DE2245829B2 - Process for the preparation of alpha-ketocarboxylic acid esters - Google Patents

Description

The invention relates to a process for the preparation of u-ketocarboxylic acid esters. starting from 1 -Bromoacetylene compounds.

The ozonolysis of acetylene compounds is known in which the acetylene compounds in alcohols react with ozone and give hydroperoxide compounds. The compounds obtained are generally unstable at room temperature, in which case they decompose violently.

From the Japanese patent 7 118 979 the production of free benzoylformic acid is by Oxidation of phenylacetylene with selenium dioxide known.

It has now been found that it is possible to use 1-bromoacetylene compounds to ozonize in such a way that, after going through further process steps, compounds obtained that are stable at room temperature. By working up the reaction mixture is it is then possible to obtain -ketocarboxylic acid esters.

The invention thus relates to a process for the preparation of (i-ketocarboxylic acid esters by oxidation of an acetylene compound, which is characterized in that a bromoacetylene compound of the general formula R - CseeC - Br, where R denotes an optionally substituted aliphatic, cycloaliphatic or aromatic hydrocarbon group, in Reacts the presence of alcohols at temperatures of less than 0 ⁰ C with ozone and then reduced.

The process according to the invention can be illustrated by the following reaction scheme:

R-CsC-X

CH, OH

Ο — OH O Ο —OH 0

Il I /

- R - C - C - X + R - C - C

OCH ₁ X

OCH, OO

Il Il

-> R - C - C - OCH ₃

wherein X is a bromine atom and R has the meanings given above. The ozonization reaction takes place by introducing ozone into a solution or suspension of the starting material! used Acetylene compound in an alcohol at a temperature lower than OC. the The reaction is continued until the starting compound has completely disappeared, whereupon the excess Ozone is removed and one by reducing the products obtained in the ozonolysis an α-ketocarboxylic acid ester is obtained. The nature of the end product obtained thereby depends on that as the starting material acetylene compound used and the alcohol used.

The alcohol can come from a large group. 2. B. from aliphatic, aromatic or cycloaliphatic Alcohols, can be selected.

From the following examples, for further explanation To serve the invention, other process conditions can be more clearly seen.

example 1
Synthesis of benzoyl formic oils

7 g of bromophenylacetylene were diluted with 100 ml of anhydrous methyl alcohol, and then ^{a stream of O / on was passed into the mixture obtained at a temperature of -:} 'i C until bromophenyl acetylene had completely reacted (which was determined by monitoring the reaction by gas chromatography). At - 3O C ¹ small amounts of solid potassium iodide (31 g) was added, during which the reaction mixture was magnetically stirred.

The temperature was then raised to room temperature and the mixture was allowed to stand at that temperature for about 30 minutes, after which time sodium silosulfate was added. The mixture was then concentrated under reduced pressure, treated with water and extracted with ethyl ether. The ether extracts were _{dried over Na, SO 4} and concentrated under reduced pressure. By distilling the remaining dark yellow oil, 3.140 g of benzoylformic acid methyl ester were obtained.

Example 2
Suithesis of methyl n-keto-hexanoic acid

The mixture was diluted with 5.3 g of 1-bromhexine 100 ml of anhydrous methyl alcohol and initiated at a temperature of -. 30 ⁰ C until the disappearance of 1-bromhexine (gas chromatographic Konirolle djr reaction linen stream of ozone in the obtained mixture were then at -30 "C small amounts of solid potassium iodide (27g) were added while the mixture was stirred magnetically. The temperature was then raised to room temperature and the mixture was allowed to stand at that temperature for 30 minutes, followed by addition of sodium thiosulfal / u-6s. The reaction mixture was released under reduced pressure concentrated, mixed with water and extracted with ether. The ether extracts were dried over Na _{: SO 4} and

reduced tem pressure. By distilling the remaining dark yellow oil, 1.4 g of methyl y-ketohexanoate were obtained.

Example 3
Synthesis of methyl a-keto-octanoate

5.9 g of 1-bromooctine were diluted with 100 ml of anhydrous methyl alcohol and a stream of ozone was passed through the mixture obtained at a temperature of -30 ° C. until 1-bromooctine had disappeared (gas chromatographic control of the reaction). A small amount of solid potassium iodide (25 g) was added at -30 ° C. The temperature was then raised to room temperature and the mixture was allowed to stand at that temperature for 30 minutes, followed by the addition of sodium thiosulfate. The material was then concentrated under reduced pressure, treated with water and extracted with ethyl ether. The ether extracts were _{dried over Na 2} SO ₄ and concentrated under reduced pressure. By distilling the remaining dark-dark oil, 1.6 g of u-keto-octanoic acid methyl ester were obtained.

Claims (1)

Claim: Process for the preparation of u-keiocarboxylic acid esters by oxidation of an acetylene compound, characterized in that a bromoacetylene compound of the general formula R - C = C - Br, where R is an optionally substituted aliphatic, cycloaliphatic or aromatic hydrocarbon group, in the presence of alcohols at temperatures of less than 0 ^c C reacts with ozone and then reduced.