A simple construction of 2-phenylimino-1,3-thiazolidin-4-ones

A new methodology for the construction of 2-phenylimino-1,3-thiazolidin-4-o ne skeleton is described. Reaction of maleic anhydride (5a) or maleimides ( 5b, 5c) with thiourea (6) gave the corresponding 2-imino-1,3-thiazolidin-4- ones (7) and (9) respectively. The reaction proceeded with high yield in po lar solvents. In non-polar solvents at high temperature, however, isothiocy anate (8) was formed as a by-product presumably by the pyrolysis of thioure a (6). The proposed mechanism of the reaction was discussed.