Deep eutectic solvent: An efficient and green catalyst for the three-component condensation of indoles, aromatic aldehydes, and activated methylene compounds

The deep eutectic solvent-catalyzed multicomponent reaction of aldehydes, indoles, and activated methylene compounds under sonication has been developed. The method proceeded well for a wide scope of substrates under mild condition to afford 3-substituted indoles in moderate to good yields. Interestingly, no additives or solvents are used for the protocol. Moreover, the deep eutectic solvent (zinc chloride and choline chloride) is an inexpensive and recyclable catalyst making the protocol more efficient, facile, and cost-effective. (C) 2019 Elsevier Ltd. All rights reserved.