Novel Alternative for the N<i>−</i>N Bond Formation through a PIFA-Mediated Oxidative Cyclization and Its Application to the Synthesis of Indazol-3-ones<sup>†</sup>

The synthesis of a series of N,N<i>‘</i>-disubstituted indazolone derivatives starting from methyl anthranilates is presented. This general approach features a novel and easy way for access to the target <i>N</i>-heterocycles by formation of a new N<i>−</i>N single bond. The key cyclization step embraces the formation of an <i>N</i>-acylnitrenium intermediate, mediated by the hypervalent iodine reagent PIFA, and its succeeding intramolecular trapping by the amine moiety under rather mild experimental conditions.