Preparation of enantiomerically enriched P-stereogenic dialkyl-arylphosphine oxides via coordination mediated optical resolution

Abstract

Optical resolution of several dialkyl-arylphosphine oxides was elaborated using the Ca2+ salt of (-)-O, O'-dibenzoyl-(2R,3R)-tartaric acid as the resolving agent. The conditions of crystallization and purification of the enantiomerically enriched phosphine oxides were optimized. Ethyl-phenyl-propylphosphine oxide and butyl-methyl-phenylphosphine oxide were prepared with an enantiomeric excess higher than 93%, whereas, three other dialkyl-arylphosphine oxides were obtained with an enantiomeric excess of 37-85%. It was also found that the sterically demanding alkyl chains hinder the formation of stable diastereomeric complexes, which consequently led to less efficient resolution procedures.