Cobalt-Catalyzed Cyclohydrocarbonylations: Syntheses of Saturated Heterocycles Promoted by Light

A general strategy for the syntheses of valuable saturated heterocycles via regio- and stereoselective cyclohydrocarbonylation is reported. This annulation uses a simple cobalt catalyst and visible light under mild conditions and enables broad access to δ-lactams or piperidines from diverse alkylamine substrates. Cyclohydrocarbonylations accessing lactones are also demonstrated. Increasing catalyst loading enables cyclohydrocarbonylations under an argon atmosphere, using the cobalt carbonyl as both a precatalyst and in situ CO source. The cyclohydrocarbonylations display a surprising dependence on the identity of the cobalt precatalyst, with different reaction outcomes observed using either cobalt carbonyl or KCo(CO)₄. Initial mechanistic and computational studies indicate multiple operative pathways dependent on the catalytic conditions.