Synthesis of novel pyrido[2,1-b]benzothiazole and N-substituted 2-pyridylbenzothiazole derivatives showing remarkable fluorescence and biological activities

Abstract

Abstract The synthesis of novel pyrido[2,1-b]benzothiazole and pyrido[2,1-b]benzoimidazole derivatives was achieved via the reaction of N-aryl-2-cyano-3,3-bis(methylthio)acrylamide with benzothiazoleylacetonitrile and benzoimidazoleylacetonitrile, respectively, while N-substituted 2-pyridylbenzothiazole derivatives were synthesized by reacting 2-(benzo[d]thiazol-2-yl)-3-(dimethylamino)acrylonitrile with either cyanoacetamide, aryl cyanoacetamides or 2-cyano-N’-(4-substituted benzylidene)acetohydrazide. Based on the steady state fluorescence measurements, the newly synthesized N-substituted 2-pyridylbenzothiazole derivatives exhibited remarkable fluorescence properties with considerably high quantum yields (0.25–0.29). In addition, the antimicrobial and antiviral activities were evaluated for all the newly synthesized derivatives. The antimicrobial examination revealed that triazolo-pyridone 21a had the highest potency among all tested compounds against Escherichia coli, Klebsiella pneumonia and Staphylococcus aureus while pyrido[2,1-b]benzoimidazole derivatives 9a and 9b had the highest potency over other compounds against Candida albicans fungus.