The Synthesis of the New 1,4,2-Dithiazine Ring

Abstract
Some derivatives of N-(2-phenylethene-l-sulfonyl)-N′-alkylthioureas of the R1C6H4CH=CHSO2NHCSNHR2 2 type were synthesized by a reaction between 2-phenylethene-l-sulfonamides 1 and isothiocyanates in acetone in the presence of K2CO3. A new heterocyclic system, 3-alkylamino-5-phenyl-1,1-dioxo-5,6-dihydro-l,4,2-dithiazine 3, was obtained by the intramolecular Michael cycloaddition of 2 in weakly basic media, and also by the thermal cyclization of 2. The carbon-sulfur bond in 3 could be cleaved to give 2 again in strongly basic media.

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