The Role of Acetylides in Dual Gold Catalysis: A Mechanistic Investigation of the Selectivity Difference in the Naphthalene Synthesis from Diynes

Abstract

Under the conditions of dual activation catalysis with oxygen nucleophiles, β‐substituted naphthalenes were obtained from 1,2‐diethinyl arenes. Mechanistic studies, which include isotope labeling experiments, support that dual activation leads to β‐substituted naphthalenes, whereas α‐naphthalenes are formed by π activation only, and no gold acetylide or dual activation is involved in the formation of the α‐substituted products. Additional experiments on substrates that led to dibenzopentalenes support these mechanistic insights.

Dispersion, solvent and metal effects in the binding of gold cations to alkynyl ligands: implications for Au(i) catalysis

“…Slow diffusion of Et 2 O into these solutions afforded green crystals suitable for study by X-ray diffraction. A peak in the ESI-MS of [6]SbF 6 at m/z 1475.4042, with the correct isotopic distribution pattern, confirmed the presence of the trinuclear framework. 2b) demonstrated that an unusual reaction had occurred to give a trimetallic complex, [6]SbF 6 , in which a single Au(I) cation was sandwiched between two Au(III) alkynyl groups.…”

“…In addition to the growing number of synthetic applications of gold complexes in both the +1 and +3 oxidation states, 1 there is clear evidence that binding of two gold atoms to the unsaturated substrate (diauration) plays an important role in catalysis. Indeed, all three binding modes have been proposed within a single catalytic cycle, 6 illustrating the flexibility of digold coordination to support key intermediates in C-C bond forming reactions. 1) are key intermediates in the cyclisation of diynes.…”

“…Repeating the reaction but using CH 2 Cl 2 as solvent for [4], or dissolving isolated [5]SbF 6 in CD 2 Cl 2 , resulted in a colour change from yellow to green, indicating formation of a different product, identified as [6]SbF 6 (Scheme 2). Slow diffusion of Et 2 O into these solutions afforded green crystals suitable for study by X-ray diffraction.…”

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…1368) with the dual catalyst activating system in 1,2-dichloroethane in the presence of alcohols led to the β-substituted naphthalene systems (e.g. 1369) [1242]. The isolated alkynylgold complex reacted with additional gold complex to afford the benzopentalenes, which suggests that these complexes are not involved in naphthalene formation.…”

Gold-Catalyzed Atom-Economical Cascade Reactions of Alkynes for Ring Formation

“…We speculated that a dual activation mechanism through formation of a gold acetylide intermediate would be another possible pathway, where two gold fragments are used for the activation of the terminal alkyne (π activation and σ coordination). However, this possibility was ruled out as the major pathway in collaboration study with the Hashmi group 18 : the reaction of acetylide 24a Au with 2 mol% of IPrAuCl/AgOTf in the presence of EtOH gave monoaurated benzopentalene species 26a (Scheme 9). Even if the reaction of 24a Au with EtOH (1.1 equiv) was carried out in the presence of HBF 4 OEt 2 (1 equiv) without using the gold catalyst, only a trace amount of 25a (4%) was produced.…”