Construction of robust ruthenium(salen)(CO) complexes and asymmetric aziridination with nitrene precursors in the form of azide compounds that bear easily removable N-sulfonyl groups.

We synthesized new Ru(salen)(CO) complexes of high durability and achieved aziridination with good to excellent enantioselectivity by using azide compounds that contain an easily removable N-sulfonyl group, such as the 2-(trimethylsilyl)ethanesulfonyl group, as a nitrene precursor. Aziridination of less-reactive alpha,beta-unsaturated esters (and amides) proceeded with excellent enantioselectivities, from which it is inferred that an electrophilic species is the active species of this reaction. The present asymmetric aziridination provides a useful tool for introducing optically active nonprotected amine groups.