Dioxygen-promoted cobalt-catalyzed oxidative hydroamination using unactivated alkenes and free amines

Abstract

Catalytic Markovnikov-selective hydroamination of unactivated alkenes, in particular by using secondary amines as nucleophiles and/or in an intermolecular setting, remains a challenge. Here we address this problem by developing a cobalt-hydride-catalyzed hydroamination reaction based on a bimetallic redox-triggered oxidative amination pathway. This system enables the use of dioxygen as a sustainable oxidant that is compatible with free amines, while suppressing the facile radical oxygenation that leads to classical Drago-Mukaiyama oxidation. We demonstrate intra- and intermolecular formal addition of secondary amines across unactivated alkenes as well as vinylarenes at ambient temperature. The scope of this method also encompasses alternative nitrogen nucleophiles, such as sulfonamides, amides, and carbamates. Stoichiometric reactions of well-defined organocobalt complexes provide direct evidence for the proposed key amination process.