nilines 1a,b with carbon disulfide in the presence of potassium t-butoxide in boiling DMF afforded the corresponding benzimidazo[1,2-c]quinazoline-6(5H)-thiones 2a,b. Treatment of these compounds with hydrazine hydrate at reflux in ethanol gave the hydrazine derivatives 3a,b which were subsequently cyclised to the title compounds 4a–f on heating with orthoesters in ethanol.