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: nathan.genungbiogen.com
N. E. Genung, L. Wei, G. E. Aspnes, Org. Lett., 2014, 16, 3114-3117.
DOI: 10.1021/ol5012423 (free Supporting Information)
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.
see article for more examples