Ligand-free highly effective iron/copper co-catalyzed formation of dimeric aryl ethers or sulfides

Abstract

Highly selective coupling of diiodoarenes with phenols or phenthiols can be performed by using a low-cost, benign character and readily available Fe/Cu catalytic system in the absence of ligands. It is noteworthy that the desired dimeric aryl ethers or sulfides could be obtained in high yields by coupling between diiodoarenes and phenols, or diphenols with aryl iodides.

Metal‐Free Arylation of Oxygen Nucleophiles with Diaryliodonium Salts

“…High yields of a range of diaryl ethers are often obtained, but heteroaromatic or ortho ‐substituted coupling partners are often challenging substrates. [9, 10] Iron/copper co‐catalyzed systems have recently been reported 11…”

Chemoselective and ligand-free synthesis of diaryl ethers in aqueous medium using recyclable alumina-supported nickel nanoparticles

“…As before, the reactions went fine with both 2-bromo-as well as 2-chloropyridines. 3-Chloropyridine, which is generally less responsive towards nucleophilic substitution, also reacted well with phenol and ocresol under the present condition and afforded the corresponding 3-aryloxypyridines in good yield (entries [20][21]. It is important to note that 3-aryloxypyridines and their N-oxides demonstrate diverse pharmacological properties.…”

“…9,10 The most straightforward way to synthesise diaryl ethers is either palladium or copper catalysed coupling reaction between aryl halides and phenols. The harsh conditions of classical Ullmann synthesis have limitations due to involvement of stoichiometric amounts of copper reagents with some extra ligands, [11][12][13][14][15][16][17][18][19][20] requirement of high temperatures along with long reaction time, 11,13-20-22 and use of moisture sensitive, costly base 11,[13][14][15][16]18,19,22 as well as employment of inert atmosphere. [11][12][13]15,16,18,[21][22][23][24] For this reason, immense efforts have been spent in past few years for the discovery of more attractive and utilitarian arylation methods.…”

The Application of Copper/Iron Cocatalysis in Cross-Coupling Reactions

“…CuFe 2 O 4 cocatalyzed Ullmann-type C-O couplings reported by Xu. [24] Scheme 11. CuFe 2 O 4 cocatalyzed S-arylations between halides and thiols and diphenyl disulfide reported by Nageswar.…”

“…Inspired by these findings, Mao and coworkers then developed a very effective iron/copper cocatalyzed methodology for the formation of dimeric aryl ethers or sulfides without the assistance of ligands (Scheme 9). [24] In this catalyst system, Fe(acac) 3 was combined with one equivalent of CuI to achieve high efficacy for the coupling of a variety of dihalide arenes with phenols or phenthiols, and desired dimeric aryl ethers or sulfides were formed and subsequently isolated in excellent yields. Except for 1,4-diphenol, other diphenols such as 2,2 0 -biphenol and BINOL were also transformed smoothly to the corresponding diaryl ethers in excellent yields, with preservation of ee values.…”