Aryl Ethers Synthesis Essay
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Synthesis of aryl ethers
Self-assembled octanuclear copper clusters catalyzed the coupling of aryl iodides with alcohols under mild conditions. Reactions involving low catalyst loadings (0.4%) and tetrahydrofurfuryl alcohol were typically complete in 4-8 h at 110°C using an oil bath or 1-3 h with microwave heating.
G. F. Manbeck, A. J. Lipman, R. A. Stockland, A. L. Freidl, A. F. Hasler, J. J. Stone, I. A. Guzei, J. Org. Chem., 2005, 70, 244-250.
The use of 3,4,7,8-tetramethyl-1,10-phenanthroline (Me4Phen) as a ligand improves the Cu-catalyzed cross-coupling reactions of aryl iodides and bromides with primary and secondary aliphatic, benzylic, allylic, and propargylic alcohols. The relatively mild conditions, tolerate a wide array of functional groups on both the electrophilic and nucleophilic coupling partners.
R. A. Altman, A. Shafir, P. A. Lichtor, S. L. Buchwald, J. Org. Chem., 2008, 73, 284-286.
In an efficient and mild copper-catalyzed ether formation from aryl halides and aliphatic alcohols, the key to a successful coupling is the use of lithium alkoxide, directly or in situ generated by lithium tert-butoxide, and the corresponding alcohol as solvent.
J. Huang, Y. Chen, J. Chan, M. L. Ronk, R. D. Larsen, M. M. Faul, Synlett, 2011, 1419-1422.
Ullmann-type coupling reactions of aryl iodides and aliphatic alcohols occur at 110 °C with N,N-dimethylglycine as the ligand, giving aryl alkyl ethers in high yields.
H. Zhang, D. Ma, W. Cao, Synlett, 2007, 243-246.
A simple and mild coupling method of aryl iodides and aliphatic alcohols, which does not require alkoxide bases, can be performed in neat alcohol or toluene as solvent. An optically active benzylic alcohol underwent the reaction with complete retention of configuration.
M. Wolter, G. Nordmann, G. E. Job, S. L. Buchwald, Org. Lett., 2002, 4, 973-976.
Transition-metal-free arylation of tertiary alcohols with ortho-substituted diaryliodonium salts enables the synthesis of tertiary alkyl aryl ethers of previously unprecedented steric congestion. Cyclic and acyclic aliphatic, benzylic, allylic, and propargylic tertiary alcohols as well as primary and secondary fluorinated alcohols can be converted.
E. Lindstedt, E. Stridfeldt, B. Olofsson, Org. Lett., 2016, 18, 4234-4237.
An arylation of allylic and benzylic alcohols with diaryliodonium salts yields alkyl aryl ethers under mild and metal-free conditions. Phenols are arylated to diaryl ethers in good to excellent yields. The reaction employs diaryliodonium salts and sodium hydroxide in water at low temperature, and avoids the use of excess amounts of the coupling partners.
E. Lindstedt, R. Ghosh, B. Olofsson, Org. Lett., 2013, 15, 6070-6073.
Palladium-catalzyed reactions of aryl halides including activated, nonactivated, and (hetero)aryl bromides as well as aryl chlorides with primary alcohols gave the corresponding alkyl aryl ethers in high yield in the presence of a bulky di-1-adamantyl-substituted bipyrazolylphosphine ligand. Functionalizations of primary alcohols in the presence of secondary and tertiary alcohols proceed with excellent selectivity.
S. Gowrisankar, A. G. Sergeev, P. Anbarasan, A. Spannenberg, H. Neumann, M. Beller, J. Am. Chem. Soc., 2010, 132, 11592-11598.
A general Pd-catalyzed coupling of methanol with (hetero)aryl halides proceeds under mild conditions with a wide range of aryl and heteroaryl halides to give methyl aryl ethers in high yield.
C. W. Cheung, S. L. Buchwald, Org. Lett., 2013, 15, 3966-3969.
A one-pot method for the preparation of alkyl aryl ethers from aryl halides and the preparation of substituted benzofurans via a Pd-catalyzed phenol formation/cyclization protocol starting from 2-chloroaryl alkynes are described.
K. W. Anderson, T. Ikawa, R. E. Tundel, S. L. Buchwald, J. Am. Chem. Soc., 2006, 128, 10694-10695.
A palladium-catalyzed synthesis of aryl tert-butyl ethers from a variety of unactivated aryl bromides or chlorides is described. The ether products, which are precursors to phenols, are obtained in very good yield in the presence of air-stable dialkylphosphinobiphenyl ligands.
C. A. Parrish, S. L. Buchwald, J. Org. Chem, 2001, 66, 2498-2500.
An efficient synthetic route to a range of macrocyclic aryl ether ketone and sulfone oligomers containing a cross-linkable diphenylacetylene moiety in the backbone is described. This new class of macrocyclic oligomers, obtained in excellent yield, is prepared by an aromatic nucleophilic substitution reaction from the potassium salt of bis(3-hydroxyphenyl)acetylene and activated difluoro-monomers. Detailed structural characterization of these novel oligomers by the combination of n.m.r. and matrix assisted laser desorption and ionization-time of flight-mass spectroscopy (MALDI-TOF-MS) confirms their cyclic nature; and the compositions of these macrocyclic oligomers are provided by g.p.c. and reverse-phase gradient h.p.l.c. analyses. MALDI-TOF-MS is a unique tool for the determination and the proof of the cyclic nature of random co-cyclic oligomers, and also provides answers to the possible combinations of monomer units in the cyclic olgiomeric components for the random co-cyclic oligomers. All macrocyclic oligomers are semicrystalline with Tm varying from 267 to 370°C and when the oligomers are heated an exothermic reaction, resulting from reaction of the acetylene units, occurs in the range of 340–470°C and the macrocyclics undergo a cross-linking reaction. Polymerization of the lower melting macrocyclic oligomers at 280–300°C, in the presence of a nucleophilic initiator, led to the formation of high molecular weight insoluble materials with limited cross-linking reactions taking place. The resulting polymers can be further cross-linked at 340°C with a Tg increase up to 100°C or complete disappearance of Tgs.