N-heterocyclic nitrenium-catalyzed photosynthesis of 3,3-disubstituted oxindoles from α-chloroanilides.

The radical cascade reaction of α-halogenated anilides represents an efficient approach for synthesizing 3,3-oxindoles. However, most methods have focused on α-bromoanilides, with limited utilization of the more stable and readily available α-chloroanilides. In addition, the transition-metal-free preparation of 3,3-oxindoles has been far less explored. Here, we present a photoreductive N-heterocyclic nitrenium-catalyzed radical cyclization reaction of α-chloroanilides for the construction of 3,3-oxindoles under transition-metal-free conditions.