Iridium(III)-Catalyzed Direct Intermolecular Chemoselective α-Amidation of Masked Aliphatic Carboxylic Acids with Dioxazolones via Nitrene Transfer

The Ir(III)-catalyzed direct α-C–H amidation of imidazole-masked aliphatic carboxylic acids with dioxazolones is reported. The presence of an imidazole moiety as a directing group is a key to the success of the reaction. The products can be easily converted to esters and amides in a simple procedure. The reaction shows a broad substrate scope for various substituted 2-acylimidazoles, as well as a variety of dioxazolone derivatives with important functional groups being tolerated. The reaction mechanism was investigated by deuterium-labeling experiments, Hammett plots, NMR, and FAB-MS, and we propose the generation of an iridium nitrene intermediate.