Cobalt(III)-catalyzed asymmetric ring-opening of 7-oxabenzonorbornadienes via indole C–H functionalization

Abstract

Asymmetric ring-opening of 7-oxabenzonorbornadienes is achieved via Co-catalyzed indole C–H functionalization. The utilization of chiral Co-catalyst consisting of a binaphthyl-derived trisubstituted cyclopentadienyl ligand resulted in high yields (up to 99%) and excellent enantioselectivity (>99% ee) for the target products with tolerance for diverse functional groups. Opposite diastereoselectivities are obtained with chiral Co-catalyst or Cp*CoI₂CO. Combined experimental and computational studies suggest β-oxygen elimination being the selectivity-determining step of the reaction. Meanwhile, the reactions of 7-azabenzonorbornadiene could also be executed in a diastereodivergent manner.

Asymmetric ring-opening (ARO) reactions, which can help quickly build molecular complexity, have not been extensively shown via β-oxygen elimination. Here, the authors report a cobalt(III)-catalyzed ARO reaction, providing mechanistic insights and the origins of the diastereo- and enantioselectivity.