Asymmetric aziridination: a new entry to optically active non-N-protected aziridines

A newly designed robust Ru(salen)(CO) complex 3 was found to catalyze asymmetric aziridination using azide compounds carrying p-nitrobenzenesulfonyl and 2-(trimethylsilyl)ethanesulfonyl (SES) groups, which are easily removable N-protecting groups under mild conditions, as a nitrene precursor in a highly enantioselective manner. In particular, the reactions with SES azide showed excellent enantioselectivity greater than 90% ee, except for one example.