Synthesis of 2<i>H</i>-Indazoles by the [3 + 2] Dipolar Cycloaddition of Sydnones with Arynes

Abstract

A rapid and efficient synthesis of 2H-indazoles has been developed using a [3 + 2] dipolar cycloaddition of sydnones and arynes. A series of 2H-indazoles have been prepared in good to excellent yields using this protocol, and subsequent Pd-catalyzed coupling reactions can be applied to the halogenated products to generate a structurally diverse library of indazoles.