Bromination of 2,1,3‐benzothiadiazoles

Abstract The bromination of 2,1,3‐benzothiadiazoles in 47% hydrobromic acid at elevated temperature has led to a general preparative method for the synthesis in high yield of otherwise difficulty accessible brominated 2,1,3‐benzothiadiazoles. The typical addition reaction is apparently eliminated under these reaction conditions and substitution takes place exclusively. Bromination of 2,1,3‐benzothiadiazole occurs successively at positions 4 and 7. 4‐Substituted 2,1,3‐benzothia‐diazoles are selectively brominated at position 7. 5‐Bromo‐ and 5‐methyl‐2,1,3‐benzothiadiazole are brominated consecutively at positions 4 and 7.