SYNTHESIS AND ANTIBACTERIAL SURVEY OF SOME NEW PYRIDINE-BASED HETEROCYCLES

Treatment of ethyl 2-((3-cyano-4,6-dimethylpyridin-2-yl)thio)acetate (4) with hydrazine hydrate furnished 2-((3-cyano-4,6-dimethylpyridin-2-yl)thio)acetohydrazide (5) which underwent condensation with five benzaldehydes to afford the corresponding N'-arylidene-24(3-cyano-4,6-dimethylpyridin-2-ypthio)acetohydrazides 6a-e. The reaction of hydrazide 5 with ethyl acetoacetate yielded the expected 2((2-(3-methyl-5-oxo-pyrazolyl)-2-oxoethyl)thio)nicotinonitrile derivative 7 which diazo-coupled with different diazonium chlorides to furnish the corresponding 2-(4-(2-arylhydrazono)pyrazolyl)-2-oxoethyl)thio)nicotinonitriles 8a-c. In addition, the nucleophilic substitution of chlorine from 2-chloroacetamide derivative 16 by various types of nucleophiles (salicylaldehyde, ethyl thioglycolate, 2-mercaptobenzoxazole, ammonium thiocyanate and/or malononitrile) was investigated. In general, all synthesized pyridine scaffolds revealed better activity against the Gram-positive bacterium (Bacillus subtilis) rather than the Gram-negative bacterium (Escherichia coli).