Dual Gold Catalysis: Stepwise Catalyst Transfer via Dinuclear Clusters

Abstract

The interest in and use of dual gold catalysts is forever increasing, but little is known of the mechanism for the catalyst transfer and its effect on the continued high turnover frequency. Herein, we present a computational investigation of the mechanism for the final intermolecular catalyst transfer in the synthesis of dibenzopentalene from 1-ethynyl-2-(phenylethynyl)benzene. Three different scenarios have been explored: a single catalyst transfer from the monoaurated product complex, the analogous water mediated single transfer, and a dual catalyst transfer from the diaurated product complex. Transition structures have been found for each step of the three possible pathways, and a stepwise dual catalyst transfer has proven to be the lowest energy pathway. We here describe a three-step transfer of two gold moieties from one dibenzopentalene to one diyne. This process directly gives the σ,π-gold coordinated diyne for the further intramolecular cyclization reaction.

An unexpected transmetalation intermediate: isolation and structural characterization of a solely CH3 bridged di-copper(i) complex

“…20 Despite that aurophilic interactions are much stronger than cuprophilic interactions (15 vs. 4 kcal/mol), 21 our findings suggest that the latter can also foster ligand redistribution and organic group transfer.…”

Double Gold Activation of 1‐Ethynyl‐2‐(Phenylethynyl)Benzene Toward 5‐exo‐dig and 6‐endo‐dig Cyclization Reactions

“…While an exponential growth of activity in the field of homogeneous gold catalysis of organic reactions has been observed in the last 16 years, it is only recently that the concept of dual activation has been discovered . In this reaction mode, which has no precedence in organometallic chemistry, the organic substrate in the reactive species is activated by two mononuclear gold complexes at the same time, one coordinating in a σ‐mode to a terminal alkyne, the other in a π‐mode coordinated to a second alkynyl unit (see 1 in Figure for a representative example) . Two different reaction modes are then possible, either a 5‐ exo ‐dig cyclization leading to a five‐membered carbocycle with an exocyclic gold(I) vinylidene unit or a 6‐ endo ‐dig cyclization leading to a six‐membered carbocycle bonded to gold and bearing a positive charge in vicinal position to the gold complex.…”

Different Selectivities in the Insertions into C(sp2)−H Bonds: Benzofulvenes by Dual Gold Catalysis Competition Experiments

“…The σ,π‐activated starting material then undergoes a 5‐ endo‐dig cyclization forming vinylidene III , which then is attacked by the in‐plain phenyl group. After formation of the gem ‐diaurated species V a transfer of the two gold atoms onto the next starting material under liberation of the product closes the catalytic cycle ,…”