3-Methyl-1-sulfoimidazolium ionic liquids as recyclable medium for efficient synthesis of quinoline derivatives by Friedländer annulation

Abstract

Two acidic ionic liquids, 3-methyl-1-sulfoimidazolium trichloroacetate ([Msim][OOCCCl3]) and 3-methyl-1-sulfoimidazolium chloride ([Msim]Cl) were efficiently utilized as recyclable acidic homogeneous medium for the Friedlander synthesis of quinolines at 100 °C. The reaction completed with single product formation in short time and involved simple isolation of product with 95–100 % yields. The novel ionic liquids [Msim][OOCCCl3] and 1-methylimidazolium trichloroacetate ([Hmim][OOCCCl3]) prepared from CCl3COOH were fully characterized by various analytical techniques. The catalytic activity of the more acidic ionic liquids was also compared with the CCl3COOH acid catalyzed synthesis of quinoline at 100 °C under solvent-free condition.