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.