Direct Formation of 2-Substituted 2H-Indazoles by a Pd-Catalyzed Reaction between 2-Halobenzyl Halides and Arylhydrazines

Nayyef Aljaar, Mousa Al-Noaimi, Jürgen Conrad and Uwe Beifuss*

*Bioorganische Chemie, Institut für Chemie, Universität Hohenheim, Garbenstraße 30, Stuttgart D-70599, Germany, Email: ubeifussuni-hohenheim.de

N. Alijaar, M. Al-Noaimi, H. Conrad, U. Beifuss, J. Org. Chem., 2021, 86, 1408-1418.

DOI: 10.1021/acs.joc.0c01923

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Abstract

Pd catalyzes a direct and operationally simple regioselective synthesis of 2-aryl-substituted 2H-indazoles in good yields from easily available 2-bromobenzyl bromides and arylhydrazines via a regioselective intermolecular N-benzylation followed by intramolecular N-arylation and oxidation. The reaction employs Cs₂CO₃ as the base and t-Bu₃PHBF₄ as the ligand in DMSO at 120°C.

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proposed mechanism

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Key Words

2H-Indazoles

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ID: J42-Y2021