The first examples of dynamic kinetic resolution by enantioselective acetylation of hemithioacetals: An efficient synthesis of homochiral α-Acetoxysulfides

Abstract

The Pseudomonas fluorescens lipase catalysed irreversible acetylation of a hemithioacetal using vinyl acetate proceeds via a novel dynamic kinetic resolution. Thus a thiol and an aldehyde are mixed together to form a racemic hemithioacetal, essentially a single enantiomer of which is acylated under the reaction conditions. Racemisation of the unrecognised hemithioacetal by a dissociation-recombination process catalysed by silica gel, allows greater than 50% conversion in the reaction. High yields and enantioselectivities can be obtained with suitable substrates.