Triazolopyridines. Part 6. Ring opening reactions of triazolopyridines

Abstract

The triazole ring in 1,2,3-triazolo[1,5-a]-pyridines and -quinolines, and in 1,2,3-triazolo[5,1-a]isoquinolines can be opened with loss of nitrogen. The reagents described are bromine, aqueous sulphuric acid, glacial acetic acid, and selenium dioxide; the products from the triazolopyridines are dibromomethyl, hydroxymethyl, acetoxymethyl, and acyl derivatives of pyridine. The generality of the reactions is discussed. The first reported reaction in which the six-membered ring of a 1,2,3-triazolo[1,5-a] pyridine is opened, by hydride reduction, gives a triazolylbutadiene.