Studies of heterocyclic compounds. Part VIII. Direct conversion of 4H-thiopyran-4-thiones into 6a-thiathiophthens and 3-acylmethylene-3H-1,2-dithioles

Abstract

4H-Thiopyran-4-thiones are ring-opened by sulphide or hydroxide in dimethyl sulphoxide or NN-dimethylformamide, forming anions which undergo intramolecular oxidative coupling to give 6a-thiathiophthens or 3-acylmethylene-3H-1,2-dithioles, respectively. The procedure provides a useful synthesis of 6a-thiathiophthen.