Visible-light-induced radical cascade reaction to prepare oxindoles via alkyl radical addition to N-arylacryl amides

Herein we describe a photochemical approach towards oxindoles by the radical cascade reaction of alpha,beta-unsaturated N-arylacryl amides with alkyl bromides or iodides upon visible light irradiation. This transition metal- and photosensitizer-free protocol afforded diverse oxindoles with C3 quaternary centers in high product yields under mild reaction conditions. Importantly, the method was applicable to prepare the core skeletons of (+/-)-physovenine, (+/-)-esermethole and (+/-)-physostigmine.