Choline based deep eutectic solvent mediated Friedlander annulation: A sustainable and regiospecific approach to polysubstituted quinoline

Abstract

Polysubstituted quinolines have been synthesized by Friedlander annulation reaction of 2-aminobenzophenone with ketones mediated by choline-based deep eutectic solvents (DESs). We have investigated the condensation reaction in different choline-based DES and found choline chloride-zinc chloride DES to be the best catalyst with excellent yield of products. Moreover, regiospecificity was observed only under basic choline hydroxide medium in moderate yield. The deep eutectic solvent acts as dual role of solvent as well as catalyst and can be recycled. Mild reaction conditions, simple work-up procedure, excellent product yield, and use of recyclable catalyst are special features of this methodology, which makes the protocol a sustainable alternative to earlier reported methods of quinoline synthesis.

Keywords

• Choline chloride
• Deep eutectic solvent
• Quinoline
• Friedlander reaction
• Regiospecificity