Synthesis of pyrazolo‐annelated heterocyclic ring compounds such as pyrazolo[3,4‐<i>b</i>]pyridines and pyrazolo[4′,3′:5,6]‐pyrido[2,3‐<i>d</i>]pyrimidines

Abstract

Abstract magnified image A series of pyrazolo[3,4‐ b ]pyridines has been synthesized by Friedländer condensation of 5‐amino‐pyrazole‐4‐carbaldehyde 1 with active methylene compounds in basic medium. Pyrazolo[4′3′:5,6]pyrido‐[2,3‐ d ]pyrimidines have been synthesized from pyrazolo[3,4‐ b ]pyridines using substituted urea and acetic anhydride.