V. G. Pesin, V. Sergeev, B. Mirkin
1969
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Journal
Chemistry of Heterocyclic Compounds
Abstract
Benzo-2, 1, 3-thiadiazole and its 4- and 5-methyl and 5, 6-dimethyl derivatives are oxidized by chromic anhydride in sulfuric acid to 2, 1, 3-thiadiazole-4, 5-dicarboxylic acid (I) in maximum yield at 80° C. Below or above 80° C, the yield of I falls. At the same temperature, the methyl derivatives are converted into acid I in lower yield than benzo-2, 1, 3-thiadiazole. When I is heated in nitrobenzene at 160° C, an 80% yield of 2, 1, 3-thiadiazole-4-carboxylic acid is formed.