One-pot synthesis of 3-substituted indole derivatives using moisture stable, reusable, and task specific ionic liquid catalysts

Abstract

Moisture stable Brönsted acidic (BIL) and Lewis acidic ionic liquid catalysts have been synthesized and their catalytic activities have been examined in the synthesis of biologically important indole-3-derivatives. Catalytic activities of these ionic liquid catalysts have been investigated for some important catalytic reactions such as three component coupling reaction of benzaldehyde, N-methylaniline and indole and Michael addition reaction of indole with β- nitrostyrene/chalcone/acetyl acetone. In all these reactions, BIL functionalized with sulfonic acid is found to be the best task specific catalyst. BILs are inexpensive and easy to synthesize, and can be separated easily and reused for three cycles without significant loss in catalytic activity. Catalyst offers several attractive features such as low cost, high catalytic activity/selectivity and recyclability.