Synthetic strategies and anticancer evaluation for the novel 3-(6-heteroaryltriazolo[3,4-b][1,3,4]thiadiazol-3-yl)chromeno [2,3-b]pyridines

The novel chromonyltriazolo[3,4-b][1,3,4]thiadiazole derivative 5 was efficiently synthesized and utilized as key intermediate for construction of a diversity of heterocyclic rings; through reactions with binucleophilic reagents. Treating electron deficient substrate 5 with hydrazine hydrate, phenylhydrazine and hydroxylamine furnished pyrazolyl/isoxazolyltriazolo[3,4-b][1,3,4]thiadiazoles 6-8. Also, reacting substrate 5 with guanidine, cyanoguanidine and thiourea provided pyrimidinyltriazolo[3,4-b][1,3,4]thiadiazoles 9-11. Reaction of substrate 5 with ethylenediamine and o-phenylenediamine afforded diazepine derivatives 12 and 13. Reaction of substrate 5 with malononitrile, ethyl cyanoacetate and cyanoacetamide afforded pyrans 14, 15 and pyridine 16 linked triazolo[3,4-b][1,3,4]thiadiazolyl chromeno[2,3-b]pyridines. The anticancer efficiency of the current compounds presented diverse inhibitory action against certain cancer cell lines. On the basis of analytical and spectral findings, the structures of the synthesized products were confirmed.