Categories: C-O Bond Formation >
Synthesis of diaryl ethers
The scope and generality of Pd-catalyzed diaryl ether formation has been improved allowing the coupling of electron-deficient aryl halides almost without any restrictions. The role of the ligand bulk in these C-O bond-forming reactions is discussed.
C. H. Burgos, T. E. Barder, X. Huang, S. L. Buchwald, Angew. Chem. Int. Ed., 2006, 45, 4321-4326.
Functionalized 1,3-dialkylimidazolinium salts as precursors for N-heterocyclic carbenes have been applied in the palladium-catalyzed synthesis of diaryl ethers. An efficient catalyst system was prepared in situ from Pd(OAc)2, a 1,3-dialkylimidazolinium bromide, and NaH.
M. Akkoça, N. Gürbüza, E. Çetinkayab, I. Özdemir, Synlett, 2008, 1781-1784.
Low catalytic amounts of CuI and Fe(acac)3 effectively promote a C-O cross-coupling reaction in the presence of K2CO3 as the base. A serious of diaryl ethers with different substitutents can be synthesized in very good yields. This efficient and economic method is attractive for applications on an industrial scale.
Y. Liu, S. Zhang, Synlett, 2011, 268-272.
The arylation of N-H and O-H containing compounds at room temperature with phenylboronic acids is promoted in the presence of cupric acetate and a tertiary amine. Substrates include phenols, amines, anilines, amides, imides, ureas, carbamates, and sulfonamides.
D. M. T. Chan, K. L. Monaco, R.-P. Wang, M. P. Winteres, Tetrahedron Lett., 1998, 39, 2933-2936.
Mild and metal-free conditions allow a fast and high-yielding synthesis of diaryl ethers - including bulky ortho-substituted diaryl ethers, which are difficult to obtain by metal-catalyzed protocols. Halo-substituents, racemization-prone amino acid derivatives, and heteroaromatics are also tolerated. The methodology is expected to be of high utility in the pharmaceutical industry.
N. Jalalian, E. E. Ishikawa, L. F. Silwa, Jr., B. Olofsson, Org. Lett., 2011, 13, 1552-1555.
An efficient, mild and transition-metal-free N-arylation of amines, sulfonamides, and carbamates and O-arylation of phenols and carboxylic acids has been achieved by using various o-silylaryl triflates in the presence of CsF.
Z. Liu, R. C. Larock, J. Org. Chem., 2006, 71, 3198-3209.
1,1,1-Tris(hydroxymethyl)ethane as a New, Efficient, and Versatile Tripod Ligand for Copper-Catalyzed Cross-Coupling Reactions of Aryl Iodides with Amides, Thiols, and Phenols
Y.-J. Chen, H.-H. Chen, Org. Lett., 2006, 8, 5609-5612.
Copper-catalyzed Ullmann-type diaryl ether synthesis can be performed at 90°C using either aryl iodides or aryl bromides as the substrates under the assistance of N,N-dimethylglycine.
D. Ma, Q. Cai, Org. Lett., 2003, 5, 3799-3802.
Catalyst-free direct coupling of phenols to electron-deficient aryl halides through SNAr-based addition reactions gave diaryl ethers in very good yields within 5-10 min in refluxing DMSO with assistance of microwave irradiation.
F. Li, Q. Wang, Z. Ding, G. Tao, Org. Lett., 2003, 5, 2169-2171.
Diaryl ethers are readily synthesized in high yield at room temperature through the copper(II)-promoted coupling of arylboronic acids and phenols. The reaction is tolerant of a wide range of substituents on both coupling partners. These reaction conditions permit the racemization-free arylation of phenolic amino acids.
D. A. Evans, J. L. Katz, T. R. West, Tetrahedron Letters, 1998, 39, 2937-2940.
With either 1.0 or 0.10 equivalent of DBU, smooth desilylation of various aryl silyl ethers was accomplished selectively in the presence of base-sensitive groups such esters and alkyl silyl ethers. A direct transformation of aryl silyl ethers into biaryl ethers was possible through tandem desilylation and SNAr reaction with activated aryl fluorides.
C.-E. Yeom, H. W. Kim, S. Y. Lee, B. M. Kim, Synlett, 2007, 146-150.