Synthetic utilization of polynitroaromatic compounds. 2. Synthesis of 4,6-dinitro-1,2-benzisothiazol-3-ones and 4,6-dinitro-1,2-benzisothiazoles from2-benzylthio-4,6-dinitrobenzamides

Cyclization of 2-benzylthio-4,6-dinitrobenzamides to 4,6-dinitro-1,2-benzis othiazol-3-ones was achieved using SO2Cl2 in CH2Cl2 at room temperature. Al kylation of these heterocycles proceeded in a nonregioselective manner to y ield st mixture of corresponding O- and N-alkylated products. Oxidation of 4,6-dinitro-1,2-benzisothiazoles (50% H2O2 in AcOH) afforded the correspond ing S-oxides ana S,S-dioxides, depending on oxidation conditions. Unexpecte dly, oxidation of a 3-methoxy derivative resulted iri: ring opening with th e formation of the corresponding sulfamide, Chlorination of these 4,6-dinit ro-1,2-benzisothiazol-3-ones (PCl5-POCl3) gave the expected 3-chloroisothia zoles.