Copper-catalyzed coupling, aryl ether synthesis

Copper-catalyzed C-O, C-N, and C-S Coupling. While there is an extensive variety of palladium catalysts for C(aryl)-X bond formation (X = 0, N, and S), copper corrqtlexes have recently gained renewed popularity in these coupling processes. Use of the (CuOTf)2. benzene complex allows the formation of diaryl ethers from aryl bromides or iodides and phenols in very good yields (76-93%) (eq 121). The reaction occurs in toluene in the presence of cesium carbonate as the base and a catal)4ic quantity of ethyl acetate whose role is probably to increase the solubility of the copper species. In the case of less reactive phenols, yields can be increased by the addition of a stoichiometric amount of carboxylic acid. A slight modification of these conditions has been used in the key diaryl ether formation in the synthesis of verbenachalcone. ... 

In 2014, a copper and iron co-catalyzed Ullmann coupling of diiodo- and dibromoarenes and diphenols to aryl ether macrocycles was developed. In the presence of Cul (10 mol%) and Fe(acac)3 (10 mol%) with K2CO3 as a base in DMSO at 110 °C, the corresponding macrocycles can be isolated in low to moderate yields. However, a long reaction time (7 days) is required. Li and co-workers developed a palladium-catalyzed Ullmann protocol and applied it to the synthesis of 6,7-dihydro-5H-dibenzo[c,e]azepines and biaiyls. In the presence of Pd(OAc)2 and KOAc, intramolecular or intermolecular Ullmann... 

C-0 Bond Formation. A simple and mild method for the coupling of aryl iodides and aliphatic alcohols catalyzed by copper iodide which does not require the use of aUcoxide bases has been described. The reaction can be performed in neat alcohol or in toluene as solvent with catalytic quantities of Cul and 1,10-phenanthrohne, and 2 equiv of CS2CO3. This methodology was successfully applied to the formation of allyl vinyl ethers with tetramethyl-l,10-phenanthroline as the ligand. iVAl-Dimethyl glycine is also a good ligand for this copper iodide-catalyzed Ullmann-type diaryl ether synthesis between phenols... 

Copper-catalyzed Aryl Ether Formation. Traditional methods for formation of aryl ethers involve stoichiometric Ullmann couplings. A new system was developed exploiting catalytic CuCl and NMI as a ligand. The title compound was chosen due to its similarities to histidine, a common amino acid for binding metals. This methodology was applied to the synthesis of the insecticide diafenthiuron that produced the desired aryl ether in greater than 98% yield compared to 39% reported in current patents (eq 32). ... 

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