907. Heterocyclic systems related to pyrrocoline. Part II. The preparation of polyazaindenes by dehydrogenative cyclisations

Synthesis, X-ray crystal structures, spectroscopy and electrochemistry of ruthenium(II) complexes of two chelating ligands containing [1,2,3]triazolo[1,5-a]pyridine subunits

“…Curiously however, this ring system has been ignored as a ligand in coordination chemistry. There have been only a few reports of complexes with a [1,2,3]triazolo[1,5-a]pyridine unit acting as a donor to a metal centre [23][24][25][26][27][28][29][30]. Several of these [24][25][26] involve complexes of the chelating ligand (2), which represents a bpy analogue with one of the two pyridine rings replaced by a [1,2,3]triazolo[1,5-a]pyridine unit.…”

Product Class 5: Azaindolizines with Two Nitrogen Atoms in the Five-Membered Ring

“…[181] The yield was 23% in the early paper, but has been improved later up to 71%. This method was the first used for the synthesis of pyrazolo[1,5-a]pyridine (Scheme 48).…”

Dehydrogenation of Hydrazones

“…A secondary reaction in the case of 2-diazomethylpyridine, formed by dehydrogenation of pyridine-2-aldehydrazone, is the rapid [1,5] cyclization to 1,2,3-triazolo [3,4-a] pyridine 3 (R = H) (17,18). Diazoketones of the same type-for example, with R = benzoyl (5) or 2-pyridoyl (19,20)-react in the same way.…”