Addition products of benzimidazole-2 (2H)-thione and acetylene dicarboxylic esters☆

This chapter discusses the synthesis of 4-Thiazolidinones. The synthesis of condensed 4-thiazolidinones can be achieved using the cyclization procedure involving the 2- and 3-Positions of 4-thiazolidinone, the 2- and 5- positions of 4-thiazolidinone, and the 2,3- and 2,5-positions of 4-thiazolidinone. The molecular spectra of condensed 4-thiazolidinones are also discussed. Infrared spectra of condensed 4-thiazolidinones have been reported by numerous workers and display structurally and diagnostically useful features. A single crystal X-ray study of one of the products obtained from the reaction of benzimidazolyl-2-thione with DMAD confirms the thiazolidinone structure, which was earlier tentatively assigned on the basis of chemical evidence. The methylene carbon atom in a condensed 4-thiazolidinone flanked by a sulfur atom and a carbonyl group possesses enhanced nucleophilic activity and attacks an electrophilic center with ease. If the structure permits, the reaction product loses a molecule of water, and an unsaturated derivative is formed. The reaction is carried out in the presence of a base which abstracts a methylene proton. Condensed 4-thiazolidinones have been shown to exhibit antifungal, antibacterial, anticonvulsant, and anti-inflammatory activities.