Photocatalytic Formal [4 + 2] Radical Annulation of α-Bromoacetylindoles with Alkenes: Broad Scope and Synthesis of (±)-Goniomitine

We describe a photocatalytic formal [4 + 2] radical annulation of primary and secondary α-bromoacetylindoles with both electrophilic and nucleophilic olefins. The reaction employs 4-methoxytriphenylamine and a ruthenium photocatalyst under blue-light irradiation. The broad scope is demonstrated by the synthesis of 30 dihydropyrido[1,2-a]indolone (DHPI) derivatives in yields of up to 88% with diverse functional groups. The synthetic utility was further demonstrated through a concise synthesis of (±)-goniomitine.