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

Abstract

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.

Novel synthesis of 2‐aminoquinoline‐3‐carbaldehyde, benzo[b][1,8]naphthyridines and study of their fluorescence behavior

“…In the earlier communication 23, 24, we have studied Friedländer condensation on 5‐aminopyrazole‐4‐carbaldehyde (orthoaminoaldehyde) with various active methylenes. Herein, we studied the annelation of pyridine ring onto quinoline nucleus by condensing 7 with benzoylacetonitriles.…”

Synthesis of various pyrazole-fused heterocyclic systems using pyrazole-4-carbaldehydes as versatile precursors

“…Condensation of 5-amino-1H-pyrazole-4-carbaldehyde 11 with propiophenone 2j afforded 3-(4-aryl)-5methyl-6-phenyl-1H-pyrazolo [3,4-b]pyridine derivatives 12 57 . On the other hand, condensation of 5aminopyrazole-4-carbaldehydes 11 and unsymmetric dialkylketones 2f yielded a mixture of isomeric pyrazolo [3,4-b]pyridine derivatives 13 and 14 58 .…”

“…Friedländer condensation of 5-amino-1H-pyrazole-4-carbaldehyde 11 with acetonitrile derivatives 2 in ethanol in the presence of a catalytic amount of piperidine yielded the corresponding pyrazolo [3,4-b]pyridine-5-carbonitriles 16 58,59 . 6-Aminopyrazolo [3,4-b]pyridines 18 were obtained by the condensation of 1 with the corresponding cyanomethyl derivatives 17 57,[59][60][61] (Scheme 6). Panda et al 62 reported that treatment of 5-amino-1H-pyrazole-4-carbaldehyde 11a and 11b with various active methylene compounds 17a-c in the presence of an excess of sodium methoxide heated at reflux in methanol gave the corresponding pyrazolo [3,4-b]pyridines 7a-f (Scheme 7).…”

New Synthesis and Reactions of Ethyl 5‐amino‐4‐cyano‐1‐phenyl‐1H‐pyrazole‐3‐carboxylate

“…However, both established methods were suffered from disadvantages of low yield, tedious workup, and requirement of low temperature below −5°C for the latter method. In continuation of our recent work aiming at the synthesis of various new pyrazole derivatives , we report a new method for the synthesis of ethyl 5‐amino‐4‐cyano‐1‐phenyl‐1 H ‐pyrazole‐3‐carboxylate 5 and novel pyrazolopyrimidine, N ‐alkylated pyrazolo[3,4‐ d ]pyridazin‐7‐one, and 3‐(hydrazinylcarbonyl)pyrazole‐4‐carboxamide derivatives, which have been tested for their antimicrobial activity.…”