First Approaches for the Novel Pyrido[1'',2'':2',3'][1,2,4]Triazolo [5',1',2,3][1,3]Thiazolo[4,5-b] Pyridines: Synthesis, Characterization and Antimicrobial Efficiency

Vilsmeier–Haack formylation of 3-aminothiazolotriazolopyridine-7,9-dicarbonitrile 3 afforded the corresponding aldehyde derivative 4 in a 65% yield. Some Schiff bases 5-7 were efficiently synthesized by reacting substrate 4 with some primary amines. Reaction of substrate 4 with some active methylene nitriles produced 2-amino-3-substituted-pyridotriazolothiazolopyridines 8–12. Substrate 4 was utilized as a key intermediate for a diversity of pyridotriazolothiazolopyrazolopyridines 13–15, through the Friedlander reaction with pyrazolidine-3,5-dione, 5-amino-2,4-dihydro-3H-pyrazol-3-one, and 5-phenyl-2,4-dihydro-3H-pyrazol-3-one. Further, the reaction of substrate 4 with 5-amino-3-methyl-1H-pyrazole and 6-aminouracil, as cyclic enamines, produced pyridotriazolothiazolopyrazolopyridine 16 and pyridotriazolothiazolopyridopyrimidine 17, respectively. The antimicrobial efficiency was assessed for the synthesized products, and some of them showed notable activity. The structures of the synthesized products were confirmed using analytical and spectroscopic data.