A convenient one pot preparation of 4-thiazolidinones from enaminolactones

Enaminones 3 and 4, precursors of 4-thiazolidinones, were prepared by condensing tetronic acid (1a) and 4-hydroxy 6-methyl pyrone (1b) respectively with thiosemicarbazide derivatives 2 in refluxing ethanol. The 4-thiazolidinones 6, 7 derivatives were obtained by reacting compounds 3 or 4 with ethyl 2- bromo propionate 5 in the presence of anhydrous sodium acetate in ethalonic medium. Similarly, 9 products were synthesized by action of benzyl 2-bromo acetate 8 on 3.