Novel heteroannulated chromeno[3′,2′:5,6]pyrido[2,3-d]pyrido[2′,3′: 4,5][1,3]thiazolo[3,2-a]pyrimidines: synthesis, characterization and antimicrobial evaluation

Abstract

The main aim of the current research is directed to find a suitable approach to construct a new annulated systems namely chromeno[3′,2′:5,6]pyrido[2,3-d]pyrido[2′,3′:4,5][1,3] thiazolo[3,2-a]pyrimidines. Treatment of 3-cyano-6,8-dimethylchromone with thiobarbituric acid gave chromeno[3′,2′:5,6]pyrido[2,3-d]pyrimidine, which upon treatment with chloroacetonitrile afforded 3-aminochromenopyridothiazolopyrimidine. Vilsmeier Haack formylation of the later compound produced the desired o-aminocarboxaldehyde derivative 4. Condensation of compound 4 with some active methylene nitriles namely malononitrile, cyanoacetamide, ethyl cyanoacetate, cyanoacetamide, N-phenyl-2-cyanoacetamide, 1H-benzimidazol-2-ylacetonitrile, and malononitrile dimer produced annulated compounds 5–10 (64–76% yields). Friedländer condensation of compound 4 with some active methylene ketones namely acetylacetone, ethyl cyanoacetate, diethyl malonate, and acetoacetanilide afforded annulated systems 12–15 (65–71% yields). During in vitro examination of the prepared compounds against antimicrobial activity, they appeared high activity against yeast, fungus strains and intermediate activity against all types of bacterial strains. The poly-functional product 10 exhibited notable efficiency against all types of the used microorganisms, while compound 4 present high activity against Gram-positive, yeast and fungus strains. Using spectral and analytical data, the structures of the newly synthesized products were inferred.