2-amino-3-cyano substituted 1,8-naphthyridines has been developed in the presence of starch sulfuric acid (SSA catalyst using aminopyridine, malononitrile, and aromatic aldehydes via Knoevenagel condensation and Michael addition followed by intramolecular cyclization. The SSA catalyst could selectively be converted amino pyridine into 1,8-naphthyridines with good yield in a short period of time at room temperature. This catalyst can be efficiently reused several times without loss of its sustainable activity.
Objectives: Nowadays, antimicrobial resistance represents one of the most significant challenges in the medical community. To overcome the problem, it requires the discovery of newer safe and effective molecules against infectious sickness. Synthesis and screening of 1,8-naphthyridines have attracted much attention over the decades since it plays a key role against the microorganisms.
Methods: 1,8-naphthyridine based 5-arylidene derivatives of thiazolidinone (3a-i) has been achieved by the cyclization reaction of 2-chloro-N- (2-phenyl-1,8-naphthyridin-3-yl)acetamide (1) with potassium thiocyanate in acetone followed by its Knoevenagel condensation reaction with appropriate arylaldehydes in ethanol. All the resulting products were confirmed using spectral and physicochemical data. Antibacterial activity was performed against different bacterial strains by agar disc diffusion method using ciprofloxacin as standard.
Results: Compound 3b showed tremendous antibacterial activity among all the tested compounds.
Conclusions: This study provides several advantages such as shorter reaction times, clean product, and good yields. Most of the final products possessed moderate to excellent antibacterial activity.
In an attempt to discover the new antibacterial agents to fight the bacterial infections, a series of 1,8-naphthyridine based 2-iminothiazolidin-4-one derivatives was synthesized by a straight-forward regioselective synthesis. 2-Phenyl-1,8-naphthyridin-3-amine (2) was reacted with acetyl or aroyl isothiocyantes to give the corresponding N-[(2-phenyl-1,8-naphthyridin-3-yl)carbamothioyl)]acetamide or benzamides (3a-e). Finally, the target compounds [N-(4-oxo-3-(2-phenyl-1,8-naphthyridin-3-yl)thiazolidin-2-ylidene)]acetamide or benzamides (4a-e) were obtained by the reaction of thiourea (3a-e) with chloroacetyl chloride in presence of pyridine. All the synthesized products were formed in good yields and their structures were characterized by spectral (IR, EI-MS and NMR) and physical data. The biological activity of title compounds was evaluated against the bacterial strains and found to be more potent.
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