An efficient synthesis of 1-H indazoles

Design, synthesis and evaluation of N-benzoylindazole derivatives and analogues as inhibitors of human neutrophil elastase

“…Compound 17a was obtained from compound 16 37 by reaction with m -toluoyl chloride, following the procedure described for 3a–k, 3m , and 3q . After evaporation of the solvent, cold water was added to the residue, followed by neutralization with 0.5 N NaOH.…”

“…Scheme 4 depicts the synthetic routes followed to obtain 17a , b and 19a , b , where the function at position 3 was replaced with a methyl group ( 17a , b ), a carboxylic group ( 19b ), or a hydrogen ( 19a ). Treatment of the commercially available o -bromoacetophenone 15 with hydrazine hydrate at high temperature afforded the 3-methylindazole 16 , 37 which was transformed into the final compounds 17a , b , as reported in Scheme 1. Following the same procedure, final product 19a 38 was synthesized.…”

Synthesis of indazole motifs and their medicinal importance: An overview

“…However, under the same reaction conditions benzaldehyde react with hydrazine hydrate to form hydrazones (Scheme-01) [14]. Ortho-bromo benzaldehyde react with arylhydrazines in toluene at 100 0 C in the presence of catalytic amount of a palladium and phosphorus chelating ligands 1, 1-bis (diphenylphosphino) ferrocene and 1, 3-bis (diphenylphosphino)-propane along with NaO t -Bu affords 1-aryl-1H-indazoles was reported (Scheme-02) [15].…”

Transition‐Metal‐Catalyzed Syntheses of Indazoles

“…Early approaches towards the synthesis of indazoles were largely based on metal-free classical synthetic routes such as diazotization, nitrosation, base-catalyzed condensation reactions, and dipolar cycloaddition reactions. [10][11][12] Ever since the development of homogeneous transition metal catalysis, synthetic organic chemistry witnessed enormous progress and many unconventional protocols were made possible in a commanding way. [13] Indazole synthesis also took advantage of this versatile protocol and most of the newly developed approaches follow transition metal catalysis.…”