Metal-Free N-N Bond-Forming Route to Indazoles

Significance

An article from 1962 (A. Hassner, M. J. Michelson J. Org. Chem. 1962, 27, 298) inspired the present authors to utilize electrophilic amination as the cyclizative step in the synthesis of indazoles. Using a combination of MsCl and triethylamine, various o-aminophenyl oximes were converted into the corresponding indazoles in modest to good yields. By careful control of concentration and stoichiometry, possible side reactions, such as Beckmann and Neber rearrangements, were subjugated. Primary amines afford higher yields than secondary amines in the reaction. The substrate scope was rather inadequately studied.