Preparation of optically active 2-halopropionic acids

Details Preparation of optically active 2-halopropionic acids Preparation of optically active 2-halopropionic acids

1997-07-01

1998-06-09

Killos, Paul J.

Textiles: spinning, twisting, and twining

C07C 5315

Patent

active

057636591

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BRIEF SUMMARY
optically active 2-halopropionic acids. sodium salt thereof by alkaline hydrolysis of isobutyl l-2-chloropropionate. During this process however, a poor-quality product (ca 90 to 95 % of excess enantiomer) is often formed, which still contains 5 to 10 % of lactic acid as by-product. o-silylized silylized ketenacetals to react with N-chlorosuccinimide and the hydrolysis thereof with alkali metal hydroperoxides to form l-2-chloropropionic acid. possible to dissociate racemic 2-chloropropionates enantio-selectively by means of enzymes. However, a disadvantage of this is, apart from the maximum possible yield of only 50 % - based on racemate -, the insufficient enantiomer purity of the 2-chloropropionates formed. cylindracea is also known (US 898,972). phenoxypropionates are obtained by enzymatic esterification of the corresponding racemic acids, one of the enantiomers being esterified whilst the other remains as acid, depending on the enzyme used. Separation of the optically active compounds is then carried out by distillation and/or extraction. Depending on process conditions used concentrations of the d- or l-isomers of from 70 % to ca 95 % are obtained. the d-enantiomer is converted into lactic acid and the l-chloropropionic acid remains unchanged. The maximum possible yields are approximately 50 % --based on racemate --(Biocatalysis, D.A. Abramowicz CZ (Ed) van Nostrand R. N.Y. (1990), Journal of General Microbiology 128, 1755 (1982)). d,l-2- bromopropionate is used as racemate and is converted into methyl l-(-)-2- bromopropionate by means of Candida cylindracea lipase in a two-phase system. 995 (1987) describe the lipase-catalyzed hydrolysis of methyl l-2-chloropropionate in the presence of carbon tetrachloride. The disadvantage of this method is, apart from the use of a chlorinated solvent, the low yield of ca 30 % at an enantiomer purity of only 95 %. of racemic 2-chloropropionates in a two-phase system comprising water and a substantially water-immiscible organic solvent for the ester. This process is very elaborate, since the organic phase must a number of times be separated, brought into contact with the hydrolase, and recycled. Since only incomplete conversion takes place and no enantiomer-pure products are obtained despite relative long reaction times, this method is unsuitable for commercial manufacture of l-2- chloropropionic acid and the sodium salt thereof. acids are racemate dissociations of 2-halocarboxamides with microorganisms such as pseudomones (DE 4,117,255 A1) and 2-halocarboxylic acid nitrites by means of microorganisms (Pure and Appl. Chem. 62, 1441 (1990)). the preparation of optically active 2-halopropionic acids having as high a chemical 25 and optical purity as possible (at least ca 98 % excess enantiomer). active 2- halopropionic acids, wherein the corresponding optically active alkyl 2-halopropio- nates are caused to react with a carboxylic acid at elevated temperature in a transacylation reaction with the formation of the optically active 2-halopropionic acid and the alkyl carboxylate, and the optically active 2-halopropionic acid obtained is separated from the reaction mixture. reaction equation ##STR1## In which I is the optically active alkyl 2-halopropionate in which X denotes halogen, II is the carboxylic acid, III is the optically active 2-halopropionic acid obtained, and IV is the alkyl carboxylate formed during transacylation. 2-halopropionic acids III, X denotes chlorine, bromine, or iodine, preferably chlorine or bromine and more preferably chlorine. preferably C1 -C6 alkyl, and R2 generally denotes hydrogen or C1 -C4 alkyl. and propionic acid, preferably formic acid or acetic acid and more preferably formic acid. as starting product is advantageously carried out starting from the corresponding optically active lactates by halogenation thereof. For example, the preparation of alkyl l-2-chloropropionates is carried out by halogenation of the corresponding alkyl d-lactates by replacing the hydroxyl group by chlorine. The alkyl d-lactates may be chlorinated in known man

REFERENCES:
patent: 5049676 (1991-09-01), Metivier et al.
patent: 5278054 (1994-01-01), Buchner et al.
Chem. Abst. JP 2 104 560, 1990.
Chem. Abst. JP 71 068 445, 1986.
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