Regioselective Synthesis of Novel [N-(4-Oxo-3-(2-phenyl-1,8-naphthyridin-3-yl)-thiazolidin-2-ylidene)]acetamide/benzamides and their Biological 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.