Efficient Catalytic and Thermal Syntheses of Novel Thiadiazole, Triazole, Benzothiazole, and Fused Quinazoline Derivatives

A thiourea derivative, 4-chloro-N-[(4-chlorophenyl)carbamothioyl]benzamide, was oxidized with iodine in acetic acid to give the corresponding disulfide, whereas its reaction with bromine in acetic acid produced 4-chloro-N-(6-chloro-1,3-benzothiazol-2-yl)benzamide. Thiadiazole derivative was obtained as a result of chlorination of the thiourea, followed by amination and subsequent intramolecular cyclodehydration. Triazole derivative was synthesized by the condensation of that thiourea with 2 equiv of hydrazine hydrate in ethanol. The thiourea derivative underwent cyclization on heating in N,N-dimethylformamide to generate intermediate 6-chloro-4-(chlorophenyl)quinazoline-2(1H)-thione which reacted with nitrogen and carbon nucleophiles such as semicarbazide, thiosemicarbazide, urea, diethyl succinate, and diethyl malonate to afford fused triazoloquinazoline, pyroloquinazoline, and some other quinazoline derivatives.