l-Proline-catalyzed multicomponent synthesis of 3-indole derivatives

A green one-pot multicomponent reaction for the synthesis of 3-indole derivatives was developed via l-proline-catalyzed condensation between indoles, aldehydes, and malononitrile. The process was carried out in ethanol at room temperature, and the desired products were obtained in good to excellent yields of up to 98%. Pyrrole as the nucleophile and 2,2,2-trifluoroacetophenone as the electrophile can also work in this transformation. The salient features of this protocol were environmental friendliness, simplicity of the procedure, ready accessibility of the catalyst, high yield, and mild reaction conditions.