Visible-light-triggered organophotoredox-catalyzed oxidation of 3-(benzylidine)indoline to indole-3-carbinols and 3-acyl indoles

Abstract

A visible-light-triggered, Eosin-Y-catalyzed oxidative isomerization/carbon–oxygen bond formation of 3-(benzylidine) indolines has been explored to afford structurally diverse indole-3-carbinols and 3-acyl indoles in good-to-excellent yields. This new protocol is metal-free and features mild reaction conditions, easily available starting materials, and environmentally benign reaction conditions. A preliminary mechanistic study reveals that initially, an iminium ion-radical intermediate is formed via a single electron transfer (SET) mechanism, which facilitates cascade isomerization and C–O bond formation through the nucleophilic addition of H₂O.