1. Phosgenation of methyl anthranilate
2. Synthesis of 3,4-dihydro-1H-1,3,4-benzotriazepine-2,5-diones
3. Alkylation and ring contraction reactions of 1,3,4-benzotriazepine-2,5-dione systems
4. A rearrangement analogous to that of 2 to 3, employing vigorous conditions of acid-catalysis, has been reported by Howard and Klein (6). Thus, treatment of 2-[(1-aziridinylthiocarbonyl)amino]benzoic acid methyl ester (i) with concentrated hydrochloric acid at reflux produced 2,3-dihydro-5H-thiazolo[2,3-b]quinazolin-5-one (ii).