EP1206590A1

EP1206590A1 - METHOD FOR PRODUCING CARBONYL COMPOUNDS WHICH ARE OXIDIZED IN POSITION $g(a)

Info

Publication number: EP1206590A1
Application number: EP00956251A
Authority: EP
Inventors: Hermann Pütter; Kerstin Schierle-Arndt; Jörg Botzem
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1999-08-06
Filing date: 2000-07-21
Publication date: 2002-05-22
Anticipated expiration: 2020-07-21
Also published as: EP1206590B1; JP2003506575A; DE19937108A1; ATE240425T1; CA2381209A1; US6776894B1; DE50002205D1; WO2001011111A1; ES2199850T3

Abstract

A method for producing compounds which are oxidized in an alpha position by electrochemical reaction with alcohol in the presence of an auxiliary electrolyte and catalytic amounts of a metal salt.

Description

Process for the preparation of carbonyl compounds oxidized in the α-position

description

The present invention relates to a process for the preparation of a compound of the general formula I.

R ²

R ³ UR ^l

OH

in which R ¹ , R ² , R ^{3 are} hydrogen, C 1 -C ₂₀ -alkyl, C ₂ - to C o-alkenyl, C - to C o-alkynyl, C ₃ - to C ₂ -cycloalkyl _/ C ₄ - to C o-cycloalkyl-alkyl, Cι ~ to C ₀ hydroxyalkyl, optionally by Ci to C ₈ alkyl, Cι ~ to C ₈ alkoxy, halogen, Cι ~ to C -haloalkyl, Cι ~ to C ₄ -haloalkoxy, Phenyl, phenoxy,

Halophenyl, halophenoxy, carboxy, C ₂ - to C ₈ -alkoxycarbonyl or cyano-substituted aryl or C - to C o ~ arylalkyl, or R ¹ and R ² or R ³ together, optionally by C 1 -C ₈ -alkyl, C 1 ~ to C ₈ alkoxy and / or halogen mono- to disubstituted C ₂ to C ₉ alkanediyl unit, in which 1 or 2 methyl groups can also be replaced by one unit (CH = CH), and R ³ additionally means one acetalized carbonyl group in which the alkoxy groups are derived from an alcohol of the general formula II

R -OH II

derive, in which R ^{4 represents} -C ~ to C _ß alkyl, means and

U is an acetalized carbonyl group in which the alkoxy groups are derived from an alcohol of the general formula II or a compound of the general formula III

R ³ —V- -R ⁱ III

in which R ^{1 has} the same meaning as in formula I and R ³ exclusively optionally C 1 -C ₈ -alkyl, C 1 -C ₈ -alkoxy, halogen, C 1 -C ₄ -haloalkyl, C 1 -C -haloalkoxy, Phenyl, phenoxy, halophenyl, halophenoxy, carboxy, C - to C ₈ -alkoxycarbonyl or cyano substituted aryl V represents a carbonyl group or has the same meaning as U in formula I and

W has the same meaning as V, with the proviso that one of the groups V or W is a carbonyl group and the other group is an acetalized carbonyl group

or

a compound of the general formula IV

in which R ^{4 has} the same meaning as in formula II, V and W have the same meaning as in formula II and R ^{3 has} the same meaning as in formula III,

by using a compound of the general formula V

R ³ VCR ¹ V

in which V, R ¹ , R ² and R ^{3 have} the same meaning as in formula I or III, with the proviso that

- In the event that a compound of formula III is desired, only such a compound Va is used in which

R ^{1 means} exclusively hydrogen and

R ³ exclusively optionally by Cχ ~ to C ₈ alkyl, Cι ~ to C ₈ alkoxy, halogen, Cι ~ to C ₄ haloalkyl, Ci to C ₄ haloalkoxy, phenyl, phenoxy, halophenyl, halophenoxy, carboxy, C - Aryl substituted to C ₈ -alkoxycarbonyl or cyano and

in the event that compounds of the formula IV are desired, only one compound Vb is used in which

R ¹ and R ^{2 are} exclusively hydrogen, R ³ is optionally optionally by C 1 -C ₈ -alkyl, C 1 -C ₈ -alkoxy, halogen, C 1 -C ₄ -haloalkyl, C 1 -C ₄ -haloalkoxy, phenyl, phenoxy, halophenyl, halophenoxy, carboxy, C - to C ₈ alkoxycarbonyl or

Cyano substituted aryl

electrochemically reacted with an alcohol of the general formula II in the presence of an auxiliary electrolyte and catalytic amounts of a metal salt (S) derived from a metal of the 1st, 2nd, 6th or 8th subgroup or from lead, tin or rhenium.

EP-A-460 451 discloses a process for the preparation of α-hydroxymethyl ketals by electrochemical oxidation of aldehydes or ketones in the presence of alcohols and halogen compounds as auxiliary electrolytes. The reworking of the examples shows that even higher oxidized carbonyl compounds are formed under the described process conditions if the carbonyl group is in the α-position to an aromatic radical. For example, a methylene group in the α position to the carbonyl group can be oxidized to the carbonyl function and, in addition, the originally present carbonyl bond in aldehyde or keto function can be oxidized to the carboxyl group. Not only are α-hydroxy ketals formed, but also α-ketaldehydes, α-ketoacetals, α-ketal carboxylic esters and α-keto orthoesters. However, this process is still not completely satisfactory, since the overall yield of the valuable products mentioned is relatively low and, in addition, large amounts of other largely unusable products are formed.

The unpublished German patent application 19904929 relates to a process for the preparation of 2, 2, 3, 3-tetramethoxypropanol by electrochemical oxidation of methylglyoxaldimethyl acetal using a mixture comprising methanol, water and an auxiliary electrolyte as the electrolysis medium and a cathode made of iron, Steel, platinum or zinc.

The object of the present invention was therefore to provide an electrochemical process with which α-hydroxyketals, α-ketalaldehydes, α-ketoacetals, α-ketalcarboxylic acid esters and α-ketoorthoesters can be produced from carbonyl compounds in keto or aldehyde function in high yields. Accordingly, the method defined above was invented. The process according to the invention is particularly suitable for the preparation of compounds of the general formula I III or IV in which the radical R ⁴ in the acetalized carbonyl group is derived from methanol or ethanol.

Among the compounds of formula I are those of formula la

in which U has the same meaning as in formula I,

n represents 0, 1, 2 or 3 and

R ⁵ Ci to C ₈ alkyl, C ~ to C ₈ alkoxy, halogen, C _3. - bis

C ₄ -Halogenalkyl, C _\ - to C ₄ -haloalkoxy, phenyl, phenoxy, halophenyl, halophenoxy, carboxy, C - to C ₈ -alkoxycarbonyl or cyano means preferred.

Likewise preferred are compounds of the general formula purple

in which n, V, W and R ^{5 have} the same meaning as in formula la or III

or the general formula IVa

in which n, V, W, R ⁴ and R ^{5 have} the same meaning as in formula la or IIla. These compounds are prepared by using, as the starting compound of the general formula V, one of the general formula Va

uses, in which n and R ^{5 have} the same meaning as in formula la.

The process is also particularly suitable for the preparation of compounds of the general formula Ib

H _2rn C _m -CH0H-CH ₂ (OR ⁴ ) ₂ Ib

in which m is a number from 1 to 10 and R ^{4 has} the same meaning as in formula II and for the preparation of which a compound of the general formula Vb

H _2m C _m -CH ₂ -CH0 Vb

starts.

The process is particularly suitable for the production of

- 2-Phenyl-2, 2-dimethoxyethanol, 2-phenyl-2, 2-dimethoxyacetal dehyd and 2-phenylglyoxaldimethylacetal from methanol and acetophenone

α-Hydroxyocatanaldimethylacetal from octanal and

2, 2, 3, 3-tetramethoxypropanol from methylglyocaldimethylacetal.

The auxiliary electrolyte contained in the electrolysis solution is generally a halogen-containing auxiliary electrolyte such as elemental halogen, alkyl halides or halogenated pulp. Halogen-containing salts, in particular iodides or bromides, can also preferably be used. Examples are ammonium halides such as ammonium bromide, ammonium iodide or tetra-butylammonium iodide. Particularly preferred metal halides are furthermore alkali halides such as sodium bromide, sodium iodide, potassium iodide or potassium bromide. The metal salts (S) are preferably those which are derived from mineral acids. The anions of the metal salt are, for example, phosphate, sulfate, nitrate, perchlorate or halide.

The cations of the metal salt (S) are preferably iron, nickel, platinum, palladium, cobalt, zinc, silver or copper ions. The metal salt (S) is generally added to the electrolysis solution in amounts such that the metal ions thereof are present in amounts of 1 to 1000, preferably 5 to 500, preferably 5 to 300 ppm by weight, based on the total amount of the electrolysis liquid.

If necessary, customary solvents are added to the electrolysis liquid. These are the inert solvents generally used in organic chemistry with a high oxidation potential. Examples include dimethyl carbonate or propylene carbonate. In addition to the cosolvents mentioned, water can also be added to the electrolysis liquid, although the water content should not exceed 5% by weight, based on the total amount of the electrolysis liquid.

In general, the electrolysis liquid is composed as follows:

a starting compound of the general formula V

an alcohol of the general formula II

- A halogen-containing auxiliary electrolyte

catalytic amounts of metal salt (S)

where appropriate, the desired products of the general form I, III and IV

optionally other by-products of electrolysis which are derived from the compounds of the general formulas I, II, III, IV and V.

optionally other usual cosolvents

The ratio of the products of the general formulas I and V and the other by-products to the starting compounds in the electrolysis liquid and the ratio of the individual products with different degrees of oxidation is of course dependent on the progress of the reaction.

The ratio of the products of the general formulas I, III, IV and V and the other by-products to the starting

_C onnectivity in the electrolytic liquid and the ratio of the einzelenen products with different oxidation degree to each other is naturally dependent on the reaction progress.

In general, the amount of charge used for the reaction is 1 to 7 F per mole of starting compound of the general formula _V. _B are used evorzugt 3.5 to 4 F, when mixtures are desired, should contain as main components the compounds of formula I and III and 4.5 to 5.5 F, when mixtures are desired, as main components, the compounds of formula I and IV should contain.

The process according to the invention can be carried out in all customary electrolysis cell types. One preferably works with undivided flow cells.

The current densities at which the process is carried out are generally 0.5 to 25 A / dm ² . The temperatures are usually -20 to 60 ° C, preferably 0 to 60 ° C. In general, normal pressure is used. Higher pressures are preferably used when working at higher temperatures to avoid boiling of the starting compounds or cosolvents.

For example, noble metals such as platinum or metal oxides such as ruthenium or chromium oxide or mixed oxides of the Ruo _x TiO _x type are suitable as anode materials. Graphite or carbon electrodes are preferred.

Iron, steel, nickel or precious metals such as platinum and graphite or carbon materials are generally considered as cathode materials.

After the reaction has ended, the electrolysis liquid is worked up using general separation methods. For this purpose, the electrolysis liquid is generally first distilled and the individual compounds are obtained separately in the form of different fractions. Further purification can be carried out, for example, by crystallization or by chromatography. Experimental part

All experiments were carried out in an undivided cell with 11 bipolar electrodes (10 columns, gap distance 1.5 mm).

Current density: 3.4 A / dm ²

Flow: 400 1 / h

Example 1:

Approach: 450 g acetophenone

30 g quay .ium iodide

2460 g of methanol

Fe (III): 5 ppm

Cathode: steel 1. 4301

Anode: graphite

Duration: 7.03 h

Temperature: 36 ° C Amount of charge: 3.5 F.

Current: 5 A.

Turnover:> 99%

Yields of the valuable products:

2-phenyl-2,2-dimethoxy-ethanol: 24% 2-phenyl-2,2-dimethoxy-acetaldehyde: 42%

2-phenylglyoxal dimethyl acetal: 0%

Phenylglyoxylsäuremethylorthoester and 2-phenyl-2,2-dimethoxy-acetic acid methyl ester: 0%

Overall: 66%

Example 2:

Approach: 450 g acetophenone 30 g potassium iodide

2460 g of methanol

Fe (III): 5 ppm

Cathode: graphite Anode: graphite Duration: 7.03 h Temperature: 36 ° C charge quantity; 3.5 F current: 5 A conversion: 84%

Yields of the valuable products:

2-phenyl-2,2-dimethoxyethanol: 15 2-phenyl-2,2-dimethoxyacetaldehyde: 24% 2-phenylglyoxaldimethylacetal: 8%

Phenylglyoxylsäuremethylorthoester and 2-phenyl-2,2-dimethoxy-acetic acid methyl ester: 3%

Total: 50%

Example 3 (4118 / 98-176):

Batch: 450 g acetophenone 90 g potassium iodide 2460 g methanol Fe (III): 5 ppm

Cathode: steel 1.4301

Anode: graphite Duration: 7.03 h

Temperature: 55-58 ° C

Charge amount: 3.5 F

Current: 5 A.

Turnover: 88% yields of valuable products:

2-phenyl-2,2-dimethoxyethanol: 38%

2-phenyl-2,2-dimethoxy-acetaldehyde: 19%

2-phenylglyoxal dimethyl acetal: 12%

Phenylglyoxylsäurernethylorthoester and 2-phenyl-2,2-dimethoxy-acetic acid methyl ester: 1%

Overall: 70%

Example 4

Batch: 450 g acetophenone 90 g potassium iodide 2460 g methanol Fe (III): 5 ppm

Cathode: steel 1.4301 anode: graphite

Duration: 10.47 h

Temperature: 55-58 ° C

Amount of electricity: 5.5 F

Current: 5 A conversion:> 99%

Yields of the valuable products:

2-phenyl-2,2-dimethoxyethanol: 39%

2-phenyl-2,2-dimethoxyacetaldehyde: 0%

2-phenylglyoxaldimethylacetal: 3% phenylglyoxylic acid methyl orthoester and 2-phenyl-2,2-dimethoxyacetic acid methyl ester: 39% In game 5

Approach: 450 g octanal

90 g potassium iodide

2460 g of methanol

Fe (III): 5 ppm

Cathode: MKÜS-F04 (SGL) anode: graphite felt RVG 2003, 6 mm

(German carbon) Duration: 3.76 h

Temperature: 55-58 ° C Amount of current: 2 F Amperage: 5 A Conversion:> 99% Yield: 37% α-hydroxyoctane aldimethvlacetal

Example 6

Batch: 450 g octanal 90 g potassium iodide 2460 g methanol Fe (III): 5 ppm

Cathode: MKUS-F04 (SGL) anode: graphite felt RVG 2003, 6 mm

(German carbon)

Duration: 3.76 h

Temperature: 26-28 ° C

Amount of current: 2 F Amperage: 5 A

Turnover: 97%

Yield: 45% α-hydroxyoctane aldimethylacetal

Example 7:

Batch 450 g of methylglyoxal dimethylacetal

45 g of potassium iodide

2505 g methanol 0.11 g NiS0 ₄

Cathode: graphite Anode: graphite Duration: 5 h Temperature: 30 ° C Current: 5 A Conversion: 52% Selectivity: 59.4%

Yield of 2, 2, 3, 3-tetramethoxypropanol: 31

Comparative Example 1:

Batch: 450 g acetophenone 30 g potassium iodide 2460 g methanol

Cathode: steel 1.4301 anode: graphite

Duration: 7.03 h

Temperature: 36 ° C

Charge amount: 3.5 F

Current: 5 A conversion: 98%

Yields of the valuable products:

2-phenyl-2,2-dimethoxyethanol: 19%

2-phenyl-2,2-dimethoxyacetaldehyde: 12%

2-phenylglyoxal dimethyl acetal: 5% methyl orthoester phenylglyoxylate and methyl 2-phenyl-2,2-dimethoxyacetate: 9%

Overall: 45%

Comparative Example 2:

Approach 450 g acetophenone

30 g potassium iodide

2460 g of methanol

Cathode: graphite Anode: graphite

Duration: 7.03 h

Temperature: 36 ° C

Charge amount: 3.5 F

Current: 5 A conversion: 95%

Yields of the valuable products:

2-phenyl-2,2-dimethoxyethanol: 7%

2-phenyl-2,2-dimethoxyacetaldehyde: 25%

2-phenylglyoxaldimethylacetal: 3% phenylglyoxylic acid methyl orthoester and 2-phenyl-2,2-dimethoxyacetic acid methyl ester: 1%

Overall: 36%

Comparative Example 3

Batch: 450 g octanal 90 g potassium iodide 2460 g of methanol

Cathode: graphite Anode: graphite Duration: 3.76 h

Temperature: 55-58 ° C Amount of current: 2 F Amperage: 5 A Conversion:> 99% Yield: 30%

Comparative Example 4

Approach: 450 g octanal

90 g potassium iodide

2460 g of methanol

Cathode: graphite Anode: graphite Duration: 3.76 h Temperature: 26-28 ° C Current: 2 F Current: 5 A Sales:> 99% Yield: 40%

Comparative Example 5

Batch: 450 g methylglyoxal - dimethylacetal

45 g of potassium iodide

2505 g of methanol

Cathode: graphite Anode: graphite

Duration: 5 h Temperature: 30 ° C

Current: 5 A.

Turnover:> 99%

Selectivity 24.6%

Yield: 2,2,3,3-tetramethoxypropanol 24.6%

Claims

claims

1. Process for the preparation of a compound of the general formula I

R ²

R ³ CR ¹

OH

in which R ¹ , R ² , R ^{3 are} hydrogen, C ₁ to C ₂ o-alkyl, C to C ₂₀ alkenyl, C ₂ to C ₀ alkynyl, C ₃ to C ₁₂ cycloalkyl, C ₄ - to C ₂ o-cycloalkyl-alkyl, C 1 -C ₂₀ -hydroxyalkyl, optionally by C 1 -C ₈ -alkyl, C 1 -C ₈ -alkoxy, halogen, C 1 -C ₄ -haloalkyl, C 1 ~ to C ₄ -Halogenalkoxy, phenyl, phenoxy, halophenyl, halophenoxy, carboxy, C ₂ - to Cs-alkoxycarbonyl or cyano-substituted aryl or C - to C ₂₀ -arylalkyl, or R ¹ and R ² or R ³ together, optionally by Ci to C _8- alkyl, Ci to C ₈ alkoxy and / or halogen mono- to disubstituted C - to C ₉ -alkanediyl unit, in which 1 or 2 methyl groups can also be replaced by one unit (CH = CH) and R ³ additionally an acetalized carbonyl group in which the alkoxy groups are derived from an alcohol of the general formula II

R-0H II

derive, in which R ^{4 is} Cι ~ to Cε-alkyl, means and

R ³ —V — W — R ¹ III

in which R ^{1 has} the same meaning as in formula I and R ³ excluding any Cι ~ to C ₈ alkyl, C ~ to Cs-alkoxy, halogen, Cι ~ to C ₄ haloalkyl, Cι ~ to C ₄ haloalkoxy, Phenyl, phenoxy, halophenyl, halophenoxy, carboxy, C - to Cs-alkoxycarbonyl or cyano substituted aryl V represents a carbonyl group or has the same meaning as U in formula I and

or

a compound of the general formula IV

by using a compound of the general formula V

R ²

R ³ VCR ¹ V

H

R ^{1 means} exclusively hydrogen and

R ³ exclusively optionally by -C ~ to C _ß- alkyl, Ci- to C ₈ -alkoxy, halogen, Cι ~ to C ₄ -haloalkyl, Cι ~ to C ₄ -haloalkoxy, phenyl, phenoxy, halophenyl, halophenoxy, carboxy, C ₂ - to C ₈ -alkoxy carbonyl or cyano substituted aryl and

in the event that a compound of formula IV is desired, only such a compound Vb is used in which

R ¹ and R ^{2 are} exclusively hydrogen, R ³ exclusively optionally through C 1 -C ₈ -alkyl, C 1 -C ₈ -alkoxy, halogen, C _x - to C ₄ -haloalkyl, Cx- to C ₄ -haloalkoxy, phenyl, phenoxy, halophenyl, halophenoxy, carboxy, C - to C ₈ alkoxy carbonyl or cyano substituted aryl

2. The method according to claim 1, for the preparation of a compound of general formula la

in which U has the same meaning as in formula I,

n represents 0, 1, 2 or 3 and

R ⁵ Cι ~ to C _ß alkyl, Cι ~ to C ₈ alkoxy, halogen, Cι ~ bis

C ₄ -haloalkyl, Ci to C ₄ -haloalkoxy, phenyl, phenoxy, halophenyl, halophenoxy, carboxy, C - to C ₈ -alkoxycarbonyl or cyano

or the general formula purple

in which n, V, W and R ^{5 have} the same meaning as in formula la or III

or the general formula IVa

in which n, V, W, R ⁴ and R ^{5 have} the same meaning as in formula la or lilac, by using as the starting compound of the general formula V one of the general formula Va

uses, in which n and R ^{5 have} the same meaning as in formula la.

3. The method according to claim 2, wherein the compound of the general formula la is 2-phenyl-2,2-dimethoxyethanol, the general formula purple is 2-phenyl-2,2-dimethoxyacetal dehyde and 2-phenylglyoxaldimethylacetal, of the general formula IVa Phenylglyoxylsäuremethylorthoester and that of the general formula Va is acetophenone.

4. The method according to claim 1, wherein the compound of general formula I is one of general formula Ib

H _2m C _m -CH0H-CH ₂ (OR ⁴ ) ₂ Ib

in which m is a number from 1 to 10 and R ^{4 has} the same meaning as in formula II and the compound of general formula V is one of general formula Ib

H _2rn C _m -CH ₂ -CHO Vb

acts.

5. The method according to claims 1 to 4, wherein the compound of formula I is 2, 2, 3, 3-tetramethoxypropanol and methylglyoxaldimethylacetal is used as the starting compound.

6. The method according to claims 1 to 5, wherein the anions of the metal salt (S) are derived from mineral acids.

7. The method according to claims 1 to 6, wherein the anions of the metal salt (S) are phosphate, sulfate, nitrate, perchlorate or halide.

8. The method according to claims 1 to 7, wherein the cations of the metal salt (S) are iron, nickel, platinum, palladium, cobalt, zinc, silver or copper.

9. Process according to claims 1 to 8, in which 1 to 1000 ppm by weight of metal ions of the metal salt (S), based on the total amount of the electrolysis liquid, are present in the electrolysis liquid.

10. The method according to claims 1 to 9, wherein the electrolysis liquid contains a halogen-containing auxiliary electrolyte.

11. The method according to claims 1 to 10, wherein the electrolysis liquid consists essentially of

- A starting compound of the general formula V

an alcohol of the general formula II

a halogen-containing auxiliary electrolyte

catalytic amounts of metal salt (S)

optionally the desired products of the general formulas I, III and IV

optionally other by-products of electrolysis which are derived from the compounds of the general formulas I, II, III, IV and V and

- If necessary, other customary cosolvents.

12. The method according to claims 1 to 11, wherein

the proportion of the starting compounds and products of the general formulas I, III, IV and V and the others

By-products of electrolysis from the aforementioned compounds 1 to 70% by weight,

the proportion of the alcohol of the general formula II 14.9 to 94.9% by weight, the proportion of auxiliary electrolyte 0.1 to 5 wt .-% and

the proportion of any cosolvent present is 0 to 70% by weight

based on the electrolysis liquid.

13. The method according to claims 1 to 12, wherein one carries out the electrolysis in an undivided electrolysis cell.

14. The method according to claims 1 to 13, wherein the anodes are those made of noble metals, noble metal oxides, graphite or carbon materials and the cathodes are those made of iron, steel, nickel, zinc, noble metals, graphite or carbon materials.