Method for converting an ether into the corresponding ester

Abstract

The invention relates to a method for converting an ether into the corresponding ester.

Description

[0001] Process for converting an ether into the corresponding ester

[0002] The present invention relates to a process for converting an ether into the corresponding ester.

[0003] Caprylic acid (n-octanoic acid) is an important industrial compound with a wide range of applications, such as in the food industry or pharmaceuticals.

[0004] In contrast to its extraction from plant products, pure n-octanoic acid can be obtained through chemical production. This is traditionally achieved by telomerization of 1,3-butadiene with water to form 2,7-octadienol. The unsaturated aldehyde is obtained by isomerization of the alcohol. Hydrogenation of 7-octenal to octanal and subsequent oxidation of the octanal ultimately yields the desired n-octanoic acid. ung

[0005] This multi-step process produces a large amount of byproducts and is quite energy-intensive. The objective of the present invention was to optimize substeps of the previously described synthesis route for producing acids. This should contribute to a more efficient synthesis route.

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

[0007] Process comprising the process steps: a) introducing an ether having 5 to 30 carbon atoms which has at least two double bonds; b) adding a ligand according to formula (I): where

[0008] R 1 , R 2 , R 3 , R 4 each represent -(Ci-Ci2)-alkyl,

[0009] R 5 , R 6each represents a radical selected from: -H, -O-(Ci-Ci2)-alkyl, -(C Ci2)-alkyl, and a compound comprising Pd; c) adding a Lewis acid; d) heating the reaction mixture from a) to c), wherein the ether is converted to an ester, and the ester has the same number of carbon atoms as the ether.

[0010] The term (Ci-Ci2)-alkyl includes straight-chain and branched alkyl groups with 1 to 12 carbon atoms.

[0011] The process according to the invention allows caprylic acid to be produced in a significantly more efficient way: proper implementation

[0012] In a variant of the process, the ether has the formula (II):

[0013] R® ,R 7

[0014] 0 (II) and

[0015] R 6 represents a carbon chain which has at least four C atoms and at least two double bonds;

[0016] R7 stands for a carbon chain which has at least one C atom.

[0017] In a variant of the procedure, R 7 for a carbon chain with 1 to 4 C atoms.

[0018] In a variant of the procedure, R 6 for a carbon chain with 5 to 12 C atoms.

[0019] In a variant of the procedure, R 6 for a carbon chain which has exactly two double bonds.

[0020] In a variant of the process, the ether has the structure (2): In a variant of the process, the ether is obtained by telomerization of 1,3-butadiene.

[0021] In a variant of the process, the ether is obtained by telomerization of 1,3-butadiene with methanol.

[0022] In a variant of the procedure, R 5 , R 6 for -H.

[0023] In a variant of the procedure, R1 , R 2 , R 3 , R 4 for -(Ci-C4)-alkyl.

[0024] In a variant of the procedure, R 1 , R 2 , R 3 , R 4 for - f Bu.

[0025] In a variant of the process, the ligand has the structure (1):

[0026] In a variant of the process, the compound in process step b) which comprises Pd is selected from: palladium dichloride, palladium dibromide, palladium diiodide, palladium(II) acetylacetonate, palladium(II) acetate, dichloro(1,5-cyclooctadiene)palladium(II), bis(dibenzylideneacetone)palladium, bis(acetonitrile)dichloropalladium(II), palladium(cinnamyl)dichloride.

[0027] In a variant of the process, the compound in process step b) which comprises Pd is selected from: Pd(dba)2, Pd(OAc)2, Pdl3.

[0028] In a variant of the process, the Lewis acid is selected from: Al(OTf)3, Ga(OTf)3, ln(OTf)3, Bi(OTf)3, Fe(OTf)3, Al(OMs)3, Al(OTs)3.

[0029] In one variant of the process, the Lewis acid is present as a sulfonated tetrafluoroethylene polymer. In one variant of the process, heating in process step d) takes place at a temperature in the range of 70 °C to 140 °C.

[0030] In a variant of the process, heating in process step d) takes place to a temperature in the range of 80 °C to 120 °C.

[0031] In a variant of the process, the process comprises the additional process step c'): c') addition of a solvent.

[0032] In one variant of the process, the solvent is methanol.

[0033] In a variant of the process, the process comprises the additional process step e): e) hydrolysis of the ester obtained in d) to the acid.

[0034] In the following, the invention will be explained in more detail using exemplary embodiments.

[0035] The experiments were carried out with 1.0 mmol of 1-MODE (2) in a methanol solution (2.0 mL). Pd(dba)2 (dba: dibenzylideneacetone) as precursor, 1,2-bis(di-tert-butylphosphinomethyl)benzene (d t bpx) (1) was used as the ligand and Al(OTf)3 (OTf: trifluoromethanesulfonate) as the Lewis acid. A nitrogen pressure of 40 bar was used. The reaction proceeded for 6 hours at 100 °C.

[0036] Reaction conditions:

[0037] Pd(dba)20.5 ​​mol%, ligand (1) 1.0 mol%, Al(OTf)32.0 mol%, MeOH, N240 bar, T: 100 ° C, t: 6 h

[0038] The yield of ester was 85%.

[0039] The experiment was carried out in modified variations:

[0040] - without AI(OTf)3: no yield

[0041] - without Pd(dba)2: no yield

[0042] Variation of the Pd compound

[0043] The experiment was carried out with different Pd compounds.

[0044] The results are summarized in the following table: Table 1 :

[0045] Variation of the Lewis acid

[0046] The experiment was carried out with different Lewis acids.

[0047] The results are summarized in the table below.

[0048] Reaction conditions:

[0049] Pd(dba)2 0.5 mol%, ligand (1) 1.0 mol%, Lewis acid 2.0 mol%, MeOH, N2 40 bar, T: 100 ° C, t:

[0050] 20 hours

[0051] Table 2:

[0052] Comparison experiment with a Bronsted acid

[0053] Reaction conditions:

[0054] Pd(dba) 20.5 mol%, ligand (1) 1.0 mol%, acid 2.0 mol%, MeOH, N240 bar, T: 100 ° C, t: 6 h

[0055] Table 3: non-inventive comparative test

[0056] As the tests carried out show, the problem is solved by a method according to the invention.

Claims

Patent claims 1 . A process comprising the process steps: a) introducing an ether having 5 to 30 carbon atoms which has at least two double bonds; b) adding a ligand according to formula (I): where R 1 , R 2 , R 3 , R 4 each represent -(Ci-Ci2)-alkyl, R 5 , R 6 each represents a radical selected from: -H, -O-(Ci-Ci2)-alkyl, -(C Ci2)-alkyl, and a compound comprising Pd; c) adding a Lewis acid; d) heating the reaction mixture from a) to c), wherein the ether is converted to an ester, and the ester has the same number of carbon atoms as the ether.

2. The process according to claim 1, wherein the ether has the formula (II): R 3 ,R 7 0 (II) and R 6represents a carbon chain which has at least four C atoms and at least two double bonds; R 7 stands for a carbon chain which has at least one C atom.

3. The method according to claim 2, wherein R 7 stands for a carbon chain with 1 to 4 C atoms.

4. A process according to any one of claims 2 or 3, wherein R 6 stands for a carbon chain with 5 to 12 C atoms.

5. A process according to any one of claims 2 to 4, wherein R 6 stands for a carbon chain which has exactly two double bonds.

6. A process according to any one of claims 1 to 5, wherein the ether has the structure (2):

7. A process according to any one of claims 1 to 6, wherein R 5 , R 6 stand for -H.

8. The method according to any one of claims 1 to 7, wherein the ligand has the structure (1):

9. The process according to any one of claims 1 to 8, wherein the compound in process step b) which comprises Pd is selected from: palladium dichloride, palladium dibromide, palladium diiodide, palladium(II) acetylacetonate, palladium(II) acetate, dichloro(1,5-cyclooctadiene)palladium(II), bis(dibenzylideneacetone)palladium, bis(acetonitrile)dichloropalladium(II), palladium(cinnamyl)dichloride.

10. The process according to any one of claims 1 to 9, wherein the compound in process step b) which comprises Pd is selected from: Pd(dba)2, Pd(OAc)2, Pdl2.

11. The process according to any one of claims 1 to 10, wherein the Lewis acid is selected from: Al(OTf)3, Ga(OTf)3, In(OTf)3, Bi(OTf)3, Fe(OTf)3, Al(OMS)3, Al(OTS)3.

12. Method according to one of claims 1 to 11, wherein the heating in process step d) is carried out to a temperature in the range from 70 °C to 140 °C.

13. The process according to any one of claims 1 to 12, wherein the process comprises the additional process step c'): c') adding a solvent.

14. A process according to any one of claims 1 to 13, wherein the process comprises the additional process step e): e) hydrolysis of the ester obtained in d) to the acid.

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