Triazolopyridines. 18. Nucleophilic substitution reactions on triazolopyridines; a new route to 2,2′-bipyridines

X-Ray characterization of 3-methyl-6,8-di(2-pyridyl)-[1,2,3]triazolo[5',1':6,1]pyrido[2,3-d]pyrimidine

“…Reaction of the lithio derivative 4 with a mole of 2-cyanopyridine gives the intermediate 5, which reacts with a second mole of reagent forming a new intermediate 6, as we have proposed. 2 Attack to the activated 7-position towards nucleophilic substitution, 4 leads to the intermediate 7 that would in turn produce 8. After protonation, a new intermediate 9 is formed, that undergoes an electrocyclic process (6π) followed by oxidation to give 3.…”

Triazolopyridines 21.1 The stereochemistry of 1-[1,2,3]triazolo[1,5-a] pyridin-7-yl-4-(2H-[1,2,3]triazol-4-yl)-1,3-butadienes and triazolo ring opening derivatives

“…It was known, 5 that similar azolyldiene derivatives were formed when [1,2,3]-triazolopyridinium salts reacted with nucleophiles. In all the reported cases the double bond of the diene attached to the triazole retained its original cis geometry.…”

“…Previously, we have reported that 1- [1,2,3]triazolo [1,5-a]pyridin-7-yl-4-(2H- [1,2,3]triazol-4-yl)-1,3-butadienes 1 can be synthesized together with bitriazolopyridines 2 in the lithiation reaction of [1,2,3]triazolo [1,5-a]pyridines 3, when reactions are carried out at -70 ºC in THF as solvent, and the mixture allowed to rise room temperature before hydrolysis, 2,3 (Scheme 1). We had nmr evidence that the intermediate 4 was formed, and this may undergo six-membered ring opening to give 1 or loss of hydride to give 2.…”

“…[4][5][6] In those cases azolyldiene derivatives with different geometry were found depending on nucleophile size and electronegativity. We now wish to report a study of the geometry of azolyldienes 1a,b and of new 1-(6-substituted-2-pyridyl)-4-(2H- [1,2,3]triazol-4-yl)-1,3-butadienes 8-10, obtained from compounds 1 and sulfuric acid, acetic acid, or selenium dioxide. …”

Triazolopyridines 22.1 Description of new 7,9-di(2-pyridyl)[1,2,3]triazolo[5',1':6,1]pyrido[3,2-d]pyrimidines

“…2,3 We have recently discovered a facile route to new potential helicating ligands 2a-d, 3a-d, 5d, and 6 from triazolopyridines 1a-d (scheme 1). 4,5 Following this study we have designed new ligands 7-10, which can be easily accessible from compound 5d if the methodology summarized above is applicable (see scheme 2). The understanding that the availability of 5d is important to success, led us to try its synthesis in an attempt to improve the reported yield.…”