Synthesis of Biginelli products of thiobarbituric acids and their antimicrobial activity

A simple and efficient method has been developed for the synthesis of 2,4,7-tri(substituted)phenyl-2,4,8,10-tetraza-3,9-dithioxo-5-oxobicyclo[4.4.0]dec-1(6)-ene (4) and 2,4,7-tri(substituted)phenyl-2,4,8,10-tetraza-3-thioxo-5,9-dioxobicyclo[4.4.0]dec-1(6)-ene (5), by a one-pot, three-component cyclocondensation reaction of a 1,3 dicarbonyl compound (thiobarbituric acid), an aromatic aldehyde, and urea/thiourea using catalytic a amount of concentrated HCl in refluxing ethanol. Representative samples were screened for their anti-microbial activity against the Gram-negative bacteria, Escherichia coli and Proteus aeruginosa, and the Gram-positive bacteria, Staphyllococcus aureus and Corynebacterium diphtheriae using the disc diffusion method. The structures of the products were confirmed by IR, 1H- and 13C-NMR spectroscopy, as well as by elemental analysis