Properties of 2,1,3-Benzothiadiazoles

The bromination of melted 2,1,3-benzothiadiazole in the presence of reduced iron powder provides an improved procedure for the exclusive production of the 4,5,6,7-tetrabromo-derivative, in 53% yield. Sulphona-tion of 7-bromo-2,l,3-benzothiadiazole yields the 4-sulphonic acid (233), 

Tobiason, L. Huestis, C. Chandler, S. E. Pedersen, and P. Peters, J. Heterocyclic Chem., 

Examples of the production of 2,1,3-benzoselenadiazoles (235) from o-diamines, e.g. (234 X = H or Br), by the action of selenium dioxide have been described.  

Benzoselenadiazoles are aminated by treatment with equimolar quantities of hydroxylamine sulphate in concentrated sulphuric acid in the presence of vanadium pentoxide as catalyst the appropriate amines, e.g. (236), are isolated in moderate yields (9—37%).  

---