Chiral lewis acid catalysed asymmetric nucleophilic ring opening of cyclohexene oxide

Abstract

Titanium and zirconium complexes of bispicolinic amides catalyze the ring opening of cyclohexene oxide with trimethylsilyl azide as nucleophile. The product, 1-azido-2-trimethylsilyloxycyclohexane, was obtained in up to 71% enantioselectivity when a catalyst prepared from (S,S)-N,N′-bis(2-pyridinecarboxamide)-1,2-diphenylethane and zirconium tetra-t-butoxide was employed under optimum conditions, which included the addition of a small amount of diethylamine in the catalyst preparation step. The nature of the catalyst is still unknown, but it seems probable that oligomeric metal species are involved.