Process for making .alpha.,.beta.-unsaturated carboxylic acids
申请人:Hoffmann-La Roche Inc.
公开号:US05910606A1
公开(公告)日:1999-06-08
.alpha., .beta.-Unsaturated acids of the formula ##STR1## wherein R.sup.1 signifies C.sub.1 -C.sub.5 -alkyl and Ar signifies an aryl group which is optionally substituted by one or more substituents selected from the group consisting of halogen, phenyl, C.sub.1 -C.sub.5 -alkyl, C.sub.1 -C.sub.5 -alkoxy, perfluorinated C.sub.1 -C.sub.5 -alkyl or perfluorinated C.sub.1 -C.sub.5 -alkoxy can be obtained from new or known compounds of the formula ##STR2## Compounds I can be converted by asymmetric hydrogenation into corresponding optically active saturated acids.
route was developed for the synthesis of (S)2-(4-fluorophenyl)-3-methylbutanoic acid (S)-2 with an overall yield of 80% starting from 4-fluorophenylacetic acid. Asymmetrichydrogenation of the easily accessible unsaturatedacid 3 in the presence of ruthenium(II) carboxylato complexes containing chiral atropisomeric diphosphines afforded (S)-2 in up to 94% ee. The ee of (S)-2 was upgraded to 98% by crystallization