Synthesis of 2,1,3-benzothiadiazolecarbonitriles

2,1,3-Benzothiadiazolecarbonitriles, 2 , have been prepared by two different methods. Reaction of bromo-2,1,3-benzothiadiazoles, 1 , with cuprous cyanide occurs advantageously in refluxing dimethylformamide to give 2 , complexed with curpous bromide. Hydrogen peroxide in hydrochloric acid at 30–40° is shown to be an effective reagent for efficient decomposition of these reactions complexes, 2 CuBr, and subsequent isolation of 2. Yields in the Sandmeyer method for preparing nitriles 2 were improved by diazotizing amino-2,1,3-benzothiadiazoles, 3 , with nitrosyl-sulfuric acid prior to reaction with the cuprous-sodium cyanide complex.