Boron aldol reaction of alpha-halosubstituted thioacetates with silyl imines: A highly enantio- and diastereoselective synthesis of aziridines

Boron enolates derived from tert-butyl alpha-halothioacetate and bearing menthone-derived chiral ligands react with imines with excellent diastero- and enantiocontrol to give syn alpha-halo-beta-aminothioesters, which can be converted to the corresponding aziridines by simple ring closure during LAH reduction. A key precursor of antibiotics (+)-thiamphenicol and (-)-florfenicol was synthesized. Copyright (C) 1996 Elsevier Science