High-performance anionic stereogenic-at-cobalt(iii) complex/halide salts/oxone catalytic system for enantioselective halocyclization of olefins†

A high-performance anionic stereogenic-at-cobalt(iii) complex/oxone catalytic system was developed for various enantioselective intramolecular halocyclizations of olefins using halide salts as halogen sources, delivering structurally diverse halogenated heterocyclic compounds with outstanding stereoselectivity (up to 97 : 3 e.r.). In this protocol, ultra-low catalyst loadings can be routinely used, since the stereogenic-at-cobalt(iii) complexes were the sole counteranions of cationic halonium intermediates, minimizing background reactions to the greatest extent possible.