Triazolopyridines. Part 2. Preparation of 7-substituted triazolo[1,5a]pyridines by directed lithiation

Abstract

The lithiation reactions of 1,2,3-triazolo[1,5-a]pyridine (1) to give the 7-lithio-derivative (4; R = Li), and of its 7-methyl derivative (16) to give the 7-lithiomethyl compound, are described. These lithium derivatives react with electrophiles, notably aldehydes and ketones, to give triazolopyridin-7-yl derivatives (5a–h), (8), (10), (17), and (20). Selected 7-substituted triazolopyridines react with bromine to give 2-dibromomethylpyridines, and hence 6-substituted pyridine-2-carbaldehydes.