Regioselective Synthesis of 1‐Substituted Indazole‐3‐carboxylic Acids

Abstract

In this article, we study the synthesis of 1‐substituted indazole‐3‐carboxylic acids from 2‐halobenzoic acids.

Regioselective N-alkylation of the 1H-indazole scaffold; ring substituent and N-alkylating reagent effects on regioisomeric distribution

“…While only a few naturally occurring indazoles have been reported in the literature [2][3][4], such as the alkaloids nigellicine (1) and nigelli-dine (2), there are a myriad of synthetic indazole derivatives known that display a broad range of biological activities. For example, several N-1 and N-2-substituted indazoles are currently marketed or under clinical investigation for the treatment Scheme 1: Synthetic approaches to N-1 substituted indazole derivatives [12][13][14].…”

Expedient synthesis of E -hydrazone esters and 1 H -indazole scaffolds through heterogeneous single-atom platinum catalysis

“…1) that exhibit a broad range of anti-inflammatory, antidepressant, anticancer, and/or antifertility properties ( 13 ); examples include lonidamine ( 14 ), adjudin ( 14 ), gamendazole ( 15 ), and the U.S. Food and Drug Administration (FDA)–approved granisetron ( 16 ). A direct and convenient approach to assemble the 1 H -indazole nucleus involves the synthesis of aryl-substituted E -α-hydrazone esters, followed by intramolecular cyclization with the neighboring aryl motif ( 17 ). Current methods that afford α-hydrazone esters typically involve the condensation of hydrazine with α-ketoesters under harsh acidic conditions ( 18 ) and sometimes require the use of sensitive reagents at cryogenic temperatures ( 19 ).…”

Copper‐Assisted Synthesis of Novel Pyrazolo[3,4‐d]thiazoles

“…[25] Therefore, we turned to the Ullmann cross coupling reaction. While the presence of a ligand did not improve the reaction yield ( Table 1, entry 8 vs entry 9), [26] a polar aprotic solvent screening ( Table 1, entries 9-11) managed to identify the best conditions for the cyclisation step (Table 1, entry 11), used as Conditions C from now on. While the presence of a ligand did not improve the reaction yield ( Table 1, entry 8 vs entry 9), [26] a polar aprotic solvent screening ( Table 1, entries 9-11) managed to identify the best conditions for the cyclisation step (Table 1, entry 11), used as Conditions C from now on.…”