Design, synthesis and biological evaluation of novel chalcone-derived thioxopyridine and pyrazolopyridine compounds as antimicrobial agents.

The present work deals with the synthesis of some new chalcone, 2- thioxopyridine,2-methylthiopyridine, 2-hydrazinopyridine and 3-amino-1H-pyrazolo[3,4-b]pyridine derivatives containing biologically active substituents. The starting material of the present study was synthesis of the 2-cyanoethanethioamide from malononitrile using a modified Brunskill procedure, followed by the synthesis of the 1,3-diarylprop-2-en-1-one (chalcone) from a ketone and an aldehyde. 2-Thioxopyridines were obtained through Michael addition of α,β-unsaturated ketones with 2-cyanothioacetamide to afford the non-isolable intermediates 8 & 9 followed by cyclization and subsequent dehydration and dehydrogenation of the cyclized product to give compound 4-(furan-2-yl)-6-(4- methoxyphenyl)-2-thioxo-1,2-dihydropyridine-3-carbonitrile which was reacted with methyl iodide in methanolic sodium methoxide to afford the corresponding 4-(furan-2-yl)-6-(4-methoxyphenyl)-2-(methylthio) pyridine-3-carbonitrile, which was reacted with hydrazine hydrate to give the corresponding 2-hydrazinopyridines, which cyclized to afford the corresponding 3-aminopyrazolo[3,4-b]pyridine derivatives and were characterized by FT-IR,