Reductive sulfur extrusion reaction of 2,1,3-benzothiadiazole compounds: a new methodology using NaBH4/CoCl2·6H2O(cat) as the reducing system

A new simple and efficient methodology for reductive sulfur extrusion from 2,1,3-benzothiadiazole compounds has been developed using NaBH4 in the presence of catalytic amounts of CoCl2·6H2O (1 mol %). This method is an efficient alternative for the generation of various 1,4-disubstituted-2,3-diaminobenzene derivatives from 4,7-disubstituted-2,1,3-benzothiadiazoles. The diamines can be easily converted into 4,7-disubstituted-quinoxaline compounds by simple reaction with glyoxal–sodium bisulfite.