[Et3NH][HSO4]-Catalyzed Efficient, Eco-Friendly, and Sustainable Synthesis of Quinoline Derivatives via Knoevenagel Condensation

An efficient, eco-friendly, and sustainable protocol was described for the synthesis of new quinolinyl alkenes via Knoevenagel condensation of 2-chloro-3-formylquinoline with different active methylene compounds using [Et 3 NH][HSO 4 ] as a catalyst and an environmentally benign solvent eliminating the need for a volatile organic solvent and additional catalyst. This ionic liquid is air and water stable and easy to prepare from amine and acid. Structures of the newly synthesized compounds had been elucidated on the basis of elemental analysis and spectral data (IR, 1 H NMR, 13 C NMR, and mass spectrometry).The ionic liquid was also characterized by 1 H NMR and 13 C NMR. The present methodology is a green protocol as it eliminates the need for a volatile organic solvent and additional catalyst and offers several advantages such as shorter reaction time, excellent yield of products, mild reaction conditions, simple operational procedure, and recyclablility up to seven cycles without any appreciable loss in catalytic activity.