Green chemistry multi-component approach for N-formylation and Knoevenagel condensation for synthesis of thiobarbiturates in aqueous system

A green and efficient method is described for the organic solvent-free synthesis 5-[(arylamino)methylide]-2-thioxodihydropyrimidine-4,6-(1H,5H)-dione derivatives in water has been developed. In this protocol, appropriate amines react with formic acid to afford formamides and in situ formamide derivatives react with the active methylene group of alpha,beta-unsaturated thiobarbituric acid under catalyst-free condition in aqueous medium. Water plays an excellent role in acting as the solvent for both formylation and Knoevenagel condensation reactions. The structures of the product were elucidated by FT-IR, H-1 NMR, C-13 NMR, HMBC, UV-spectra, and elemental analyses. The present protocol offers several advantages such as high yields, mild reaction condition, and easy work-up.