Iron-Catalyzed Asymmetric Haloazidation of α,/β-Unsaturated Ketones: Construction of Organic Azides with Two Vicinal Stereocenters

Organic azides play important roles in synthetic chemistry, chemical biology, drug discovery, and material science. Azido-functionalization of alkenes is one of the most efficient procedures for rapid introduction of azide group into organic compounds. But only a few examples have been documented in the catalytic asymmetric version of the azidation of alkenes. Herein, we report an unprecedented highly diastereo- and enantioselective bromoazidation of alpha,beta-unsaturated ketones catalyzed by chiral N,N '-dioxide/Fe(OTf)(2) complexes. An array of aryl, heteroaryl, and alkyl substituted alpha,beta-unsaturated ketones were transformed to the corresponding alpha-bromo-beta-azido ketones in high yields with excellent diastereo- and enantioselectivities. The,catalytic system was also applicable for chloroazidation and iodoazidation of chalcone. Kinetic studies and some control experiments suggested that the reaction might proceed via a 1,4-addition/halogenation pathway.