title: The chemistry of [1,2,3]triazolo[1,5-a]pyridines.
abstract: The reactivity of [1,2,3]triazolo[1,5-a]pyridines 1 is described. Triazolopyridines react with electrophiles in two contrasting ways, giving 3-substituted triazolopyridines 2, or products 3, resulting from triazolo ring opening with loss of molecular nitrogen. The triazolopyridines can be lithiated at -40 degrees C by lithium diisopropylamide in ether giving regiospecifically the 7-lithio derivative. Bromotriazolopyridines have activation towards nucleophilic substitution at position 5 and 7, and benzenoid inertness at position 6. The parent compound 1a is easily hydrogenated giving tetrahydrotriazolopyridine 11a in high yield; when the triazolopyridines have substituents, the hydrogenation reaction strongly depends on the position of the substituent. Triazolopyridinium ylides of type 18 and 26 react with acetylenic esters; these reactions are influenced by the nature of solvent and the acetylenic ester used, giving different types of adducts: stable disubstituted triazolopyridinium ylides of type 19 and 20, indolizines 21, or pyrroleninylpyrazolo[5,1-a] pyridines 22. Photochemistry, and photochemical reactions with MP and DMAD of these ylides are also described. A new way to 2,2'-bipyridines, in two steps from triazolopyridines is reported.
authors.affiliation: Departamento de Química Orgánica, Facultad de Farmacia, Universidad de Valencia, Avda. Vicente Andrés Estellés s/n, 46100 Burjassot, Valencia, Spain. belen.abarca@uv.es
authors.forename: Belén
authors.initials: B
authors.lastname: Abarca-González
mesh_terms: D003500:Cyclization; D006865:Hydrogenation; D010777:Photochemistry; D011725:Pyridines / Q000737:chemistry*; D011726:Pyridinium Compounds / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D014230:Triazoles / Q000737:chemistry*
chemical_list: D011725:Pyridines; D011726:Pyridinium Compounds; D012997:Solvents; D014230:Triazoles