Monophosphine compounds and palladium catalysts based thereon for the alkoxycarbonylation of ethylenically unsaturated compounds

Abstract

The invention relates to compounds of formula (I) ##STR00001## where R.sup.1 is selected from (C.sub.1-C.sub.12)-alkyl, (C.sub.3-C.sub.12)-cycloalkyl, (C.sub.3-C.sub.12)-heterocycloalkyl; R.sup.2 is selected from (C.sub.3-C.sub.12)-heterocycloalkyl, (C.sub.6-C.sub.20)-aryl, (C.sub.3-C.sub.20)-heteroaryl; R.sup.3 is (C.sub.3-C.sub.20)-heteroaryl; and R.sup.1, R.sup.2 and R.sup.3 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, COO(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. The invention further relates to Pd complexes comprising the compound according to the invention and to the use thereof in alkoxycarbonylation.

Claims

1. Compound of formula (I) ##STR00010## where R.sup.1 is selected from the group consisting of (C.sub.1-C.sub.12)-alkyl, (C.sub.3-C.sub.12)-cycloalkyl and (C.sub.3-C.sub.12)-heterocycloalkyl; R.sup.2 is selected from the group consisting of phenyl, pyrimidyl and 2-imidazolyl; R.sup.3 is 2-imidazolyl; and R.sup.1, R.sup.2 and R.sup.3 may each independently be substituted by one or more substituents selected from the group consisting of (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-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 and halogen.

2. Compound according to claim 1, where R.sup.1 is (C.sub.1-C.sub.12)-alkyl.

3. A compound having formulae (1) ##STR00011##

4. Complex comprising Pd and a compound of formula (I) ##STR00012## where R.sup.1 is selected from the group consisting of (C.sub.1-C.sub.12)-alkyl, (C.sub.3-C.sub.12)-cycloalkyl and (C.sub.3-C.sub.12)-heterocycloalkyl; R.sup.2 is selected from the group consisting of phenyl, pyrimidyl and 2-imidazolyl; R.sup.3 is imidazolyl; and R.sup.1, R.sup.2 and R.sup.3 may each independently be substituted by one or more substituents selected from the group consisting of (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-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 and halogen.

5. Process comprising the following process steps: a) initially charging an ethylenically unsaturated compound; b) adding a compound of formula (I) ##STR00013## where R.sup.1 is selected from the group consisting of (C.sub.1-C.sub.12)-alkyl, (C.sub.3-C.sub.12)-cycloalkyl and (C.sub.3-C.sub.12)-heterocycloalkyl; R.sup.2 is selected from the group consisting of phenyl, pyrimidyl and 2-imidazolyl; R.sup.3 is imidazolyl; and R.sup.1, R.sup.2 and R.sup.3 may each independently be substituted by one or more substituents selected from the group consisting of (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-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 and halogen, and a compound comprising Pd, or adding a complex according to claim 4; c) adding an alcohol; d) feeding in CO; e) heating the reaction mixture, with conversion of the ethylenically unsaturated compound to an ester.

6. Process according to claim 5, wherein the ethylenically unsaturated compound is selected from the group consisting of 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.

7. Process according to claim 5, wherein the compound comprising Pd in process step b) is selected from the group consisting of palladium dichloride, palladium(II) acetylacetonate, palladium(II) acetate, dichloro(1,5-cycloocta-diene)palladium(II), bis(dibenzylideneacetone)palladium, bis(acetonitrile)dichloro-palladium(II) and palladium(cinnamyl) dichloride.

8. Process according to claim 5, wherein the alcohol in process step c) is selected from the group consisting of methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, tert-butanol, 3-pentanol, cyclohexanol, phenol and mixtures thereof.

9. Process according to claim 5, wherein the alcohol in process step c) is an aliphatic alcohol.

10. A process for catalysis of an alkoxycarbonylation reaction, comprising: introducing a compound of formula (I) ##STR00014## where R.sup.1 is selected from the group consisting of (C.sub.1-C.sub.12)-alkyl, (C.sub.3-C.sub.12)-cycloalkyl and (C.sub.3-C.sub.12)-heterocycloalkyl; R.sup.2 is selected from the group consisting of phenyl, pyrimidyl and 2-imidazolyl; R.sup.3 is imidazolyl; and R.sup.1, R.sup.2 and R.sup.3 may each independently be substituted by one or more substituents selected from the group consisting of (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-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 and halogen or a complex according to claim 4.

Description

EXAMPLES

(1) The invention is described in detail hereinafter by working examples.

(2) General Procedures

(3) 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).

(4) 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 (?) 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).

(5) 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)

(6) 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).

(7) ##STR00005##

(8) 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 ?l (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 ?l 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%).

(9) Analytical data: .sup.1H NMR (300 MHz, C.sub.6D.sub.6): ? 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).

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

(11) .sup.31P NMR (1213 MHz, C.sub.6D.sub.6) ? 97.9.

(12) MS (EI) m:z (relative intensity) 201 (M.sup.+, 2), 147 (32), 145 (100), 109 (17), 78 (8), 57.1 (17).

Preparation of Compound 1

(13) ##STR00006##

(14) 0.78 g (9.5 mmol) of 1-methylimidazole are weighed out in a 50 ml three-neck flask with thermometer and dropping funnel under argon and dissolved in 10 ml of THF. Then 1.6 ml of TMEDA are added to the solution. The mixture is then cooled down to ?78? C. Thereafter, 6 ml of 1.6 N n-butyllithium in hexane are added dropwise by means of a dropping funnel. The 50 ml flask containing the reaction mixture is left to stir at room temperature for 30 min. Subsequently, 1.5 g of tert-butyldichlorophosphine are dissolved in 20 ml of THF. Then the 1-methylimidazole-BuLi mixture is added dropwise to the tert-butyldichlorophosphine at ?78? C. Thereafter, the mixture is warmed to room temperature. A product precipitates out. The suspension is filtered and the residue is dissolved in water and then washed three times with dichloromethane. The organic phase is dried with Na.sub.2SO.sub.4 and then the solvent is removed under reduced pressure. The residue is dissolved with 5 ml of dichloromethane and blanketed with 20 ml of diethyl ether. The product crystallizes. The product was obtained in an amount of 0.8 g.

(15) Purity (NMR)=98%,

(16) .sup.31P NMR (CD.sub.2Cl.sub.2, 121 MHz)=?32.25 ppm,

(17) .sup.13C NMR (CD.sub.2Cl.sub.2, 75 MHz)=144 s, 130.2 d (J.sub.PC=3.7 Hz), 123.8 s, 34.2 d, (J.sub.PC=11.7 Hz), 25.9 d, (J.sub.PC=14.3 Hz)

(18) .sup.1H NMR (CD.sub.2Cl.sub.2, 300 MHz): 7.04, d, (J=1 Hz, 1H), 6.94 dd (J=1 Hz, J=1.5 Hz, 1H), 3.4 s (6H), 1.2 d (J=14.6 Hz, 9H)

(19) HRMS: calculated for C.sub.12H.sub.19N.sub.4P: 251.14201, found: 251.14206.

Preparation of 2-(tert-butyl(phenyl)phosphino)pyridine (Compound 2)

(20) ##STR00007##

(21) 3.4 g (16.8 mmol) of 2-(tert-butylchlorophosphino)pyridine (precursor A) are dissolved under argon in 50 ml of absolute diethyl ether in a 100 ml three-neck flask provided with a low-temperature thermometer and magnetic stirrer. The mixture is cooled down to ?78? C. At this temperature, within 10 minutes, 10 ml of a 1.8 N phenyllithium solution (in dibutyl ether) are added by means of a dropping funnel. The mixture is stirred at this temperature for 10 minutes and then warmed to room temperature and stirred for a further half an hour. This solution is washed three times with 10 ml of degassed water. The organic phase is then distilled under a fine vacuum of 10.sup.?1 Torr. The product is obtained at this pressure at 130? C. as a clear liquid in a high purity of greater than 97% (NMR). The yield is 3.85 g (93%).

(22) Analysis:

(23) .sup.31P (acetone-d.sub.6, 121 MHz), 16.31 s,

(24) .sup.13C (75 MHz, acetone-d.sub.6, 165.1 (d, J.sub.PC=10.5 Hz), 150.3 (d, J.sub.PC=5 Hz), 137.3 s, 137.0 s, 136.7 s, 135.9 d, 135.9 (d, J.sub.PC=7.6 Hz), 131.1 s, 130.6 s, 130.2 s, 128.9 (d, J.sub.PC=8 Hz), 122.9 s, 32.1 (d, J.sub.PC=13.1 Hz), 28.5 (d, J.sub.PC=13.7 Hz),

(25) .sup.1H (acetone-d.sub.6, 300 MHz):

(26) 8.74 (dm, J=4.7 Hz), 7.7-7.6 m (2H), 7.4-7.3 (m, 3H), 7.28-7.23 (m, 1H), 1.2 (d, J=12.6 Hz, 9H)

(27) MS (EI, 70 eV): m/z (%), 243 (M+, 17), 203 (65), 187 (78), 156 (6), 126 (8), 109 (100), 78 (11), 57 (11), HRMS (EI), calculated for C15H18N1P1: 243.11714, found: 243.11753.

(28) Further Ligands

(29) The following comparative compounds are commercially available.

(30) ##STR00008##

(31) Alkoxycarbonylation Experiments

(32) General Experiment Description for Reactions in Batchwise Mode:

(33) The appropriate amounts of substrate, palladium salt, acid and alcohol are mixed under argon in a 50 ml Schlenk vessel while stirring with a magnetic stirrer.

(34) A 100 ml steel autoclave from Parr provided with a gas inlet and a gas outlet valve, a digital pressure transducer, a temperature sensor and a ball valve, and an installed capillary for sampling, is freed of oxygen by means of vacuum and argon purging three times. Subsequently, the reaction solution from the Schlenk vessel is introduced by means of a capillary into the autoclave in an argon counterflow through the ball valve. Subsequently, either the appropriate amount of CO is injected at room temperature and then the autoclave is heated up to reaction temperature (reactions that are not run under constant pressure) or the autoclave is first heated up to reaction temperature and then the CO is injected by means of a burette connected to the autoclave by means of a pressure reducer. This burette is then filled with CO to about 100 bar and, during the reaction, supplies the CO required at a constant pressure. This burette has a dead volume of about 30 ml and is provided with a digital pressure transducer. Then the reaction is conducted at the required temperature for the required time while stirring. In the course of this, by means of software (Specview from SpecView Corporation) and a Parr 4870 process controller and a 4875 power controller, data for the pressure variation in the autoclave and in the gas burette are recorded. These data are used to generate Excel tables, which are used at a later stage to create diagrams which show gas consumptions and hence conversions over time. If required, via the capillary, the GC samples are collected and analysed. For this purpose, a suitable exact amount (2-10 ml) of isooctane as internal standard is also added to the Schlenk vessel before the reaction. These also give information about the course of the reaction. At the end of the reaction, the autoclave is cooled down to room temperature, the pressure is cautiously released, isooctane is added if necessary as internal standard, and a GC analysis or, in the case of new products, a GC-MS analysis is conducted.

(35) General Experimental Method for Autoclave Experiments in Glass Vials

(36) 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.

(37) Analysis:

(38) Methanol Analysis

(39) Methanol was pretreated in a solvent drying system: Pure Solv MD Solvent Purification System, from Innovative Technology Inc., One Industrial Way, Amesbury Mass. 01013

(40) Water Values:

(41) Determined by Karl Fischer Titration: TitraLab 580-TIM580, from Radiometer Analytical SAS (Karl Fischer titration), water content: measurement ranges: 0.1-100% w/w, water content measured: 0.13889%

(42) The following were used:

(43) Technical-grade methanol: Applichem: Nr A2954,5000, batch number: LOT: 3L005446, water content max. 1%

(44) Methanol: Acros Organics (over molecular sieve): water content 0.005%, code number: 364390010, batch number: LOT 1370321

(45) Methoxycarbonylation of Ethene

(46) A 50 ml Schlenk vessel was charged with Pd(acac).sub.2 (6.53 mg, 0.04 mol %), ligand (0.16 mol %), ethene (1.5 g, 53 mmol), 20 ml of methanol and para-toluenesulphonic acid (PTSA, 61 mg, 0.6 mol %). The reaction mixture was transferred by means of a capillary in an argon counterflow into a 100 ml steel autoclave as described above. The CO pressure was adjusted to 40 bar. The reaction proceeded at 80? C. for 3 hours. On conclusion of the reaction, the autoclave was cooled down to room temperature and cautiously decompressed.

(47) Isooctane (100 ?l) was added as internal GC standard. Yield and selectivity were determined by means of GC.

(48) The results are shown in the following table:

(49) TABLE-US-00001 Ligand Yield 1 30% 2 14% 3 (CE) 3% 10 (CE) 0% CE: comparative example

(50) This example shows that the inventive ligands 1, 2 achieve much better yields in the methoxycarbonylation of ethene than the comparative ligands 3 and 10.

(51) Isomerizing Regioselective Methoxycarbonylation of 1-Octene

(52) ##STR00009##

(53) The iso/n ratio reported hereinafter indicates the ratio of olefins converted internally to esters to olefins converted terminally to esters.

(54) a) Variant with PdCl.sub.2

(55) A 4 ml vial was charged with PdCl.sub.2 (1.77 mg, 1.0 mol %) and ligand (4.0 mol %), and a magnetic stirrer bar was added. Then toluene (2 ml), 1-octene (157 ?l, 1 mmol) and MeOH (40.5 ?l, 1 mmol) were injected with a syringe. 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 (100 ?l) was added as internal GC standard. Yield and regioselectivity were determined by means of GC.

(56) The results are shown in the following table:

(57) TABLE-US-00002 Ligand Yield iso/n 2 75% 28/72 3 (CE) 87% 55/45 10 (CE) 10% 45/55 CE: comparative example; Cy: cyclohexyl; o-tol: ortho-tolyl; Ph: phenyl; .sup.tBu: tert-butyl.

(58) The inventive ligand 2 features both a higher yield and a high n/iso selectivity. By contrast, the ligand 10 known from the prior art achieves only a low yield and is additionally not regioselective. The comparative ligand 3 does achieve a high yield, but is likewise not regioselective.

(59) b) Variant with Pd(acac).sub.2

(60) A 25 ml Schlenk vessel was charged with [Pd(acac).sub.2] (1.95 mg, 0.04 mol %), p-toluenesulphonic acid (PTSA) (18.24 ?l, 0.6 mol %) and MeOH (10 ml). A 4 ml vial was charged with the ligand (0.16 mol %), and a magnetic stirrer bar was added. Thereafter, 1.25 ml of the clear yellow solution from the Schlenk vessel and 1-octene (315 ?l, 2 mmol) were injected with a syringe. 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 (100 ?l) was added as internal GC standard. Yield and regioselectivity were determined by means of GC.

(61) The results are shown in the following table:

(62) TABLE-US-00003 Ligand Yield iso/n 2 26% 74/26 3 (CE) 16% 77/23 10 (CE) 0% N/A CE: comparative example

(63) Here too, the inventive ligand 2 exhibits a high iso/n selectivity and a higher yield than comparative ligands 3 and 10.