Photoenolization/nucleophilic addition enables direct access to 3-alkyl-3-hydroxy-indolin-2-ones

A light-driven, catalyst- and additive-free photoenolization/nucleophilic addition reaction for the synthesis of 3-benzyl-3-hydroxyindolin-2-ones is presented. In this reaction, 2-methylbenzophenones undergo light-induced enolization process to afford hydroxy-o-quinodimethanes (hydroxy-o-QDMs), which are then immediately captured by the electrophilic isatins. The reaction utilizes green and clean light energy to realize the C–H activation of the inert benzyl position of 2-methylbenzophenones. This method tolerates a wide scope of substrates and provides concise access to a series of novel 3-benzyl-3-hydroxyindolin-2-ones with 60–99% yields.