Diastereoselective Access to Tetracyclic Eight‐Membered Lactams through a Dearomative Heck Reaction and an Alkylative Ring‐Opening Driven by Photoexcited Spiroindolines

An external‐photocatalyst‐free, light‐driven alkylative ring‐opening of stable spiroindolines was developed to construct indolo‐ and benzoannulated eight‐membered lactams. The spiroindolines were prepared from tetrahydro‐β‐carbolines by a dearomative Heck reaction. Mechanistic experimental studies on the alkylative ring opening suggested that a photoredox pathway was involved, in which the spiroindoline performed as both reagent and photosensitizer. DFT calculations showed that the radical addition toward a cyclic alkene was the key to the diastereoselective formation of tetracyclic medium‐sized lactams. Get (photo)excited! A light‐driven alkylative ring‐opening of spiroindolines with complete diastereoselectivity is developed to construct indolo‐ and benzoannulated eight‐membered lactams, in which the spiroindoline performs as both reagent and photocatalyst.