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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. [ABSTRACT FROM AUTHOR]

The essential aim of the present study is designed to utilize 4,9-dimethoxy-5-oxo-5H-furo[3,2-g]chromene-6-carbonitrile (1) to build some novel heterocyclic systems containing benzofurans as well as furo[3,2-g]chromenes. Ring opening ring closure reactions of compound 1 with N-phenyl-2-cyanoacetamide produced 8-amino-furochromenopyridine-7-carboxamide 2, which cyclized with some electrophilic reagents giving furochromenopyridopyrimidines (63–73% yields). The reaction of carbonitrile 1 with pyrazolone derivatives yielded furochromenopyrazolopyridines 10 and 11 in good yields. Also, benzo[h]furochromeno naphthyridine 13 was synthesized from recyclization of carbonitrile 1 with 1-ethyl-4-hydroxyquinolin-2(1H)-one (12). On a different mechanism, recyclization of carbonitrile 1 with some 1,3-binucleophiles afforded pyrido[2,3-d]pyrimidines (14 and 15), pyrimido[1,2-a]pyrimidine 17 and pyrimido[2,1-c][1,2,4]triazine 19 in suitable yields (62–71%). Finally, the reaction of carbonitrile 1 with 1,3-cyclohexanedione and 1,4-cyclohexanedione in 2:1 molar ratio yielded polyfused systems 20 and 21, respectively. Based on spectral and analytical results, the structures of the all products were inferred. [ABSTRACT FROM AUTHOR]

The chemical reactivity of 2-methylchromone-3-carbonitrile (1) was investigated toward a diversity of active methylene nucleophiles. Ring-opening followed by recyclization reactions of compound 1 with some active methylene nitriles afforded 2-amino-3-substituted-4-methylchromeno[2,3-b]pyridin-5-ones. Also, reactions of carbonitrile 1 with some active methylene ketones produced 2,4-dimethylchromeno [2,3-b]pyridin-5-ones. Annulated chromeno[2,3-b]pyrazolo[4,3-e]pyridine, chromeno[2,3-b][1,3]thiazolo[5,4-e]pyridine and chromeno[2,3-b]quinoline were efficiently synthesized from reaction of carbonitrile 1 with some cyclic methylene compounds. Heteroannulated chromeno[3′,2′:5,6]pyrido[2,3-d]pyrimidines and chromeno[2,3-b][1,8]naphthyridines were synthesized from reaction of compound 2 with formic acid, formamide, and malononitrile, cyanoacetamide, respectively. Chromeno[2′,3′:6,5]pyrido[2,3-b][1,8]naphthyridine 17 was synthesized from reaction of compound 2 with malononitrile dimer. Structures of the newly synthesized products were deduced based on their analytical and spectral data. [ABSTRACT FROM AUTHOR]