Origin of the Anti-Markovnikov Hydroamination of Alkenes Catalyzed by L–Au(I) Complexes: Coordination Mode Determines Regioselectivity

Abstract

The reaction mechanism and regioselectivity for the gold­(I)-catalyzed hydroamination reaction of terminal alkenes are analyzed by means of density functional theory (DFT) calculations. The influence of the nature of the olefin as well as the ligand present in the gold­(I) catalyst on the regioselectivity is investigated. The anti-Markovnikov addition is preferred for some alkenes, particularly those having cyclopropyl or good electron-withdrawing groups in their structures. The regioselectivity of the process is quantitatively analyzed with the help of state-of-the-art computational methods, namely, the activation strain model (ASM) of reactivity and natural orbitals for chemical valence (NOCV) method. It is found that the back-bonding interactions in the initially formed π-complex are directly related to the Gibbs energy barrier difference between the Markonikov and anti-Markovnikov additions. It can be concluded that the coordination mode of the initial π-complex ultimately controls the regioselectivity outcome of the transformation.

Catalytic Au(i)/Au(iii) arylation with the hemilabile MeDalphos ligand: unusual selectivity for electron-rich iodoarenes and efficient application to indoles

“…S30†). 14,21 For both gold and palladium, the electrostatic term contributes to 49–52% of the interaction between the metal fragment and substrate, while the orbital term accounts for 40–42%. The primary orbital interaction is associated with substrate to metal donation for gold, but metal to substrate back-donation for palladium.…”

PyFrag 2019—Automating the exploration and analysis of reaction mechanisms

“…For instance, we have previously used the ASM to understand how the reaction barrier varies when different bonds are activated by palladium, or how ligands can change the activating capability of palladium, or how and why other metal centers perform differently in cross‐coupling reactions compared to palladium . In addition, the ASM has been successfully applied to understand the quantitative factors governing molecular reactivity in other systems like cycloadditions, metalorganic catalysis, and substitution reactions …”

Tuning Activity and Selectivity during Alkyne Activation by Gold(I)/Platinum(0) Frustrated Lewis Pairs

“…Thus, if 2 approaches the acetylene adduct along the Au–C 2 H 2 direction, the corresponding vinylene 4b forms (Δ G ⧧ = 23.4 kcal mol –1 from the 1b : 2 Lewis pair + acetylene), in a process somehow reminiscent of the gold-mediated nucleophilic attack over activated alkynes (e.g., gold-catalyzed hydroamination). 23 In contrast, the alignment of the basic 2 in an orthogonal disposition with respect to the Au–C 2 H 2 bond results in deprotonation of the activated acetylene (15.6 kcal mol –1 for the pair 1b : 2 ) to yield the corresponding Au(I) terminal acetylide [(PMe 2 Ar Dipp2 )Au(C≡CH)] ( 5b ) and [Pt(P t Bu 3 ) 2 H][NTf 2 ] ( 6 ). These two fragments readily rearrange to intermediates [(PR 2 Ar′)Au(μ-η 1 :η 2 -C≡CH)Pt(H)(P t Bu 3 ) 2 ] + ( A ) that subsequently evolve to compounds 3 by rapid σ,π isomerization of the bridging μ-C≡CR unit.…”