1, 2, 3-Tribromopyrrolo [1, 2-b][1, 2] benzothiazin-10-one (2) is produced from 2-[2- (benzylthio) benzoyl] pyrrole (1) when treated with excess (5 equiv) NBS in CHCl3. With NCS, a mixture is obtained in which di-and trichloropyrrolo [1, 2-b][1, 2] benzothiazin-10- ones are present. If ethanol is present in the NCS reaction, compound 4 is formed as the major product. Further, compound 3 is also formed by the reaction of compound 1 or the ...