Novel Alternative for the N-N Bond Formation through a PIFA-Mediated Oxidative Cyclization and Its Application to the Synthesis of Indazol-3-ones

摘要

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