Studies of heterocyclic compounds. Part V. A synthesis of thiothiophthenes and related compounds
Dimethylthioformamide condenses with 3-methyl(ene)-1,2-dithiolium salts in acetic anhydride to give 3-(2-dimethylaminovinyl)-1,2-dithiolium (Vilsmeier) salts. These salts react with sodium hydrogen sulphide to give thiothiophthenes, and with sodium hydroxide to form 3-acylmethylene-3H-1,2-dithioles. H N.m.r. data for these compounds are discussed. An improved procedure for the synthesis of 1,2-dithiolium salts is described.