Design, synthesis and antimicrobial activity of heteroannulated chromeno[3′,2′:5,6]pyrido[2,3-d][1,3]thiazolo[3,2-a]pyrimidines

The current research is directed to construct a novel category of linear annulated chromeno[3`,2`:5,6]pyrido[2,3-d][1,3]thiazolo[3,2-a]pyrimidines. The chemical reactivity of the recently synthesized aldehyde 1 was examined toward a diversity cyclic methylene ketones, cyclic enamines and cyclic enols. Friedländer condensation of aldehyde 1 with 1,3-cyclohexanediones gave the multi-linear chromenopyrido- pyrimidothiazoloquinolines 2 and 3. Also, treating aldehyde 1 with some pyrazolones furnished annulated chromenopyridopyrazolopyridothiazolopyrimidines 4-6. Further, 1,3-thiazolidine-2,4-dione and barbituric acid condensed with aldehyde 1 giving chromenopyridothiazolopyridothiazolopyrimidine 7 and chromenopyridopyrimido-thiazolopyridopyrimidine 8, respectively. Moreover, reacting aldehyde 1 with cyclic enamines (6-amino-2-thiouracil and 6-amino-1,3-dimethyluracil) and cyclic enols (4-hydroxycoumarin and 1-ethyl-4-hydroxyquinolin-2(1H)-one) furnished polyfused heterocycles 9-12, respectively. During in vitro investigation of the antimicrobial efficiency, the synthesized compounds showed considerable activity against yeast and fungal strains, as well as moderate to high activity against Gram-positive and Gram-negative bacteria. Polyfused compounds 4-6 showed significant efficiency against all types of tested microorganisms.