Digging into the mechanism of oxidative Pd(II)-catalyzed aminations

Although the Pd(II)-catalyzed alkene aminopalladation and allylic C-H activation have been much described in literature, the in-depth mechanism of such type of process is far from being a simple matter. This account focuses on the oxidative intramolecular Pd(II)-catalyzed amination of unsaturated N-sulfonyl carbamates and carboxamides, revealing that different mechanistic paths can be operative. In particular, after activation of the unsaturation by Pd(II) catalyst, aminopalladation can take place, affording the corresponding high-energy cyclic (5- or 6-membered) aminopalladated intermediate (AmPI). This latter can evolve along different pathways, such as: distocyclic beta-H elimination, oxidation by a strong terminal oxidant, or carbopalladation. Otherwise, the cyclic AmPI can lay dormant, in equilibrium with the initial substrate. In this case, alternative reactivities may take place, such as allylic C-H activation of the olefinic substrate, [3,3]-sigmatropic rearrangement, or decomposition.