Visible Light‐Induced Umpolung Synthesis of 3,3‐Disubstituted Oxindoles via the Substrate‐Photosensitive Strategy

Comprehensive Summary 3,3‐Disubstituted oxindoles, forming the core of extensive bioactive natural products and drugs, attract tremendous efforts to develop efficient methods for their preparation. Here, a photocatalyst‐free approach for the synthesis of 3,3‐disubstituted oxindoles via a substrate‐photosensitive strategy under visible light was successfully developed. Preliminary mechanistic studies illustrated that isatin‐derived imines can be directly excited by visible light to generate strong oxidant states, facilitating subsequent single‐electron transfer (SET) processes with Hantzsch esters to afford the corresponding α‐amino radical intermediates. Thus, these α‐amino radicals promote the subsequent Giese radical addition or radical/radical cross‐coupling reactions to furnish diverse functionalized 3‐substituted 3‐aminooxindoles in high yields.