Abstract A one??pot and convenient synthesis of multisubstituted pyrazolo [3, 4??b] pyridines in moderate to high yields has been achieved by a two??step reaction: diazo??transfer of 5?? azido??1??phenylpyrazole??4??carboxaldehydes to ketones in ethanolic KOH to give 5??amino?? 1??phenylpyrazole??4??carboxaldehyde and subsequent Friedlaender reaction of 5??amino??1?? phenylpyrazole??4??carboxaldehyde with ketones.