Cobalt-Catalyzed Dearomatization of Indoles via Transfer Hydrogenation To Afford Polycyclic Indolines

A cobalt-catalyzed dearomatization of indoles via transfer hydrogenation with HBpin and H₂O has been developed. This reaction offered a straightforward platform to access hexahydro­pyrido­[1,2-a]­indoles in high regio- and chemoselectivity. A preliminary reaction mechanism was proposed on the basis of deuterium-labeling experiments, and a cobalt hydride species was involved in the reaction.