A Facile Synthesis and Antibacterial Activity of Novel Quinoxaline-Benzofuran Hybrids

In the present work, a simple and facile synthesis of a series of new type of quinoxaline-benzofuran hybrids, i.e., 3-(benzofuran-2-yl)quinoxaline-2-carboxylic acids has been achieved using the newly-synthesized ethyl 3-bromomethylquinoxaline-2-carboxylate as substrate through ultrasound-assisted one-pot sequential Rap-Stoermer type reaction with various salicylaldehydes followed by ester hydrolysis.A preliminary screening for their antibacterial activities against five bacterial strains revealed that compounds with tert-butyl and halo (Cl and Br) substituents exhibited promising inhibitory activity against B. subtilis with the MIC values of 15.625 and 7.8125 μg/mL, respectively, being equipotent or even better than the reference Ciprofoxacin.Among nitrogen-containing heterocycles, quinoxaline ring is an important structural motif present as pivotal skeleton in numerous significant natural products and pharmacologically relevant compounds with significant biological properties such as anticancer, 1 antimycobacterial 2 and antibacterial activities. 36][7] Especially, in recent years the synthesis and antibacterial activity evaluation of various quinoxaline-heterocycle hybrids have frequently been reported for current antibacterial drug studies.For example, Kamila et al. 8 reported an easy access to novel series of quinoxaline-indole hybrids, which exhibited important antibacterial activity.Recently,