Process for the preparation of (s)-or (r)-4-halo-3-hydroxybutyrates

摘要

Process for the preparation of enantiomerically pure (S)- or (R)-4-halo-3-hydroxybutyrates of formula (I), wherein R¹ is CH₂X, CHX₂ or CX₃ and X independently represents Cl and/or Br and wherein R² is C_1-6-alkyl, C_3-8-cycloalkyl, aryl or aralkyl, each aryl or aralkyl being optionally further substituted with one or more C_1-4-alkyl groups and/or halogen atoms, by asymmetric hydrogenation of 4-halo-3-oxobutyric acid esters of formula (II), wherein R¹, R² and X are as defined above in the presence of a catalyst of a ruthenium complex comprising a chiral ligand of the formula (III).