Oxidative N-N Bond Formation Versus the Curtius Rearrangement

The oxidative formation of N-N bonds from primary amides has been recently reported and then retracted in the journal Nature Communications by Kathiravan, Nicholls, and co-authors, utilizing a hypervalent iodane reagent. Unfortunately, the authors failed to recognize the Curtius reaction taking place under the described reaction conditions. Thus, the claimed N-N coupling products were not formed. Instead, the Curtius rearrangement urea coupling products were obtained. We demonstrate this herein by means of NMR and x-ray analysis, as well as with the support of an alternative synthetic route. We present herein some experimental results, including NMR and x-ray, which have led to the recent retraction of a Nature Communications article claiming to feature a metal-free cross-dehydrogenative N-N coupling of primary amides with amines under the action of a hypervalent iodine oxidant. These findings should help the chemical research community to avoid such pitfalls in the future. image