METHOD FOR THE ALKOXYCARBONYLATION OF ETHYLENICALLY UNSATURATED COMPOUNDS USING CO2 AND A ZINC COMPOUND

Description

[0001] The invention relates to a process for the alkoxycarbonylation of ethylene unsaturated compounds using CO2 and a zinc compound.

[0002] EP 4 001 256 A1 describes a process for the alkoxycarbonylation of ethylene unsaturated compounds using benzene-based diphosphine ligands and aluminium triflate.

[0003] CN 115 403 465 A describes a process for the production of carboxylates by reacting olefins with CO 2.

[0004] An article by Wu, L., Liu, Q., Fleischer, I. et al. in Nat Commun 5, 3091 (2014), https: / / doi.org / 10.1038 / ncomms4091, describes a ruthenium-catalyzed alkoxycarbonylation of alkenes with carbon dioxide.

[0005] The technical objective of the invention is to provide a new process which should deliver an increased yield of esters.

[0006] The problem is solved by a method according to claim 1.

[0007] The procedure encompasses the following procedural steps: a) Providing an ethylene unsaturated compound; b) Adding a ligand according to formula (1): where R1<, R2<, R3<, R4< each represent -(C1-C12)-alkyl, R5<, R6< each represent a residue selected from: -H, -O-(C1-C12)-alkyl, -(C1-C12)-alkyl, and a compound comprising Pd; c) addition of a zinc compound; d) addition of an alcohol; e) supply of CO2 and H2; f) heating of the reaction mixture from a) to e), whereby the ethylene unsaturated compound is converted to an ester.

[0008] The term (C 1 -C 12 )-alkyl includes straight-chain and branched alkyl groups with 1 to 12 carbon atoms.

[0009] In one variant of the procedure, R 1< , R 2< , R 3< , R 4< represent -(C 1 -C 4 )-alkyl.

[0010] In one variant of the procedure, R 1< , R 2< , R 3< , R 4< represent - tert< Bu.

[0011] In one variant of the procedure, R 5< , R 6< represent a residue selected from: -H, -O-(C 1 -C 4 )-alkyl.

[0012] In one variant of the procedure, R 5< , R 6< represent a residue selected from: -H, -OCH 3 .

[0013] In one variant of the procedure, the ligand exhibits the structure ( 1 ) or ( 2 ) on:

[0014] In one variant of the procedure, the ligand exhibits the structure ( 1 ) on:

[0015] In one variant of the procedure, the ligand exhibits the structure ( 2 ) on:

[0016] In one variant of the process, the compound in process step b), which comprises Pd, is selected from: palladium dichloride, palladium(II) acetylacetonate, palladium(II) acetate (Pd(OAc) 2 ), dichloro(1,5-cyclooctadiene)palladium(II), bis(dibenzylideneacetone)palladium (Pd(dba) 2 ), bis(acetonitrile)dichloropalladium(II), palladium(cinnamyl)dichloride

[0017] In one variant of the procedure, the compound in procedure step b), which includes Pd, is selected from: Pd(dba) 2 , Pd(OAc) 2 .

[0018] In one variant of the process, the zinc compound is selected from: Zn(OTf) 2 , Zn(SO 3 C 6 H 4 CH 3 )·xH 2 O, Zn(SO 3 CH 3 )·xH 2 O.

[0019] In one variant of the process, the zinc compound Zn(OTf) 2 .

[0020] In one variant of the process, the alcohol in process step d) is selected from: methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, tert-Butanol, 3-Pentanol, Cyclohexanol, Phenol, or mixtures thereof.

[0021] In one variant of the process, the alcohol in process step d) is selected from: methanol, ethanol, 1-butanol.

[0022] In one variant of the process, CO2 is supplied at a pressure in the range of 1 MPa (10 bar) to 5 MPa (50 bar).

[0023] In one variant of the process, CO2 is supplied at a pressure in the range of 1 MPa (10 bar) to 3 MPa (30 bar).

[0024] In one variant of the process, H2 is supplied at a pressure in the range of 1 MPa (10 bar) to 5 MPa (50 bar).

[0025] In one variant of the process, H2 is supplied at a pressure in the range of 1 MPa (10 bar) to 3 MPa (30 bar).

[0026] In one variation of the process, the heating takes place to a temperature in the range of 80 °C to 160 °C.

[0027] In one variation of the process, the heating takes place to a temperature in the range of 100 °C to 140 °C.

[0028] The invention will now be explained in more detail using exemplary embodiments. Variation of the additive

[0029]

[0030] The solid starting materials are palladium precursor Pd(dba) 2 (2.9 mg, 0.005 mmol), ligand ( 21,2-Bis(di-tert-butylphosphinomethyl)benzene (dt < bpx) (0.01 mmol) and additive X (0.05 mmol) were weighed and transferred in a glovebox to a 12 mL screw-top vial with a 6 mm magnetic stir bar. The vial was sealed with a Teflon / silicone septum and a phenolic resin cap and then removed from the glovebox. The vial was connected to a Schlenk line with a needle under an argon stream. Distilled methanol (2.0 mL) and distilled 1-octene (157 µL, 1.0 mmol) were injected using a standard syringe or a microliter syringe. The vial was held on an alloy plate and placed in a Parr 4560 series autoclave (300 mL). The autoclave was purged twice with nitrogen gas at room temperature. In addition, the system was rinsed twice with carbon dioxide and carbon dioxide was pressurized up to 20 bar, after which hydrogen (at 20 bar) was added up to a total pressure of 40 bar.The mixture was heated to 140 °C and stirred for 20 hours (600 rpm). The autoclave was then cooled with ice water, after which the gas was carefully vented. The solution was treated with isooctane (83 µl, 0.5 mmol) as an internal standard, filtered through Celite, and analyzed by gas chromatography. Reaction conditions:

[0031] Pd(dpa) 2 (0.005 mmol), ligand (2) dt< bpx (0.01 mmol), additive (variable) (0.05 mmol), MeOH, CO 2 (20 bar), H 2 (20 bar), 140 °C, 20 h Table 1: Additive Yield 2a n:iso Yield 3a + 4a Zn(OTf) 2 25 % 92 : 8 74 % Zn(SO 3 C 6 H 4 CH 3 ) xH 2 O 14 % 92 : 8 85 % Zn(SO3CH3)·xH2O 23 % 94 : 6 76 % PTSA·H₂O - - 98 % Al(OTf) 3 - - 98 % Fe(OTf) 3 - - 98 %

[0032] The experiments with PTSA·H 2 O, Al(OTf) 3 and Fe(OTf) 3 are comparative experiments. Ligand variation

[0033]

[0034] The series of experiments was conducted analogously to the Variation of the additiveThe experiments were carried out, except that Zn(OTf)₂ was always used as the additive in this series, and the ligand varied. 0.01 mmol of the ligand was always used. Reaction conditions:

[0035] Pd(dpa) 2 (0.005 mmol), ligand (variable) (0.01 mmol), additive: Zn(OTf) 2 (0.05 mmol), MeOH, CO 2 (20 bar), H 2 (20 bar), 140 °C, 20 h Table 2: Ligand Yield 2a n:iso Yield 3a + 4a (2) 25 % 92 : 8 74 % (1) 33 % 92 : 8 65 % (3) 2 % - 97 % (4) < 1 % - 98 %

[0036] In the experiments with ligand (3) and (4) These are comparative tests. Variation of the ethylene unsaturated compound / of alcohol

[0037] The series of experiments was carried out according to the previously described experiments, using the following reaction conditions: Reaction conditions:

[0038] Pd(OAc) 2 (0.03 mmol), ligand (2)dt< bpx (0.06 mmol), additive: Zn(OTf) 2 (0.05 mmol), MeOH, CO 2 (20 bar), H 2 (20 bar), 120 °C, 45 h Table 3: Methoxycarbonylation unsaturated compound(s) / product(s) yield n:iso 83 % 93 : 7 69 % 93 : 7 82 % 93 : 7 12 % 47 % 44 % 25 % 42 % 62 : 38 15 % 99 : 1 18 % 99 : 1 17 % 99 : 1 8 % 99 : 1 21 % 32 % 98 : 2 14 % 90 : 10 21 % 80 : 20

[0039] In the following series of experiments, ethanol was used instead of methanol. Reaction conditions:

[0040] Pd(OAc) 2 (0.03 mmol), ligand (2) dt< bpx (0.06 mmol), additive: Zn(OTf) 2 (0.05 mmol), EtOH, CO 2 (20 bar), H 2 (20 bar), 120 °C, 45 h Table 4: Ethoxycarbonylation unsaturated compound(s) / product(s) yield n:iso 68 % 93 : 7 66 % 94 : 6 54 % 94 : 6 16 % 30 % 29 % 98 : 2

[0041] In the following series of experiments, 1-butanol was used as the alcohol. Reaction conditions:

[0042] Pd(OAc) 2 (0.03 mmol), ligand (2) dt< bpx (0.06 mmol), additive: Zn(OTf) 2 (0.05 mmol), 1-butanol, CO 2 (20 bar), H 2 (20 bar), 120 °C, 45 h Table 5: Butyloxycarbonylation unsaturated compound(s) / product(s) yield n:iso 28 % 92 : 8 21 % 92 : 8 23 % 92 : 8

[0043] As the experiments carried out show, the problem is solved by a method according to the invention.

Claims

1. Process comprising the process steps of: a) initially charging an ethylenically unsaturated compound; b) adding a ligand of formula (I): where R1, R2, R3, R4 are each -(C1-C12)-alkyl, R5, R6 are each a radical selected from: -H, -O-(C1-C12)-alkyl, -(C1-C12)-alkyl, and a compound comprising Pd; c) adding a zinc compound; d) adding an alcohol; e) feeding in CO2 and H2; f) heating the reaction mixture of a) to e), with conversion of the ethylenically unsaturated compound to an ester.

2. Process according to Claim 1, where R1, R2, R3, R4 are -(C1-C4)-alkyl.

3. Process according to either of Claims 1 and 2, where R5, R6 are a radical selected from: -H, -O-(C1-C4)-alkyl.

4. Process according to any of Claims 1 to 3, wherein the ligand has the structure (1) or (2):

5. Process according to any of Claims 1 to 4, wherein the ligand has the structure (1):

6. Process according to any of Claims 1 to 4, wherein the ligand has the structure (2):

7. Process according to any of Claims 1 to 6, wherein the compound in process step b) which comprises Pd is selected from: palladium dichloride, palladium(II) acetylacetonate, palladium(II) acetate (Pd(OAc)2), dichloro(1,5-cyclooctadiene)palladium(II), bis(dibenzylideneacetone)palladium (Pd(dba)2), bis(acetonitrile)dichloropalladium(II), palladium(cinnamyl) dichloride.

8. Process according to any of Claims 1 to 7, wherein the compound in process step b) which comprises Pd is selected from: Pd(dba)2, Pd(OAc)2.

9. Process according to any of Claims 1 to 8, wherein the zinc compound is selected from: Zn(OTf)2, Zn(SO3C6H4CH3)·xH2O, Zn(SO3CH3)·xH2O.

10. Process according to any of Claims 1 to 9, wherein the zinc compound is Zn(OTf)2.

11. Process according to any of Claims 1 to 10, wherein the alcohol in process step d) is selected from: methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, tert-butanol, 3-pentanol, cyclohexanol, phenol, or mixtures thereof.

12. Process according to any of Claims 1 to 11, wherein the alcohol in process step d) is selected from: methanol, ethanol, 1-butanol.

13. Process according to any of Claims 1 to 12, wherein CO2 is fed in with a pressure in the range from 1 MPa (10 bar) to 5 MPa (50 bar).

14. Process according to any of Claims 1 to 13, wherein H2 is fed in with a pressure in the range from 1 MPa (10 bar) to 5 MPa (50 bar).

15. Process according to any of Claims 1 to 14, wherein the reaction mixture is heated to a temperature in the range from 80°C to 160°C.