Radical Relay Meets Migration: TBADT-Catalyzed Access to 3,3-Disubstituted Oxindoles via Alkyl/Aryl Shift

Abstract

Herein, we report a hitherto unexplored light-induced radical cascade process for the synthesis of oxindole frameworks using tetrabutylammonium decatungstate (TBADT), a well-known hydrogen-atom-transfer (HAT) photocatalyst. This cascade photochemical transformation proceeds via an unprecedented intermolecular radical addition, an intramolecular ring closure, and a 1,2-alkyl/aryl shift. Notably, this process is highly atom-economic; the initial acyl C–H activation is feasible under mild conditions without the use of additives or external reagents. The strategy is compatible with various aldehydes and diverse N-(2-ethynylaryl)amides, delivering structurally diverse 3,3-disubstituted oxindoles, including structurally diverse drug derivatives and other synthetic extensions.