Regioselective Synthesis of 2H-Indazoles Using a Mild, One-Pot Condensation–Cadogan Reductive Cyclization
2014
Genung, Nathan E. | Wei, Liuqing | Aspnes, Gary E.
An operationally simple and efficient one-pot synthesis of 2H-indazoles from commercially available reagents is reported. Ortho-imino-nitrobenzene substrates, generated via condensation, undergo reductive cyclization promoted by tri-n-butylphosophine to afford substituted 2H-indazoles under mild reaction conditions. A variety of electronically diverse ortho-nitrobenzaldehydes and anilines were examined. To further extend the scope of the transformation, aliphatic amines were also employed to form N2-alkyl indazoles selectively under the optimized reaction conditions.
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