BUTYL-BRIDGED DIPHOSPHINE LIGANDS FOR ALKOXYCARBONYLATION

Abstract

The invention relates to compounds of formula (I)

##STR00001##

where R.sup.1, R.sup.2, R.sup.3, R.sup.4 are each independently selected from —(C.sub.1-C.sub.12)-alkyl, —(C.sub.3-C.sub.12)-cycloalkyl, —(C.sub.3-C.sub.12)-heterocycloalkyl, —(C.sub.6-C.sub.20)-aryl, —(C.sub.3-C.sub.20)-heteroaryl; at least one of the R.sup.1, R.sup.2, R.sup.3, R.sup.4 radicals is a —(C.sub.3-C.sub.20)-heteroaryl radical; and R.sup.1, R.sup.2, R.sup.3, R.sup.4, if they are —(C.sub.1-C.sub.12)-alkyl, —(C.sub.3-C.sub.12)-cycloalkyl, —(C.sub.3-C.sub.12)-heterocycloalkyl, —(C.sub.6-C.sub.20)-aryl or —(C.sub.3-C.sub.20)-heteroaryl, may each independently be substituted by one or more substituents selected from —(C.sub.1-C.sub.12)-alkyl, —(C.sub.3-C.sub.12)-cycloalkyl, —(C.sub.3-C.sub.12)-heterocycloalkyl, —O—(C.sub.1-C.sub.12)-alkyl, —O—(C.sub.1-C.sub.12)-alkyl-(C.sub.6-C.sub.20)-aryl, —O—(C.sub.3-C.sub.12)-cycloalkyl, —S—(C.sub.1-C.sub.12)-alkyl, —S—(C.sub.3-C.sub.12)-cycloalkyl, —COO—(C.sub.1-C.sub.12)-alkyl, —COO—(C.sub.3-C.sub.12)-cycloalkyl, —CONH—(C.sub.1-C.sub.12)-alkyl, —CONH—(C.sub.3-C.sub.12)-cycloalkyl, —CO—(C.sub.1-C.sub.12)-alkyl, —CO—(C.sub.3-C.sub.12)-cycloalkyl, —N—[(C.sub.1-C.sub.12)-alkyl].sub.2, —(C.sub.6-C.sub.20)-aryl, —(C.sub.6-C.sub.20)-aryl-(C.sub.1-C.sub.12)-alkyl, —(C.sub.6-C.sub.20)-aryl-O—(C.sub.1-C.sub.12)-alkyl, —(C.sub.3-C.sub.20)-heteroaryl, —(C.sub.3-C.sub.20)-heteroaryl-(C.sub.1-C.sub.12)-alkyl, —(C.sub.3-C.sub.20)-heteroaryl-O—(C.sub.1-C.sub.12)-alkyl, —COOH, —OH, —SO.sub.3H, —NH.sub.2, halogen; and to the use thereof as ligands in alkoxycarbonylation.

Claims

1-8. (canceled)

9. A process comprising the following process steps: a) initially charging an ethylenically unsaturated compound; b) adding a compound of formula (I) ##STR00010## where R.sup.1, R.sup.2, R.sup.3, R.sup.4 are each independently selected from —(C.sub.1-C.sub.12)-alkyl, —(C.sub.3-C.sub.12)-cycloalkyl, —(C.sub.3-C.sub.12)-heterocycloalkyl, —(C.sub.6-C.sub.20)-aryl, —(C.sub.3-C.sub.20)-heteroaryl; at least one of the R.sup.1, R.sup.2, R.sup.3, R.sup.4 radicals is a —(C.sub.3-C.sub.20)-heteroaryl radical; and R.sup.1, R.sup.2, R.sup.3, R.sup.4, if they are —(C.sub.1-C.sub.12)-alkyl, —(C.sub.3-C.sub.12)-cycloalkyl, —(C.sub.3-C.sub.12)-heterocycloalkyl, —(C.sub.6-C.sub.20)-aryl or —(C.sub.3-C.sub.20)-heteroaryl, may each independently be substituted by one or more substituents selected from —(C.sub.1-C.sub.12)-alkyl, —(C.sub.3-C.sub.12)-cycloalkyl, —(C.sub.3-C.sub.12)-heterocycloalkyl, —O—(C.sub.1-C.sub.12)-alkyl, —O—(C.sub.1-C.sub.12)-alkyl-(C.sub.6-C.sub.20)-aryl, —O—(C.sub.3-C.sub.12)-cycloalkyl, —S—(C.sub.1-C.sub.12)-alkyl, —S—(C.sub.3-C.sub.12)-cycloalkyl, —COO—(C.sub.1-C.sub.12)-alkyl, —COO—(C.sub.3-C.sub.12)-cycloalkyl, —CONH—(C.sub.1-C.sub.12)-alkyl, —CONH—(C.sub.3-C.sub.12)-cycloalkyl, —CO—(C.sub.1-C.sub.12)-alkyl, —CO—(C.sub.3-C.sub.12)-cycloalkyl, —N—[(C.sub.1-C.sub.12)-alkyl]2, —(C.sub.6-C.sub.20)-aryl, —(C.sub.6-C.sub.20)-aryl-(C.sub.1-C.sub.12)-alkyl, —(C.sub.6-C.sub.20)-aryl-O—(C.sub.1-C.sub.12)-alkyl, —(C.sub.3-C.sub.20)-heteroaryl, —(C.sub.3-C.sub.20)-heteroaryl-(C.sub.1-C.sub.12)-alkyl, —(C.sub.3-C.sub.20)-heteroaryl-O—(C.sub.1-C.sub.12)-alkyl, —COOH, —OH, —SO.sub.3H, —NH.sub.2, halogen and a compound comprising Pd, or adding a complex comprising Pd and a compound of formula (I); c) adding an alcohol; d) feeding in CO; e) heating the reaction mixture, with conversion of the ethylenically unsaturated compound to an ester.

10. The process according to claim 9, wherein the ethylenically unsaturated compound comprises 2 to 30 carbon atoms and optionally one or more functional groups selected from carboxyl, thiocarboxyl, sulpho, sulphinyl, carboxylic anhydride, imide, carboxylic ester, sulphonic ester, carbamoyl, sulphamoyl, cyano, carbonyl, carbonothioyl, hydroxyl, sulphhydryl, amino, ether, thioether, aryl, heteroaryl or silyl groups and/or halogen substituents.

11. The process according to claim 9, wherein the ethylenically unsaturated compound is selected from ethene, propene, 1-butene, cis- and/or trans-2-butene, isobutene, 1,3-butadiene, 1-pentene, cis- and/or trans-2-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene, hexene, tetramethylethylene, heptene, 1-octene, 2-octene, di-n-butene, and mixtures thereof.

12. The process according to claim 9, wherein the ethylenically unsaturated compound comprises 6 to 22 carbon atoms.

13. The process according to claim 9, wherein the compound comprising Pd in process step b) is selected from palladium dichloride, palladium(II) acetylacetonate, palladium(II) acetate, dichloro(1,5-cyclooctadiene)palladium(II), bis(dibenzylideneacetone)palladium, bis(acetonitrile)dichloropalladium(II), palladium(cinnamyl) dichloride.

14. The process according to claim 9, wherein the alcohol in process step c) is selected from methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, tert-butanol, 3-pentanol, cyclohexanol, phenol, and mixtures thereof.

15. A process for catalysis of an alkoxycarbonylation reaction, comprising: introducing a compound of formula (I) ##STR00011## where R.sup.1, R.sup.2, R.sup.3, R.sup.4 are each independently selected from —(C.sub.1-C.sub.12)-alkyl, —(C.sub.3-C.sub.12)-cycloalkyl, —(C.sub.3-C.sub.12)-heterocycloalkyl, —(C.sub.6-C.sub.20)-aryl, —(C.sub.3-C.sub.20)-heteroaryl; at least one of the R.sup.1, R.sup.2, R.sup.3, R.sup.4 radicals is a —(C.sub.3-C.sub.20)-heteroaryl radical; and R.sup.1, R.sup.2, R.sup.3, R.sup.4, if they are —(C.sub.1-C.sub.12)-alkyl, —(C.sub.3-C.sub.12)-cycloalkyl, —(C.sub.3-C.sub.12)-heterocycloalkyl, —(C.sub.6-C.sub.20)-aryl or —(C.sub.3-C.sub.20)-heteroaryl, may each independently be substituted by one or more substituents selected from —(C.sub.1-C.sub.12)-alkyl, —(C.sub.3-C.sub.12)-cycloalkyl, —(C.sub.3-C.sub.12)-heterocycloalkyl, —O—(C.sub.1-C.sub.12)-alkyl, —O—(C.sub.1-C.sub.12)-alkyl-(C.sub.6-C.sub.20)-aryl, —O—(C.sub.3-C.sub.12)-cycloalkyl, —S—(C.sub.1-C.sub.12)-alkyl, —S—(C.sub.3-C.sub.12)-cycloalkyl, —COO—(C.sub.1-C.sub.12)-alkyl, —COO—(C.sub.3-C.sub.12)-cycloalkyl, —CONH—(C.sub.1-C.sub.12)-alkyl, —CONH—(C.sub.3-C.sub.12)-cycloalkyl, —CO—(C.sub.1-C.sub.12)-alkyl, —CO—(C.sub.3-C.sub.12)-cycloalkyl, —N—[(C.sub.1-C.sub.12)-alkyl]2, —(C.sub.6-C.sub.20)-aryl, —(C.sub.6-C.sub.20)-aryl-(C.sub.1-C.sub.12)-alkyl, —(C.sub.6-C.sub.20)-aryl-O—(C.sub.1-C.sub.12)-alkyl, —(C.sub.3-C.sub.20)-heteroaryl, —(C.sub.3-C.sub.20)-heteroaryl-(C.sub.1-C.sub.12)-alkyl, —(C.sub.3-C.sub.20)-heteroaryl-O—(C.sub.1-C.sub.12)-alkyl, —COOH, —OH, —SO.sub.3H, —NH.sub.2, halogen or a complex comprising Pd and a compound of formula (I).

Description

EXAMPLES

[0134] The examples which follow illustrate the invention.

[0135] General Procedures

[0136] All the preparations which follow were carried out under protective gas using standard Schlenk techniques. The solvents were dried over suitable desiccants before use (Purification of Laboratory Chemicals, W. L. F. Armarego (Author), Christina Chai (Author), Butterworth Heinemann (Elsevier), 6th edition, Oxford 2009).

[0137] Phosphorus trichloride (Aldrich) was distilled under argon before use. All preparative operations were effected in baked-out vessels. The products were characterized by means of NMR spectroscopy. Chemical shifts (6) are reported in ppm. The .sup.31P NMR signals were referenced as follows: SR.sub.31P=SR.sub.1H*(BF.sub.31P/BF.sub.1H)=SR.sub.1H*0.4048. (Robin K. Harris, Edwin D. Becker, Sonia M. Cabral de Menezes, Robin Goodfellow, and Pierre Granger, Pure Appl. Chem., 2001, 73, 1795-1818; Robin K. Harris, Edwin D. Becker, Sonia M. Cabral de Menezes, Pierre Granger, Roy E. Hoffman and Kurt W. Zilm, Pure Appl. Chem., 2008, 80, 59-84).

[0138] The recording of nuclear resonance spectra was effected on Bruker Avance 300 or Bruker Avance 400, gas chromatography analysis on Agilent GC 7890A, elemental analysis on Leco TruSpec CHNS and Varian ICP-OES 715, and ESI-TOF mass spectrometry on Thermo Electron Finnigan MAT 95-XP and Agilent 6890 N/5973 instruments.

Preparation of chloro-2-pyridyl-tert-butylphosphine (Precursor A)

[0139] The Grignard for the synthesis of chloro-2-pyridyl-t-butylphosphine is prepared by the “Knochel method” with isopropylmagnesium chloride (Angew. Chem. 2004, 43, 2222-2226). The workup is effected according to the method of Budzelaar (Organometallics 1990, 9, 1222-1227).

##STR00005##

[0140] 8.07 ml of a 1.3 M isopropylmagnesium chloride solution (Knochel's reagent) are introduced into a 50 ml round-bottom flask with magnetic stirrer and septum, and cooled to −15° C. Thereafter, 953.5 μl (10 mmol) of 2-bromopyridine are rapidly added dropwise. The solution immediately turns yellow. It is allowed to warm up to −10° C. The conversion of the reaction is determined as follows: about 100 μl solution are taken and introduced into 1 ml of a saturated ammonium chloride solution. If the solution “bubbles”, not much Grignard has formed yet. The aqueous solution is extracted with a pipette of ether and the organic phase is dried over Na.sub.2SO.sub.4. A GC of the ethereal solution is recorded. When a large amount of pyridine has formed compared to 2-bromopyridine, conversions are high. At −10° C., there has been little conversion. After warming up to room temperature and stirring for 1-2 hours, the reaction solution turns brown-yellow. A GC test shows complete conversion. Now the Grignard solution can be slowly added dropwise with a syringe pump to a solution of 1.748 g (11 mmol) of dichloro-tert-butylphosphine in 10 ml of THF which has been cooled to −15° C. beforehand. It is important that the dichloro-tert-butylphosphine solution is cooled. At room temperature, considerable amounts of dipyridyl-tert-butylphosphine would be obtained. A clear yellow solution is initially formed, which then turns cloudy. The mixture is left to warm up to room temperature and to stir overnight. According to GC-MS, a large amount of product has formed. The solvent is removed under high vacuum and a whitish solid which is brown in places is obtained. The solid is suspended with 20 ml of heptane and the solid is comminuted in an ultrasound bath. After allowing the white solid to settle out, the solution is decanted. The operation is repeated twice with 10-20 ml each time of heptane. After concentration of the heptane solution under high vacuum, it is distilled under reduced pressure. At 4.6 mbar, oil bath 120° C. and distillation temperature 98° C., the product can be distilled. 1.08 g of a colourless oil are obtained. (50%).

[0141] Analytical data: .sup.1H NMR (300 MHz, C.sub.6D.sub.6): δ 8.36 (m, 1H, Py), 7.67 (m, 1H, Py), 7.03-6.93 (m, 1H, Py), 6.55-6.46 (m, 1H, Py), 1.07 (d, J=13.3 Hz, 9H, t-Bu).

[0142] .sup.13C NMR (75 MHz, C.sub.6D.sub.6): δ 162.9, 162.6, 148.8, 135.5, 125.8, 125.7, 122.8, 35.3, 34.8, 25.9 and 25.8.

[0143] .sup.31P NMR (121 MHz, C.sub.6D.sub.6) δ 97.9.

[0144] MS (EI) m:z (relative intensity) 201 (M*, 2), 147(32), 145 (100), 109 (17), 78 (8), 57.1 (17).

[0145] Preparation of Compound 1

##STR00006## [0146] (Lit: Graham Eastham et al., U.S. Pat. No. 6,335,471)

[0147] 675 mg (27.8 mmol, 4 equivalents) of Mg powder are weighed out in a glovebox in a 250 ml round-bottom flask with a nitrogen tap and magnetic stirrer bar, and the flask is sealed with a septum. High vacuum is applied to the round-bottom flask (about 5×10.sup.−2 mbar) and it is heated to 90° C. for 45 minutes. After cooling down to room temperature, 2 grains of iodine are added and the mixture is dissolved in 20 ml of THF. The suspension is stirred for about 10 minutes until the yellow colour of the iodine has disappeared. After the magnesium powder has settled out, the cloudy THF solution is decanted and the activated magnesium powder is washed twice with 1-2 ml of THF. Then another 20 ml of fresh THF are added. At room temperature, a solution of 755.5 μl (6.9 mmol) of 1,4-dichlorobutane in 70 ml of THF is slowly added dropwise with a syringe pump. The THF solution is clear and pale yellow. The next day, the solution is dark grey but clear and is filtered through Celite. A sample of the Grignard solution is quenched and examined in GC as follows:

[0148] 300 μl of Grignard solution is quenched with 1 ml of a saturated aqueous solution of NH.sub.4Cl and extracted with ether. After drying over Na.sub.2SO.sub.4, a GC of the ether solution is recorded.

[0149] 1,4-Dichlorobutane is no longer detectable, but the butane formed cannot be observed in the GC.

[0150] The content of Grignard compound is determined as follows:

[0151] 1 ml of Grignard solution is quenched with 3 ml of 0.1 M HCl and the excess acid is titrated with 0.1 M NaOH. A suitable indicator is an aqueous 0.04% bromocresol solution. The colour change goes from yellow to blue. 1.70 ml of 0.1 M NaOH has been consumed. 3 ml-1.70 ml=1.3 ml, corresponding to 0.13 mmol of Grignard compound. Since a di-Grignard is present, the Grignard solution is 0.065 M.

[0152] Based on 90 ml of solution this is 85% of Grignard solution. The Grignard can now be reacted with the chlorophosphine:

[0153] In a 250 ml three-neck flask with reflux condenser, magnetic stirrer bar and nitrogen tap, under argon, 1.94 g (9.75 mmol, 2.5 eq) of chloro-2-pyridyl-t-butylphosphine (precursor A) are dissolved in 10 ml of THF and cooled to −60° C. Then 60 ml of the above-stipulated Grignard solution (0.065 M, 3.9 mmol) are slowly added dropwise at this temperature with a syringe pump. The solution at first remains clear and then turns intense yellow. The mixture is left to warm up to room temperature overnight and a clear yellow solution is obtained. To complete the reaction, the mixture is heated under reflux for 2 hours. After cooling, 1 ml of H.sub.2O is added and the solution loses colour and a white solid precipitates out. After removing THF under high vacuum, a stringy, pale yellow solid is obtained. 15 ml of water and 20 ml of ether are added thereto, and two homogeneous clear phases are obtained, which have good separability. The aqueous phase is extracted twice with ether. After the organic phase has been dried with Na.sub.2SO.sub.4, the ether is removed under high vacuum and a viscous, almost colourless oil is obtained. The latter is dissolved in 4 ml of MeOH while heating on a water bath and filtered through Celite. At −28° C., 660 mg of product are obtained in the form of white tacky crystals overnight. (44%).

[0154] .sup.1H NMR (300 MHz, C.sub.6D.sub.6): δ 8.54 (m, 2H, py), 7.37 (m, 2H, py), 6.96 (m, 2H, Py), 6.58 (m, 2H, Py), 2.68 (m, 2H, CH.sub.2), 1.74 (m, 4H, CH.sub.2), 1.52 (m; 2H, CH.sub.2), 1.03 (d, J=11.5 Hz, 18H, tBu).

[0155] .sup.13C NMR (75 MHz, C.sub.6D.sub.6): δ 162.8, 162.5 (q), 149.9, 134.3, 134.1, 132.0, 131.5 and 122.4 (py), 29.4, 29.3, 29.1, 29.0, 20.7, 20.5 (CH.sub.2), 28.1 and 27.9 (tBu).

[0156] .sup.31P NMR (121 MHz, C.sub.6D.sub.6) δ 8.2.

[0157] HRMS (ESI) m/z.sup.+ calculated for: C.sub.22H.sub.34N.sub.2P.sub.2 (M+H)+389.227; found: 389.2273.

[0158] EA calculated for: C.sub.22H.sub.34N.sub.2P.sub.2: C, 68.02; H, 8.82; N, 7.21; P, 15.95. found: C, 68.16; H, 8.97; N, 7.07; P, 15.91.

Preparation of bis(diadamantylphosphinbutane borane Adduct) (Precursor B)

[0159] ##STR00007##

[0160] In a 100 ml round-bottom flask with nitrogen tap and magnetic stirrer bar, 214.7 mg (0.679 mmol) of diadamantylphosphine borane adduct are weighed out. The flask is closed with a septum and, after purging with argon, 10 ml of THF are added. The borane adduct has good solubility in THF, and a clear colourless solution is obtained, which is cooled to −78° C. with dry ice. After stirring for 15 minutes, 0.5 ml (0.70 mmol) of a 1.4 M sec-BuLi solution is slowly added dropwise. After the dropwise addition, a pale yellowish, clear solution is obtained, which is brought to room temperature within 3 hours. The still pale yellowish solution is left to stir at room temperature for a further hour and the solution is cooled back to −78° C. Then 42.6 μl (0.323 mmol) of diiodobutane diluted with 5 ml of THF are slowly added dropwise to this solution. The yellow solution loses colour in the process. The mixture is left to warm up overnight, and a large amount of white solid precipitates out. 8 ml of water are added and the mixture is stirred vigorously for 20 minutes. Further solid floats on top of the solution. The solution is decanted and the white solid is washed three times with MeOH in order to remove any water still present. After drying under reduced pressure, a yield of 210 mg (95%) of a white solid is obtained.

[0161] .sup.1H NMR (300 MHz, CDCl.sub.3): δ 2.11-1.89 (m, 36H, Ad), 1.79-1.68 (m, 24H, Ad), 1.67-1.49 (m, 8H, CH.sub.2), 1.03-(−0.51) (m, broad), 6H, BH.sub.3).

[0162] .sup.13C NMR (75 MHz, CDCl.sub.3): δ 37.8 and 36.6 (Ad), 36.5 and 36.4 (C), 28.1 and 28.0 (Ad), 27.9, 27.7, 15.1 and 14.7 ((CH.sub.2).sub.4).

[0163] .sup.31P NMR (121 MHz, CDCl.sub.3) δ 36.6-33.4 (m).

Preparation of diadamantylphosphine borane Adduct (Precursor C)

[0164] ##STR00008##

[0165] 4.0 g (13.22 mmol) of diadamantylphosphine are weighed out in a 100 ml round bottom flask with nitrogen tap and oval magnetic stirrer bar, closed with a septum and purged. The solid is suspended in 9 ml of THF and 18.9 ml (18.9 mmol, 1 M) of BH.sub.3-THF adduct are added rapidly to this suspension. The suspension at first begins to dissolve. After a while, however, a white solid precipitates out. The mixture is left to stir overnight and the THF is removed under high vacuum. The white residue is taken up in 250 ml of ethyl acetate while heating (60° C.) on a water bath. The borane adduct has good solubility in the warm ethyl acetate. After addition of 6 spoonfuls of silica gel 60 (about 12 g), the solvent is removed completely on a rotary evaporator and the product which has been absorbed on silica gel is chromatographed with a Combi-Flash apparatus. The eluent used is 1:10 (ethyl acetate/heptane). 3.1 g (74%) of diadamantylphosphine borane adduct are obtained.

[0166] .sup.1H NMR (300 MHz, CDCl.sub.3): δ 3.71 (dq, 350.8 Hz and 6.6 Hz, 1H, PH), 2.01-1.94 (m, 18H, Ad), 1.74 (m, 12H, Ad), 1.05-(−0.35) (m, 3H, BH.sub.3).

[0167] .sup.13C NMR (75 MHz, CDCl.sub.3): δ 37.9 and 36.4 (CH.sub.2), 34.8 and 34.4 (C), 28.1 and 28.0 (CH).

[0168] .sup.31P NMR (121 MHz, CDCl.sub.3) δ 42.8-40.0 (m).

Preparation of Ligand 2: bis(diadamantylphosphino)butane (Comparative Ligand)

[0169] ##STR00009##

[0170] 500 mg (0.728 mmol) of borane adduct are weighed out in a 25 ml round-bottom flask with nitrogen tap, and 10 ml of absolute pyrrolidine are added. The suspension is heated under reflux until the solution is colourless and clear (about 2 h). After cooling, the pyrrolidine is removed under high vacuum and a white residue was obtained. This is taken up in 15 ml of toluene and heated to 90° C. The almost clear solution is difficult to filter, since the product precipitates out again in the course of cooling. A white crystalline solid precipitates out of the filtrate in the refrigerator (3° C.). Crystals are washed twice with toluene and dried under high vacuum. 300 mg (62%) of white crystals are obtained.

[0171] Owing to poor solubility at room temperature, a 1H, 13C and 31P NMR in benzene-d6 is recorded at 323 K.

[0172] .sup.1H NMR (323 K, 400 MHz, C.sub.6D.sub.6): δ 2.12-1.92 (m, 16H, CH.sub.2, Ad), 1.92-1.79 (m, 11H, CH.sub.2, Ad), 1.75-1.64 (m, 16H, CH.sub.2, Ad), 1.64-1.47 (m, 6H, CH.sub.2, Ad), 1.45-1.23 (m, 18H, CH.sub.2, Ad).

[0173] .sup.13C NMR (323 K, 100 MHz, C.sub.6D.sub.6): δ 41.5 and 41.4 (Ad), 37.5 (Ad), 36.5 and 36.3 (C), 30.1 (CH.sub.2), 29.3 and 29.2 (Ad), 17.5 and 17.3 (CH.sub.2).

[0174] .sup.31P NMR (323 K, 162 MHz, C.sub.6D.sub.6) δ 25.71.

[0175] High-Pressure Experiments

[0176] Feedstocks:

[0177] Di-n-butene was also referred to as follows: dibutene, DNB or DnB.

[0178] Di-n-butene is an isomer mixture of C8 olefins which arises from the dimerization of mixtures of 1-butene, cis-2-butene and trans-2-butene. In industry, raffinate II or raffinate III streams are generally subjected to a catalytic oligomerization, wherein the butanes present (n/iso) emerge unchanged and the olefins present are converted fully or partly. As well as dimeric di-n-butene, higher oligomers (tributene C12, tetrabutene C16) generally also form, which have to be removed by distillation after the reaction.

[0179] Another process practised in industry for oligomerization of C4 olefins is called the “OCTOL process”.

[0180] Within the patent literature, DE102008007081A1, for example, describes an oligomerization based on the OCTOL process. EP1029839A1 is concerned with the fractionation of the C8 olefins formed in the OCTOL process.

[0181] Technical di-n-butene consists generally to an extent of 5% to 30% of n-octenes, 45% to 75% of 3-methylheptenes, and to an extent of 10% to 35% of 3,4-dimethylhexenes. Preferred streams contain 10% to 20% n-octenes, 55% to 65% 3-methylheptenes, and 15% to 25% 3,4-dimethylhexenes.

[0182] para-Toluenesulphonic acid was abbreviated as follows: pTSA, PTSA or p-TSA. PTSA in this text always refers to para-toluenesulphonic acid monohydrate.

[0183] General Method for Performance of the High-Pressure Experiments

[0184] General experimental method for autoclave experiments in glass vials:

[0185] A 300 ml Parr reactor is used. Matched to this is an aluminium block of corresponding dimensions which has been manufactured in-house and which is suitable for heating by means of a conventional magnetic stirrer, for example from Heidolph. For the inside of the autoclave, a round metal plate of thickness about 1.5 cm was manufactured, containing 6 holes corresponding to the external diameter of the glass vials. Matching these glass vials, they are equipped with small magnetic stirrers. These glass vials are provided with screw caps and suitable septa and charged, using a special apparatus manufactured by glass blowers, under argon with the appropriate reactants, solvents and catalysts and additives. For this purpose, 6 vessels are filled at the same time; this enables the performance of 6 reactions at the same temperature and the same pressure in one experiment. Then these glass vessels are closed with screw caps and septa, and a small syringe cannula of suitable size is used to puncture each of the septa. This enables gas exchange later in the reaction. These vials are then placed in the metal plate and these are transferred into the autoclave under argon. The autoclave is purged with CO and filled at room temperature with the CO pressure intended. Then, by means of the magnetic stirrer, under magnetic stirring, the autoclave is heated to reaction temperature and the reaction is conducted for the appropriate period. Subsequently, the autoclave is cooled down to room temperature and the pressure is slowly released. Subsequently, the autoclave is purged with nitrogen. The vials are taken from the autoclave, and a defined amount of a suitable standard is added. A GC analysis is effected, the results of which are used to determine yields and selectivities.

[0186] Analysis

[0187] GC analysis of di-n-butene: for the GC analysis, an Agilent 7890A gas chromatograph having a 30 m HP5 column is used. Temperature profile: 35° C., 10 min; 10° C./min to 200° C.; the injection volume is 1 μl with a split of 50:1.

[0188] Retention times for di-n-butene and products: 10.784-13.502 min

[0189] The esters formed from di-n-butene are referred to hereinafter as MINO (methyl isononanoate).

[0190] Retention time for ether products of unknown isomer distribution: 15.312, 17.042, 17.244, 17.417 min

[0191] Retention time for iso-C9 esters 19.502-20.439 min (main peak: 19.990 min)

[0192] Retention time for n-C9 esters: 20.669, 20.730, 20.884, 21.266 min.

[0193] Evaluation of the Experiments

[0194] For the evaluation of the catalytic experiments, particular indicators which permit comparison of the various catalyst systems are used hereinafter.

[0195] TON: turnover number, defined as moles of product per mole of catalyst metal, is a measure of the productivity of the catalytic complex.

[0196] TOF: turnover frequency, defined as TON per unit time for the attainment of a particular conversion, e.g. 50%. The TOF is a measure of the activity of the catalytic system.

[0197] The n selectivities reported hereinafter relate to the proportion of terminal methoxycarbonylation based on the overall yield of methoxycarbonylation products.

[0198] The n/iso ratio indicates the ratio of olefins converted terminally to esters to olefins converted internally to esters.

[0199] Methoxycarbonylation of di-n-butene

[0200] Ligand 2 (comparative example): A 25 ml Schlenk vessel was charged with a stock solution of [Pd(acac).sub.2] (1.95 mg, 6.4 μmol), p-toluenesulphonic acid (PTSA) (18.24 mg, 95.89 μmol) and MeOH (10 ml). A 4 ml vial was charged with 2 (2.11 mg, 0.16 mol % based on the molar amount of di-n-butene), and a magnetic stirrer bar was added. Thereafter, 1.25 ml of the clear yellow stock solution and di-n-butene (315 μl, 2 mmol) were added with a syringe. The molar proportions based on the molar amount of di-n-butene are thus 0.04 mol % for Pd(acac).sub.2 and 0.6 mol % for PTSA. The vial was placed into a sample holder which was in turn inserted into a 300 ml Parr autoclave under an argon atmosphere. After the autoclave had been purged three times with nitrogen, the CO pressure was adjusted to 40 bar. The reaction proceeded at 120° C. for 20 hours. On conclusion of the reaction, the autoclave was cooled down to room temperature and cautiously decompressed. Isooctane was added as internal GC standard. Yield and regioselectivity were determined by means of GC. No MINO formation was observed.

[0201] Ligand 1: A 25 ml Schlenk vessel was charged with a stock solution of [Pd(acac).sub.2] (1.95 mg, 6.4 μmol), p-toluenesulphonic acid (PTSA) (18.24 mg, 95.89 μmol) and MeOH (10 ml). A 4 ml vial was charged with 1 (1.24 mg, 0.16 μmol % based on the molar amount of di-n-butene), and a magnetic stirrer bar was added. Thereafter, 1.25 ml of the clear yellow stock solution and di-n-butene (315 μl, 2 mmol) were added with a syringe. The molar proportions based on the molar amount of di-n-butene are thus 0.04 mol % for Pd(acac).sub.2 and 0.6 mol % for PTSA. The vial was placed into a sample holder which was in turn inserted into a 300 ml Parr autoclave under an argon atmosphere. After the autoclave had been purged three times with nitrogen, the CO pressure was adjusted to 40 bar. The reaction proceeded at 120° C. for 20 hours. On conclusion of the reaction, the autoclave was cooled down to room temperature and cautiously decompressed. Isooctane was added as internal GC standard. Yield and regioselectivity were determined by means of GC. (MINO yield: 13%, n/iso regioselectivity: 59/41).

[0202] This experiment shows that the inventive ligand 1 forms a catalytically active palladium complex which catalyses the alkoxycarbonylation of di-n-butene. The structurally similar ligand 2, by contrast, is unsuitable for catalysing alkoxycarbonylation.