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Regioselective Synthesis of 2H-Indazoles Using a Mild, One-Pot Condensation-Cadogan Reductive Cyclization

Nathan E. Genung*, Liuqing Wei and Gary E. Aspnes

*CVMED Medicinal Chemistry, Pfizer Inc., Eastern Point Road, Groton, Connecticut 06340, United States, Email:

N. E. Genung, L. Wei, G. E. Aspnes, Org. Lett., 2014, 16, 3114-3117.

DOI: 10.1021/ol5012423


In an operationally simple, mild and efficient one-pot synthesis of 2H-indazoles from commercially available reagents, ortho-imino-nitrobenzene substrates, generated via condensation, undergo reductive cyclization promoted by tri-n-butylphosophine to afford substituted 2H-indazoles. Various electronically diverse ortho-nitrobenzaldehydes and aromatic as well as aliphatic amines were examined.

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Key Words

2H-indazoles, tributylphosphine

ID: J54-Y2014