Generation of oxiranyllithiums and oxiranyl Grignard reagents having a carbanion-destabilizing group from sulfinyloxiranes: Their property and an application to asymmetric synthesis of epoxides and alcohols

The first generation of oxiranyllithiums and oxiranyl Grignard reagents having a carbanion-destabilizing group (alkyl group) was realized from sulfinyloxiranes via the ligand exchange reaction of sulfoxides with tert-butyllithium or ethylmagnesium chloride in THF at -80 to -100 degrees C. The generated oxiranyllithiums were found to be very unstable; however, these anions reacted with several electrophiles to give epoxides in up to 86% yield. The oxiranyl Grignard reagents were found to be more stable and much less reactive than the oxiranyllithiums. The reactivities of the oxiranyllithiums having several alkyl groups were investigated. As an application of the method, optically active tri- and tetra-substituted epoxides and alcohols were synthesized from optically active chloromethyl p-tolyl sulfoxide via the oxiranyllithiums. (C) 1999 Elsevier Science Ltd. All rights reserved.