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.