Reactions of 2‐aminothiobenzamide with isocyanates: A new synthesis of 2, 3‐dihydroimidazo[1, 2‐c]quinazolin‐5(6H)‐one and 3, 4‐Dihydro‐2H‐pyrimido[1, 2‐c]quinazolin‐6(7H)‐one

Abstract 2‐(2‐Chloroethylureido)‐ and 2‐(3‐chloropropylureido)thiobenzamides 5a, b were prepared in good yields by treating 2‐aminothiobenzamide with 2‐chloroethyl and 3‐chloropropyl isocyanates respectively. Subsequent treatment of compound 5a and 5b either with alkali or mineral acid led to the formation of 2, 3‐dihydro‐imidazo[1, 2‐c]quinazolin‐5(6H)‐one 7a and 3, 4‐Dihydro‐2H‐pyrimido[1, 2‐c]quinazolin‐6(7H)‐one 7b.