A number of 6-(m-tolylazo)-thiazolo[3,2-a]pyrimidine-3,5,7(2H)-trione (3), 2,6-di(m-tolylazo)thiazolo[3,2-a]pyrimidine-3,5,7(2H)-trione (4), thiazolo[3,2-a]pyrimidine-3,5,7-trione (5) and 2-(m-tolylazo)thiazolo[3,2-a]pyrimidine-3,5,7(2H)-trione (6) here been prepared. The structure of the new ring system have been confirmed by IR and 1H-NMR spectral data.