Hydrophenoxylation of Alkynes by Cooperative Gold Catalysis

Abstract

Zweifach: Die Titelmethode liefert Arylvinylether in hohen Ausbeuten, in kurzer Reaktionszeit, mit Z‐Stereospezifität und guten Regioselektivitäten. Einblicke in den Reaktionsmechanismus betonen die Rolle von [{Au(NHC)}2(μ‐OH)][BF4] (NHC=N‐heterocyclisches Carben) als Lewis‐Säure [Au(NHC)][BF4] und als Brønsted‐Base [Au(NHC)(OH)] – zwei Goldeinheiten, die synergistisch wirken.

Acid, silver, and solvent-free gold-catalyzed hydrophenoxylation of internal alkynes

“…Catalyst 1 gave a slightly higher yield of the addition product, but 7 was more selective. The regioselectivity of the reaction using our arylgold precatalysts is the opposite of what Sahoo found using his catalyst system [1] and is similar to the regioselectivity found by Nolan using his hydroxide bridged precatalysts [5]. …”

“…The use of gold compounds to promote hydroelementation reactions has grown tremendously over the past few years [1–5]. Using this approach, a host of different organic substrates have been successfully functionalized.…”

“…Using this approach, a host of different organic substrates have been successfully functionalized. Despite the intense interest in this chemistry the addition of phenols to internal alkenes has rarely been investigated [1,5]. Recently, Sahoo reported the hydrophenoxylation of alkynes using a multicomponent catalyst comprised of AuCl 3 , JohnPhos as the supporting ligand, and various silver/potassium salts as promoters [1].…”

Gold Catalysis in (Supra)Molecular Cages to Control Reactivity and Selectivity

“…In a collaboration, Bergman, Raymond and Toste used the anionic Ga 4 L 6 cage to encapsulate the gold phosphine complex [Au(PMe 3 )Br]. [41] As the cage encapsulates cationic species, the bromide ion dissociates upon inclusion, leaving the more active complex [Au(PMe 3 )] + inside the cage. This encapsulated species catalyzed the intramolecular hydroalkoxylation of an allenol in 48 % yield in 18 hours, whereas the non-encapsulated [Au(PMe 3 )Br] gave only 11 % yield after this time (Scheme 6).…”

[Au]/[Pd] Multicatalytic Processes: Direct One‐Pot Access to Benzo[c]chromenes and Benzo[b]furans

“…We have recently reported that a digold catalyst, [{Au(IPr)} 2 -(m-OH)][BF 4 ] (1), could mediate the addition of phenols to un-activated internal alkynes through a dual activation mechanism. [6] This reaction possesses several advantages compared to the previous state-of-the-art, such as the use of milder reaction conditions, lower catalyst loadings, higher turnover numbers (TON) and turnover frequencies (TOF). We continue to be interested in the development of highly efficient and environmentally benign catalytic methodologies for the synthesis of organic molecules; therefore, we sought to combine the advantages offered by an eco-friendly solvent-free protocol, and the atom-and step-economy of sequential strategies.…”