Catalytic,Enantloselective Ring Opening of Aziridines

摘要

The asymmetric ring opening of meso epoxides is being used increasingly in the enantioselective synthesis of 1,2-difunc-tionalized fine chemicals.However,until recently there was no efficient method for the related aziridines,which is surprising in view of the potential of this reaction,for example,in the direct synthesis of valuable,optically pure 1,2-diamines.In principle,owing to the similarly large ring strain,the ring opening of aziridines should be about as facile as that of epoxides,especially when the aziridine nitrogen atom is activated electronically by electron-withdrawing substituents,such as acyl or tosyl groups.However,the substituent on the N atom can be aligned either cis or trans to other ring substituents through pyrimidal inversion at this position,which leads to competitive transition states in the case of Lewis acid catalyzed reactions and can thus complicate a subsequent selective reaction.