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Preparation of pyrazolo 1 5 a pyridine and 1 2 4 triazolo 1 5 a pyridine derivatives from 1 6 diaminopyridine 2 thiones


, : Preparation of pyrazolo 1 5 a pyridine and 1 2 4 triazolo 1 5 a pyridine derivatives from 1 6 diaminopyridine 2 thiones. Heterocycles (Tokyo) 27(3): 733-744

The 1,6-diaminopyridine-2-thiones (1a and 1b) react with .alpha.-halocarbonyl compounds to given the phyrido [2,1-b] [1,3,4]thiadiazinium-salts (2) which undergo base-catalyzed ring-contraction to give the pyrazolo[1,5-a]pyridines (3) or (4). The reactions of the N-amino-heterocycles (1a and 1b) with nitriles lead direcetly to [1,2,4]triazolo-[1,5-a]pyridines (5).

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