Facile synthesis of thiadiazolo [2,3-b] quinazoline derivatives via the Japp-Klingemann Reaction

Diazotized anathranilic acid and its methyl ester react with substituted α-thiocyanatoacetoacetanilides3a–c to give in both cases the corresponding thiadiazolo [2,3-b] quinazolines6a–c, respectively. A mechanism is proposed and it is substantiated by synthesis of6a from N-(2-car?yphenyl)-C-phenylcarbamoyl hydrazidoyl chloride8a or its N-(2-methoxycarbonylcarbonylphenyl) analogue8d.