Some 3-(1,2,3-thiadiazol-4-yl) coumarins (III) have been prepared from 3-acetyl coumarin semicarbazones (II) by treating the latter with thionyl chloride. Compounds II are obtained by interaction of 3-acetyl coumarins (I) with semicarbazide hydrochloride in pyridine. Certain condensed heterocycles such as 3-(6-hydroxythiazolo[3,2-a] benzimidazol-3-yl) coumarins (V) have also been prepared from condensation of 3-(2-amino-4-thiazolyl) coumarins with p-benzoquinone. The structures of these compounds have been established by elemental analysis and spectral data.