Formal enantioselective synthesis of (−)-allosamizoline using chiral diamine-catalyzed asymmetric aziridination of cyclic enones

Abstract

We developed a highly effective organocatalytic system for asymmetric aziridination of cyclic enones. Catalytic asymmetric aziridination of 2-cyclopenten-1-one with t-butyl p-toluenesulfonyloxy carbamate proceeded using 20 mol % of (1R,2R)-1,2-diphenylethylenediamine derivative with an N-4,4-dimethylcyclohexyl group 1h, producing chiral aziridine ketone (1R,5R)-4 in 82% yield with 99% ee. Organocatalyst 1h was also an effective catalyst for the asymmetric aziridination of other cyclic enones. The obtained chiral aziridine ketone (1R,5R)-4 could be successfully transformed into the key intermediate for the synthesis of (−)-allosamizoline, demonstrating the utility of this asymmetric aziridination for the synthesis of aminocyclopentitol derivatives.