Abstract α, β-Unsaturated acyl isothiocyanates react with N-methylaniline to give thioureas which, when treated with bromine in chloroform, afford benzothiazoline derivatives. Under the same reaction conditions primary amines, diethylamine, piperidine and morpholine furnish 2-substituted 5-arylidenethiazolin-4-ones. Their structure was corroborated by an independent synthesis and on the basis of spectral (IR, 1 H-NMR and mass) evidence.