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

Abstract

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.