Abstract Treating 2-mercaptobenzohydrazide (1a) with cyanogen bromide gave 3-amino-2- imino-3, 4-dihydro-2. H-1, 3-benzothiazin-4-one (2a). This compound underwent further cyclocondensation with a second molecule of cyanogen bromide or S-methylisothiourea sulfate to afford the biologically interesting 2-amino-1, 2, 4-triazolo-[5, 1-b][1, 3] benzothiazin- 9-one (3c). Compound 3c could also be prepared directly from 1a by treating with excess ...
