Method for preparing di- or tricarboxylic esters by alkoxycarbonylation of dienes having conjugated double bonds

Abstract

The invention relates to a method for preparing di- or tricarboxylic esters by alkoxycarbonylation of dienes having conjugated double bonds. The method includes the steps of initially charging a diene having two conjugated double bonds, adding a phosphine ligand according to formula (I) and a catalyst precursor, adding an alcohol, feeding in CO, and heating the reaction mixture with conversion of the diene to a di- or tricarboxylic ester. ##STR00001##

Claims

1. A method for preparing di- or tricarboxylic esters in a reaction mixture, comprising the method steps of: a) initially charging a diene having two conjugated double bonds, wherein the diene is selected from compounds of the formula (II) ##STR00033## where R.sup.7, R.sup.8, R.sup.9, R.sup.10 may each independently be selected from H, (C.sub.1-C.sub.12)-alkyl, or (C.sub.6-C.sub.20)-aryl; b) adding a phosphine ligand and a catalyst precursor selected from palladium dichloride, palladium dibromide, palladium diiodide, palladium(II) acetylacetonate, palladium(II) acetate, bis(dibenzylideneacetone)palladium, bis(acetonitrile)dichloropalladium(II), or palladium (cinnamyl) dichloride; c) adding an alcohol; d) feeding in CO; e) heating the reaction mixture, with conversion of the diene to a di- or tricarboxylic ester; wherein the phosphine ligand is a compound according to formula (I) ##STR00034## where R.sup.1, R.sup.2, R.sup.3, R.sup.4 are selected from (C.sub.1-C.sub.12)-alkyl, (C.sub.6-C.sub.20)-aryl, (C.sub.3-C.sub.12)-cycloalkyl, (C.sub.3-C.sub.12)-heterocycloalkyl, or (C.sub.3-C.sub.20)-heteroaryl; R.sup.5, R.sup.6 are selected from H, (C.sub.1-C.sub.12)-alkyl, (C.sub.6-C.sub.20)-aryl, (C.sub.3-C.sub.12)-cycloalkyl, (C.sub.3-C.sub.12)-heterocycloalkyl, or (C.sub.3-C.sub.20)-heteroaryl; and R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, in the case that these are (C.sub.1-C.sub.12)-alkyl, (C.sub.6-C.sub.20)-aryl, (C.sub.3-C.sub.12)-cycloalkyl, (C.sub.3-C.sub.12)-heterocycloalkyl or (C.sub.3-C.sub.20)-heteroaryl, may be each substituted independently of one another 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, or halogen, and wherein steps a), b), c), and d) may be effected in any sequence.

2. The method according to claim 1, where R.sup.1, R.sup.2, R.sup.3, R.sup.4 are selected from (C.sub.1-C.sub.12)-alkyl, (C.sub.6-C.sub.20)-aryl, or (C.sub.3-C.sub.20)-heteroaryl.

3. The method according to claim 1, where R.sup.5, R.sup.6 are selected from H or (C.sub.1-C.sub.12)-alkyl.

4. The method according to claim 1, where R.sup.1, R.sup.2, R.sup.3, R.sup.4 are each (C.sub.6-C.sub.20)-aryl and R.sup.5, R.sup.6 are each selected from H or (C.sub.1-C.sub.12)-alkyl.

5. The method according to claim 1, wherein the diene has 4 to 30 carbon atoms.

6. The method according to claim 1, wherein the catalyst precursor is selected from palladium dichloride, palladium dibromide, palladium diiodide, palladium(II) acetylacetonate, palladium(II) acetate, or bis(dibenzylideneacetone)palladium.

7. The method according to claim 1, wherein the catalyst precursor is selected from palladium dichloride, palladium dibromide, or palladium diiodide.

8. The method according to claim 1, wherein the alcohol in method step c) has 1 to 12 carbon atoms.

9. The method according to claim 1, wherein the alcohol in method step c) is selected from methanol, ethanol, 1-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 1-hexanol, cyclohexanol, 2-ethylhexanol, isononanol, 2-propylheptanol, benzyl alcohol, 1-phenylethanol or 2-phenylethanol.

10. The method according to claim 1, wherein the alcohol in method step c) is selected from methanol, ethanol, isopropanol, n-butanol or 2-phenylethanol.

11. The method of claim 1, wherein R.sup.7, R.sup.8, R.sup.9, R.sup.10 may each independently be selected from H, (C.sub.1-C.sub.6)-alkyl, or phenyl.

Description

EXAMPLES

(1) The examples which follow illustrate the invention.

(2) General Procedure Specifications

(3) Unless stated otherwise, relative molar amounts in mol % refer to the molar amount of olefin (substrate).

(4) All reaction products were isolated from the reaction mixture by column chromatography over silica gel 60, 0.063-0.2 mm, 70-230 mesh from Merck.

(5) Gel chromatography analyses (GC analyses) were carried out using an instrument of the Agilent GC 7890A type from Agilent using an HP5 column (polydimethylsiloxane with 5% phenyl groups, 30 m, 0.32 mm i.d., 0.25 m film thickness). Temperature program: 35 C., 10 min.; 10 C./min to 285 C., 5 min.; injection volume 1 l with a split of 50:1. The retention times of the purified products are specified in the following table:

(6) TABLE-US-00001 Product Retention time (min) 22.0 23.6 24.3 27.4 0 35.3 28.0 28.5 31.6 35.1
Alkoxycarbonylation of Isoprene with n-Butanol Using Different Ligands

(7) ##STR00015##

(8) A 4 ml sample vial was charged with PdBr.sub.2 (2.64 mg, 1.0 mol %), PTSA (9.5 mg, 5.0 mol %), the respective ligand (2.0 mol %) and a magnetic stirrer bar. The vial was sealed with a septum (PTFE-coated styrene-butadiene rubber) and a phenol resin cap. Gas exchange between sample vial and environment was enabled by means of a cannula pierced through the septum. The sample vial was purged three times with argon. Para-xylene (2.0 ml), isoprene (100 l, 1.0 mmol) and n-butanol (274 l, 3.0 mmol) were injected into the sample vial by means of a syringe. The sample vial was placed on a metal plate and this was transferred under an argon atmosphere into a 300 ml autoclave of the 4560 type from Parr Instruments. After the autoclave had been purged three times with CO, the CO pressure was adjusted to 40 bar at room temperature. The reaction ran for 48 hours at 120 C. After completion of the reaction, the autoclave was cooled to room temperature and carefully decompressed. Isooctane (100 l) was added as internal GO standard. The yield of dicarboxylic ester (3a) and monocarboxylic ester (4a) was determined by GC. The results are compiled in the following table. The ligands used in each case are commercially available compounds.

(9) TABLE-US-00002 Example Ligand Yield 3a Yield 4a 1 No ligand 68% 2* .sup.89% 11% 2 0 42% 3 0 42% 4 0 0.sup. *inventive example

(10) As this experiment shows, ligand 1, used according to the invention as sole ligand investigated, is capable of converting isoprene in one step to a dicarboxylic acid. With ligands 2 to 4 described in the prior art in the context of alkoxycarbonylation of isoprene (cf. X. Fang et al, Angew. Chem. Int. Ed., 2014, 53, 9030-9034) at best monoesters but no dicarboxylic esters are obtained.

(11) Alkoxycarbonylation of Isoprene with n-Butanol Using Different Catalyst Precursors

(12) A 4 ml sample vial was charged with 1.0 mol % or 0.5 mol % of the respective catalyst precursor, PTSA (9.5 mg, 5.0 mol %), ligand 1 (11.6 mg, 2.0 mmol %) and a magnetic stirrer bar. The vial was sealed with a septum (PTFE-coated styrene-butadiene rubber) and a phenol resin cap. Gas exchange between sample vial and environment was enabled by means of a cannula pierced through the septum. The sample vial was purged three times with argon. Para-xylene (2.0 ml), isoprene (100 l, 1.0 mmol) and n-butanol (274 l, 3.0 mmol) were injected into the sample vial by means of a syringe. The sample vial was placed on a metal plate and this was transferred under an argon atmosphere into a 300 ml autoclave of the 4560 type from Parr Instruments. After the autoclave had been purged three times with CO, the CO pressure was adjusted to 40 bar at room temperature. The reaction ran for 48 hours at 140 C. After completion of the reaction, the autoclave was cooled to room temperature and carefully decompressed. Isooctane (100 l) was added as internal GC standard. The yield of dicarboxylic ester (3a) and monoester (4a) was determined by GC. The results are compiled in the following table.

(13) TABLE-US-00003 Example Catalyst precursor Yield 3a Yield 4a 1 1.0 mol % PdCl.sub.2 71% 26% 2 1.0 mol % PdBr.sub.2 89% 11% 3 1.0 mol % PdI.sub.2 67% 19% 4 1.0 mol % Pd(OAc).sub.2 41% 32% 5 1.0 mol % Pd(acac).sub.2 44% 27% 6 0.5 mol % Pd.sub.2(dba).sub.3 24% 52%

(14) This experiment shows that direct conversion of isoprene to dicarboxylic ester can be achieved with different catalyst precursors used in accordance with the invention. The best results are achieved here using PdCl.sub.2, PdBr.sub.2, PdI.sub.2.

(15) Alkoxycarbonylation of Different Dienes with Different Alcohols

(16) A 4 ml sample vial was charged with PdBr.sub.2, PTSA, ligand 1 in the amount specified and a magnetic stirrer bar. The vial was sealed with a septum (PTFE-coated styrene-butadiene rubber) and a phenol resin cap. Gas exchange between sample vial and environment was enabled by means of a cannula pierced through the septum. The sample vial was purged three times with argon. Para-xylene (2.0 ml), 1.0 mmol of diene and 3.0 mmol of alcohol were injected into the sample vial by means of a syringe. The sample vial was placed on a metal plate and this was transferred under an argon atmosphere into a 300 ml autoclave of the 4560 type from Parr Instruments. After the autoclave had been purged three times with CO, the CO pressure was adjusted to 40 bar at room temperature. The reaction ran for 48 or 96 hours at 140 C. After completion of the reaction, the autoclave was cooled to room temperature and carefully decompressed. Isooctane (100 l) was added as internal GC standard. The yield of the main product was determined by means of GC analysis. The results are compiled in the following table.

(17) TABLE-US-00004 Example.sup.1) Diene Alcohol Main product Yield 1 Isoprene Methanol 0 76% 2 Isoprene Ethanol 82% 3 Isoprene Isopropanol 70% 4 Isoprene n-Butanol 94% 5 Isoprene 2-Phenylethanol 94% 6 n-Butanol 79% 7 n-Butanol 99% 8 n-Butanol 0 30% 9 n-Butanol 37% .sup.1)examples 1 to 5, 7 and 8: 1.0 mol % PdBr.sub.2, 2.0 mol % ligand 1, 5.0 mol % PTSA, 48 h; examples 6 and 9: 2.0 mol % PdBr.sub.2, 4.0 mol % ligand 1, 10.0 mol % PTSA, 96 h.

(18) The examples described above show that 1,3-dienes, isoprene for example, may be converted directly to di- or tricarboxylic esters with the method according to the invention. This is an advantage compared to the two-step method for preparing dicarboxylic esters in the prior art. Use of different alcohols was also shown to be successful.