Synthetic Utilization of Polynitroaromatic Compounds. 2. Synthesis of 4,6-Dinitro-1,2-benzisothiazol-3-ones and 4,6-Dinitro-1,2-benzisothiazoles from 2-Benzylthio-4,6-dinitrobenzamides

Cyclization of 2-benzylthio-4,6-dinitrobenzamides to 4,6-dinitro-1,2-benzisothiazol-3-ones was achieved using SO2Cl2 in CH2Cl2 at room temperature. Alkylation of these heterocycles proceeded in a nonregioselective manner to yield a mixture of corresponding O- and N-alkylated products. Oxidation of 4,6-dinitro-1,2-benzisothiazoles (50% H2O2 in AcOH) afforded the corresponding S-oxides and S,S-dioxides, depending on oxidation conditions. Unexpectedly, oxidation of a 3-methoxy derivative resulted in ring opening with the formation of the corresponding sulfamide. Chlorination of these 4,6-dinitro-1,2-benzisothiazol-3-ones (PCl5−POCl3) gave the expected 3-chloroisothiazoles.