Synthesis of Indazoles by the [3+2] Cycloaddition of Diazo Compounds with Arynes and Subsequent Acyl Migration

The [3+2] cycloaddition of a variety of diazo compounds with o-(trimethylsilyl)aryl triflates in the presence
of CsF or TBAF at room temperature provides a very direct, efficient approach to a wide range of
potentially biologically and pharmaceutically interesting substituted indazoles in good to excellent yields
under mild reaction conditions. Simple diazomethane derivatives afford N-unsubstituted indazoles or
1-arylated indazoles, depending upon the stoichiometry of the reagents and the reaction conditions, while
dicarbonyl-containing diazo compounds undergo carbonyl migration to afford 1-acyl or 1-alkoxycarbonyl
indazoles selectively.