C3 Alkylation of Indoles Catalyzed by Carbocations under Continuous-Flow Conditions

A fast and practical protocol for the C3 alkylation of varied indole substrates catalyzed by carbocations was developed under continuous-flow conditions. Because of the enhanced mass- and heat-transfer features of the microreactor, the reaction time was significantly reduced compared with batch conditions. The functional group tolerance of this method is good, the substrate scope for indoles and α,β-unsaturated carbonyls is broad. In addition, the reactants were employed in the ratio of 1:1 to achieve good to excellent yields. It is an effective reaction to cut down chemical waste and is of benefit for environment protection from an industrial production point of view.