CHIRAL LEWIS-ACID CATALYZED ASYMMETRIC NUCLEOPHILIC RING-OPENING OF CYCLOHEXENE OXIDE

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.