Study of the heterocyclization of vic ‐substituted hydrazides of acetylenylpyrazolecarboxylic acids into N ‐amino pyrazolopyridinones

Abstract We report a new and efficient methodology to prepare N ‐amino pyrazolo[4,3‐ c ]pyridin‐4‐ones 4 and N ‐amino pyrazolo[3,4‐ c ]pyridin‐4‐ones 8 from vic ‐acetylenyl/hydrazido pyrazoles. The procedure involves the intermediate synthesis of methyl esters of acetylenyl‐pyrazole carboxylic acids and the subsequent cyclization under a variety of conditions.