Facile Synthesis of Substituted 2-Styrylnaphthyridine and its Derivatives via sp3 C-H Functionalization under Mild Conditions and their Antimicrobial Activity

Abstract

A simple, metal free strategy is described for the synthesis of substituted 2-styryl-1,8-naphthyridines and pyrazole, imidazopyridine based styryl conjugates under basic mild conditions (piperidine in ethanol) at 70 ºC. The reaction progressed via sp3 C-H functionalization of substituted methyl-1,8-naphthyridines with various aromatic, heteroaromatic aldehyde substrates by Knoevenagel condensation to provides functionalized pyrazole, imidazopyridine based styryl-1,8-naphthyridines in good to excellent yields (85-95%) at impressive reaction time. This approach involves a common organocatalyst, cheap starting materials and shorter reaction times. An extensive variability of substrates was tolerated well to afford the desired products. Furtherly, all the synthesized derivatives were tested for their biological activity, i.e., antibacterial and antifungal. In tested series, compounds 3c, 3d, 3e, 3i, 3k, 3l, 4c, 4d and 4f established excellent inhibition zone of activity against standard drugs.