One-Pot Three-Component Synthesis of 2-Imino-1,3-Thiazolines on Soluble Ionic Liquid Support

An efficient one-pot, three-component synthesis of 2-imino-1,3-thiazolidines and 2-imino-1,3-thiazolines using ionic liquid-tethered 2-aminobenzimidazoles was reported. The protocol includes reaction of ionic liquid attached 2-aminobenzimidazoles with isothiocyanates to afford isothioureas, followed by its base induced inter and intramolecular nucleophilic displacement reactions with 1,2-dichloroethane (EDC) which results in thiazolidine ring formation. In the next to the last step, the ionic liquid support was removed by methanolysis to deliver 2-imino-1,3-thiazolidines, which were sequentially oxidized with manganese(III) triacetate to yield 2-imino-1,3-thiazolines. The salient feature of this method is the use of 1,2-dichloroethane as a synthetic equivalent for α-haloketone to avoid the use of toxic halogenating reagents.