The Reaction Mechanism of the Hydroamination of Alkenes Catalyzed by Gold(I)−Phosphine:  The Role of the Counterion and the N-Nucleophile Substituents in the Proton-Transfer Step

Abstract

The reaction mechanism of the gold(I)-phosphine-catalyzed hydroamination of 1,3-dienes was analyzed by means of density functional methods combined with polarizable continuum models. Several mechanistic pathways for the reaction were considered and evaluated. It was found that the most favorable series of reaction steps include the ligand substitution reaction in the catalytically active Ph3PAuOTf species between the triflate and the substrate, subsequent nucleophile attack of the N-nucleophile (benzyl carbamate) on the activated double bond, which is followed by proton transfer from the NH2 group to the unsaturated carbon atom. The latter step, the most striking one, was analyzed in detail, and a novel pathway involving tautomerization of benzyl carbamate nucleophile assisted by triflate anion acting as a proton shuttle was characterized by the lowest barrier, which is consistent with experimental findings.

Inner-Sphere versus Outer-Sphere Coordination of BF4– in a NHC-Gold(I) Complex

“…Active gold(I) catalysts are often postulated to be monocoordinated outer-sphere ion-pairs with an unspecified second ligand L', [Au(L)(L')][X] (VI). 15 These structures with an "empty coordination site" on gold are frequently proposed based on the known low dissociation energies of the counterions used, 12,16 without spectroscopic or structural data to support these claims. 17 For these putative species, the second coordination site on the gold (I) center 33 nickel, 34 copper, 35 zinc, 36 rhodium, 37 silver, 38 and platinum.…”

The Role of Solvent on the Mechanism of Proton Transfer to Hydride Complexes: The Case of the [W3PdS4H3(dmpe)3(CO)]+ Cubane Cluster

“…(1) ], which can be stable or release H 2 in a subsequent step. The reaction steps and the position of the equilibrium of the proton-transfer reaction represented in Equation (1) depends on the relative acidity and basicity of interacting molecules and on the interaction with counterions, [7,8] or the solvent. [9] Theoretical and experimental investigations support the surrounding medium influence on the potential energy surface (PES) of the reaction mechanism.…”

Gold-catalyzed bis-cyclization of 1,2-diol- or acetonide-tethered alkynes. Synthesis of ?-lactam-bridged acetals: a combined experimental and theoretical study

“…In particular, a recent theoretical study on the hydroamination of alkenes catalyzed by gold(I)-phosphine has proved the adequacy of replacing the PPh 3 ligand by the PH 3 one. 24 Besides, the Brønsted acid theoretically employed, BSA, reasonably represents the main features of the experimental one PTSA on the basis of similar pKa values.…”