DE2245829C3 - Process for the preparation of alpha-ketocarboxylic acid esters - Google Patents

Description

O-OH

CH ₃ OH

R — C — C — X + 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 a suspension of the acetylene compound used as the starting material in an alcohol at a temperature which is lower than ⁰ ° C. The reaction is continued until the starting compound has completely disappeared, whereupon the excess ozone is removed and an α-ketocarboxylic acid ester is obtained by reducing the products obtained in the ozonolysis. The type of end product obtained depends on the acetylene compound used as the starting material and the alcohol used.

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

Further examples can be given from the following examples, which are intended to further illustrate the invention Procedural conditions can be seen more clearly.

example 1
Synthesis of methyl benzoylformate

7 g of bromine was diluted with 100 mL of anhydrous methyl alcohol phenylacetylene, and then at a temperature of - a stream of ozone in the mixture obtained initiated 30 ⁰ C, was completely converted to -bromophenylacetylene (was what determined by gas chromatographic monitoring of the reaction). At -30 ^D C, small amounts of solid potassium iodide (31 g) were added while the reaction mixture was stirred magnetically.

The temperature was then raised to room temperature and the mixture was allowed to stand at that temperature for about 30 minutes, followed by the addition of sodium thiosulfate. The mixture 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 yellow oil, 3.140 g of methyl benzoylformate were obtained.

50

Example 2

Synthesis of methyl keto-hexanoate

The mixture was diluted with 5.3 g of 1-bromhexine K), OMI anhydrous methyl alcohol and initiated at a temperature of -30 ⁰ C until the disappearance of 1-bromhexine (gas chromatographic control of the reaction), a stream of ozone in the mixture obtained. Then small amounts of solid potassium iodide (27 g) were added at -3O ^{0 C, 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, after which sodium thiosulfate was added. The reaction mixture was concentrated under reduced pressure, water was added and the mixture was extracted with ethyl ether. The ether extracts were dried over Na ₂ SO ₄ j; and under reduced

reduced tem pressure. By distilling the lead mixture. At -30 ^° C. a small amount was given

The dark yellow oil gave 1.4 g of _r ketone-solid potassium iodide (25 g). The temperature was

methyl hexanoate. then raised to room temperature and left the

Example 3 Stand the mixture at this temperature for 30 minutes,

Synthesis of a-keto-octanoic acid ^{methyl ester s w} ° T ^for ? * " ^Sodium thiosolphate added. The material

³ was then concentrated under reduced pressure,

100 ml of water were added to 5.9 g of 1-bromooctine and the mixture was extracted with ethyl ether, anhydrous methyl alcohol and passed in the case of a. The ether extracts were dried over Na _{? SO4} concentrated temperature of -30 ⁰ C until the disappearance of and under reduced pressure through i-Bromoctin {gas chromatographic control of the io distillation of the remaining dark yellow UIs erReaktion) a stream of ozone by the obtained gave 1.6 g a-keto acid methyl ester .

Claims (1)

Claim: Process for the preparation of a-ketocarboxylic 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 ⁰ C reacts with ozone and then reduced The invention relates to a process for the preparation of α-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 O O -OH - P = P -Y O ₃ are generally unstable at room temperature, although they decompose violently in certain cases. From Japanese Patent 7118979 is the production of free benzoylformic acid by the oxidation of phenylacetylene with selenium dioxide is known It has now been found that there are: n, 1-bromoacetylene compounds so to ozonisies 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 α-ketocarboxylic acid esters. The invention thus relates to a process for the preparation of α-ketocarboxylic acid esters by oxidation of an acetylene compound, which is characterized in that a bromoacetylene compound of the general formula R - C = C - Br, in which R is an optionally substituted aliphatic, cycloaliphatic or aromatic hydrocarbon group, Reacts with ozone in the presence of alcohols at temperatures below OC and then reduced. The process according to the invention can be illustrated by the following reaction scheme: