A Mechanistic Study of the Cu‐catalyzed N‐arylation of Hydantoin with Aryl(TMP)iodonium Salts

Abstract The use of diaryliodonium salts in organic reactions has rapidly increased in the last decade because of their efficiency in arylation reactions. Despite this, mechanistic investigations are still scarce, particularly for copper catalyzed N‐arylation reactions. Recently, we published the use of the unsymmetrical aryl(TMP)iodonium salts (TMP=2,4,6‐trimethoxyphenyl) for the selective Cu‐catalyzed N‐arylation of hydantoins. In this work, the mechanism of this reaction has been studied by DFT methods, and our results have been compared with previous and new experimental data. In contrast to the mechanism proposed for C−H arylation reactions, our results suggest that deprotonation of hydantoin precedes the oxidative addition of aryl(TMP)iodonium salt, with the oxidative addition to a Cu(I) imido intermediate and ligand rearrangements being the rate‐limiting steps. This mechanism agrees with the species observed by NMR spectroscopy, kinetic isotope experiments, and the product yields observed using aryl(TMP)iodonium salts with different steric and electronic properties. In addition, it gives some hints for increasing the efficiency of arylation reactions by tuning the diaryliodonium salt.