Chemo- and Enantioselective Intramolecular Silver-Catalyzed Aziridinations of Carbamimidates

Transition metal-catalyzed asymmetric nitrene transfer is a powerful method for the generation of enantioenriched amines frequently found in natural products and bioactive molecules. We report herein a highly chemo- and enantioselective intramolecular silver-catalysed aziridination that uses 2,2,2-trichloroethoxysulfonyl (Tces)-protected carbamimidates as an underexplored class of nitrene precursors. Several homoallylic carbamimidates containing di- and trisubstituted olefins were converted into [4.1.0]-bicyclic aziridines in good-to-excellent yields (up to 98%) and enantioselectivities (up to 99% ee). Computational insights shed insight into the reasons carbamimidates prove superior to the sulfamate and carbamate nitrene precursors that are traditionally used in this chemistry. Post-synthetic modifications afford difunctionalized amines bearing two contiguous, enantioenriched chiral centres.