19: Representative Procedure for the Catalytic Oxidative Carbonylation of Amines to Oxamides without Added Iodine Salt

[1015] A 450 ml Parr autoclave fitted with a stirring bar was charged with the heterogeneous PdI.sub.2 NHC/PS complex prepared according to example 17 (1.0 g, 0.9 mmol Pd/g), THE (200 ml) and piperidine (22.7 ml, 230 mmol). The reactor was sealed and the mixture purged three times with nitrogen (5 bars), then twice with oxygen (5 bars). The autoclave was then pressurised with 10 bar of oxygen followed by 65 bar of carbon monoxide to give a total pressure of 75 bar, and the reaction medium was stirred at room temperature for 18 hours. The pressure was then carefully released and the autoclave was purged three times with nitrogen (5 bars). The contents of the reactor were filtered to recover the catalyst. The filtrate was transferred to a round-bottomed flask and the volatiles were removed under reduced pressure. The residue was then extracted in toluene, filtered over silica gel (2-3 cm) and the solution evaporated to dryness to give 1, 1-oxalyl dipiperidine in the form of an off-white powder.