Preparation of chiral alpha-halocarboxylic acids

摘要

Prepn. of an optically active alpha -(chloro or bromo)-alkanoic acid, salt or deriv. of formula R(CH2)n-CH2-CHX-COOM (I) comprises enantiomer-selective hydrogenation of an alpha , beta -unsatd. alkenoic acid deriv. of formula (II) in presence of a ruthenium complex (III) of an optically active (pref. atropisomeric) diphosphine ligand. X = Cl or Br; M = H, N(R1)4<+>, alkali metal or alkaline earth metal cation; R1 = H or lower alkyl; n = 0 or 1; R = H or 1-20C alkyl (opt. terminally substd. by N(R2)2, COOR2, OR3, opt. protected CHO or opt. substd. ring); R2 = H or lower alkyl; R3 = H or protecting gp.