Synthesis of 1,5-disubstituted-4-oxo-4,5-dihydro-1 H -pyrazolo[4,3- c ]pyridine-7-carboxamides

1,5-Disubstituted-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c]pyridine-7-carboxamides functionalized at positions 1, 5, and 7 were prepared in six straightforward steps from cheap, commercially available dialkyl acetone-1,3-dicarboxylate. Due to the instability of methyl 1-benzyl-substituted pyrazolo[4,3-c]pyridine-7-carboxylates under basic hydrolytic conditions (LiOH/H2O), a detour via the corresponding benzyl esters was introduced to deliver the final 1-benzyl-substituted-bicyclic carboxamides in seven steps. The designed synthetic route is suitable for the construction of a larger library of compounds. All the key compounds have been characterized by NMR spectroscopic techniques and X-ray analysis.