Certain (2E)-substituted-2-ethylidene-5, 6-diphenylimidazo[2, 1-b][1, 3]thiazol-3-(2H)-ones (4a-f) have been synthesized by the condensation of 4, 5-diphenylimidazoin-2-thiones (3) with different aromatic aldehydes and chloroacetic acid in presence of acetic anhydride, anhydrous sodium acetate and glacial acetic acid. These compounds were characterized by their analytical and spectral data. The title compounds were found to be efficient antibacterial agents on evaluation. © 2014 Elsevier B.V., All rights reserved.