A General and Mild Ullmann-Type Synthesis of Diaryl Ethers

Abstract

[reaction: see text] An efficient method for the synthesis of diaryl ethers under particularly mild conditions is described. Inexpensive ligands were found to greatly accelerate the Ullmann-type coupling of aryl bromides or iodides with phenols. A series of diaryl ethers were obtained with excellent yields in acetonitrile in the presence of Cs(2)CO(3) and catalytic copper(I) oxide. The reaction tolerates substrates with unfavorable substitution patterns, such as sterically hindered coupling partners or electron-rich aryl halides.

Graphene-oxide-supported CuAl and CoAl layered double hydroxides as enhanced catalysts for carbon-carbon coupling via Ullmann reaction

“…Cu and Co particle size can play an important role in the catalytic activity as reported by Gedanken [41]. As observed previously in our group [22] the precipitation of LDH onto graphene oxide leads to a smaller particle size if compared with the unsupported LDH due to a nucleation effect.…”

“…In principle, this reaction requires harsh reaction conditions, such as large excess of phenols, high temperatures (>200 °C) and at least stoichiometric amounts of copper, which result in the production of undesirable chemical waste [40]. Besides, most of the Cu based catalysts need an extra base and/or require long reaction times [41,42]. As an alternative palladium, gold and nickel based catalysts have been introduced [43][44][45][46].…”

A family of ligand and anion dependent structurally diverse Cu(ii) Schiff-base complexes and their catalytic efficacy in an O-arylation reaction in ethanolic media

“…Cheap K 2 CO 3 showed a satisfactory yield and was chosen for the O-arylation reaction (entry 14). The isolated yield increased sharply with the increase of reaction temperature (entries [14][15][16]. The copper concentration in the reaction mixture was another important factor to investigate.…”

Aminophenols as Efficient Ligand for Copper-Catalyzed Ullmann-type Synthesis of Diaryl Ethers

“…The results clearly revealed that an electron-withdrawing group in the aryl bromides favored the coupling reactions (Table 4, entries 24-29 vs 1-4, 10), however an electron-releasing group in the aryl bromides went against the coupling reactions. For example 4-methylbromobenzene could be coupled with phenol to give the products in 59-85% yields (Table 4, entries [11][12][13][14][15][16][17][18], yet aryl bromides with electron-withdrawing substituents, e.g. 2-acetylphenyl bromide, afforded the corresponding products in 86-95% yields (Table 4, entries 24-25, 27-28) with the exception of 4-cyanophenol, which led to a low yield (56%) for the coupling reaction (Table 4, entry 29).…”