Reactions of Dimethyl Acetylenedicarboxylate with 2,5-Dithiobiurea Derivatives

Abstract

Symmetrically and unsymmetrically N 1 ,N 2 -disubstituted hydrazine-1,2-dicarbothioamides (2,5-dithiobiureas) react with dimethyl acetylenedicarboxylate in refluxing ethanol to give dimethyl 2,2′-[2,2′-(hydrazine-1,2-diylidene)bis(3-aryl/alkyl-4-oxothiazolidine-5,2-diylidene)diacetate and methyl 2-(2-{[5-(2-methoxy-2-oxoethylidene)-4-oxothiazolidin-2-ylidene]hydrazono}-4-oxothiazolidin-5-ylidene)acetate derivatives and N 2 ,N 5 -disubstituted 1,3,4-thiadiazole-2,5-diamines. The structure of one product has been confirmed by a single-crystal X-ray structure analysis. A rationale for the formation of the products is presented.