Kinetic, Spectroscopic, and Computational Investigation of Oxidative Aminative Alkene Cleavage Reveals an N-Iodonium-Iminoiodinane Pathway

The combination of hypervalent iodine(III) oxidants and ammonia sources has been applied in various oxidative aminative transformations of high synthetic value. Central to these reactions is the proposed in situ generation of a four-electron oxidizing intermediate, commonly referred to as iodonitrene. However, this species’ mechanism of formation, nature, and relevance to N-atom transfer remains uncertain. Furthermore, evidence for its direct implica-tion as the key reactive intermediate remains elusive. Herein, we present an extensive mechanistic study of a re-cently published oxidative aminative cleavage of alkenes, which allowed us to obtain key insights into these under-studied aspects of hypervalent iodine-mediated nitrogen atom insertion. Through in situ 19F nuclear magnetic reso-nance (NMR), initial rate kinetics, linear free energy relationships (LFER), H/D and 12C/13C kinetic isotope effect (KIE) determination, electrospray ionization mass spectrometry (ESI-MS) and density functional theory (DFT) stud-ies, we show that the formation of an N-iodonium-iminoiodinane is rate-determining in this reaction. This species is highly electrophilic and capable of concerted, asynchronous transfer of a [PhI–N]+ unit to double bonds. These find-ings point towards the N-iodonium-iminoiodinane, not an iodonitrene, being the active N-atom transfer agent gen-erated from the combination of hypervalent iodine(III) oxidants and ammonia. This ultimately deepens our under-standing of this commonly used reagent combination and will help to inform the development of methods and rea-gents for oxidative amination reactions using this reactive manifold.