Categories: C-O Bond Formation >
Synthesis of ethers
Nucleophilic fluorination using CsF or alkali metal fluorides was completed in short reaction time in the presence of [bmim][BF4] affording the desired products without any byproducts. Facile nucleophilic substitutions such as halogenations, acetoxylation, nitrilation, and alkoxylations in the presence of ionic liquids provided the desired products in good yields.
D. W. Kim, C. E. Song, D. Y. Chi, J. Org. Chem., 2003, 68, 4281-4285.
A new synthetic method for the preparation of potassium organotrifluoroborates through nucleophilic substitution of potassium bromo- and iodomethyltrifluoroborates is described. Potassium halomethyltrifluoroborates have been prepared via in situ reaction of n-BuLi with dibromo- and diiodomethane, respectively, in the presence of trialkyl borates, followed by treatment with KHF2.
G. A. Molander, J. Ham, Org. Lett., 2006, 8, 2031-2034.
A novel electrolytic system for non-Kolbe electrolysis based on the acid-base reaction between carboxylic acids and solid-supported bases in MeOH provide the corresponding methoxylated products in excellent yields. The acid-base reaction between carboxylic acids and solid-supported bases preferentially takes place to reduce the cell voltage in MeOH.
T. Tajima, H. Kurihara, T. Fuchigami, J. Am. Chem. Soc., 2007, 129, 6680-6681.
An efficient method chemoselectively converts benzyl alcohols into their methyl or ethyl ethers in the presence of aliphatic or phenolic hydroxyl groups using 2,4,6-trichloro-1,3,5-triazine (TCT) and dimethyl sulfoxide in methanol or ethanol.
L. Sun, Y. Guo, G. Peng, C. Li, Synthesis, 2008, 3487-3488.
A gold-catalyzed, microwave protocol activates alcohols through an intermolecular, SN1-type reaction to directly form unsymmetrical ethers and Cbz-protected amines in good yields. This reaction is highly reproducible and tolerates moisture.
A. R. S. Vinson, V. K. Davis, A. Arunasalam, K. A. Jesse, R. E. Hamilton, M. A. Shattuck, A. C. Hu, R. G. Iafe, A. G. Wenzel, Synlett, 2015, 26, 765-770.
An efficient intermolecular conjugate addition of various primary and secondary alcohols to unsaturated ketones and esters is catalyzed by the free carbene derived from IMes·HCl. No oligomerization is observed under these mild conditions. In addition to reactions with activated alkenes, IMes catalyzes the formation of vinyl ethers through the 1,4-addition of alcohols to ynones.
E. M. Phillips, M. Riedrich, K. A. Scheidt, J. Am. Chem. Soc., 2010, 132, 13179-13181.
The combination of a copper-catalyzed C-O coupling reaction with a subsequent Claisen rearrangement allowed the generation of two adjacent quarternary stereocenters in a one-pot domino process. Furthermore, an experimentally simple stereoselective synthesis of of vinyl ethers is delineated using the same catalyst system.
G. Nordmann, S. L. Buchwald, J. Am. Chem. Soc., 2003, 125, 4978-4979.
A Pd[BiPhePhos] catalyst enables the use nonactivated phenols as nucleophiles in the allylation of nonderivatized allylic alcohols to generate allylated phenolic ethers in very good yields with water as the only byproduct. The kinetically favored O-allylated products are formed exclusively over the thermodynamically favored C-allylated products.
T. Rukkijakan, S. Akkarasamiyo, S. Sawadjoon, J. S. M. Samec, J. Org. Chem., 2018, 83, 4099-4104.
A stereospecific and stereoselective, copper-promoted coupling of vinyl pinacol boronate esters and alcohols allows the synthesis of enol ethers in very good yields, is compatible with various functional groups, and occurs at room temperature. Cupric acetate is the copper source, and triethylamine buffer is used to prevent protodeboration.
R. E. Shade, A. M. Hyde, J.-C. Olsen, C. A. Merlic, J. Am. Chem. Soc., 2010, 132, 1202-1203.
Using commercially available Ph3PAuCl and readily prepared, benign arylsilanes, a gold-catalyzed oxyarylation of alkenes proceeds smoothly in air. The oxidant, Selectfluor, not only facilitates entry to the Au(I/III) manifold but also provides a fluoride anion for silane activation, thereby avoiding the need for addition of a stoichiometric base.
L. T. Ball, M. Green G. C. Lloyd-Jones, C. A. Russel, Org. Lett., 2010, 12, 4724-4727.
A microwave-assisted, chemoselective and efficient method for the cleavage of silyl ethers is catalyzed by Selectfluor. A wide range of TBDMS-, TIPS-, and TBDPS-protected alkyl silyl ethers can be chemoselectively cleaved in high yield in the presence of aryl silyl ethers. In addition, the transetherification and etherification of benzylic hydroxy groups in alcoholic solvents is observed.
S. T. A. Shah, S. Singh, P. J. Guiry, J. Org. Chem., 2009, 74, 2179-2182.
A nickel(0) triethyl phosphite complex promotes the reaction of allylic acetates with thiols to produce allylic sulfides with retention of configuration without allylic rearrangement. A similar reaction of allylic acetates with alcohols and phenols also proceeds with retention of regio- and stereochemistry.
Y. Yatusmonji, Y. Ishida, A. Tsubouchi, T. Takeda, Org. Lett., 2007, 9, 4603-4606.
A wide range of ynol ethers can be prepared via displacement at an sp center. The same protocol can be applied to the synthesis of synthetically useful thioynol ethers. This reaction, which generates highly functionalized, heteroatom-substituted alkynes, involves radical intermediates.
V. J. Gray, J. Cuthbertson, J. D. Wilden, J. Org. Chem., 2014, 79, 5869-5874.
The hydroalkoxylation of allenes with alcohols proceeds smoothly in the presence of a catalytic amount of Ph3PAuNO3 and H2SO4 to give allylic ethers in good yields and high regio- and stereoselectivity.
D.-M. Cui, K.-R. Yu, C. Zhang, Synlett, 2009, 1103-1106.
A mild method for the trimethylsilyl trifluoromethanesulfonate (TMSOTf) catalyzed one-pot synthesis of homoallyl ethers from aldehydes has been developed in the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([bmim] [OTf]). The advantages of this method include the use of a recyclable ionic liquid, facile product isolation without employing excess organic solvent and elimination of an aqueous waste stream.
P. W. Anzalone, R. S. Mohan, Synthesis, 2005, 2661-2663.
A general, Ir(I)-catalyzed enantioselective decarboxylative allylic etherification of aryl allyl carbonates provides aryl allyl ethers with high stereoselection.
D. Kim, S. Reddy, O. V. Singh, J. S. Lee, S. B. Kong, H. Han, Org. Lett., 2013, 15, 512-515.
Chiral phosphine-catalyzed coupling of two readily available partners, γ-aryl-substituted alkynoates and alcohols, under mild conditions enables the enantioselective synthesis of benzylic ethers via internal redox reaction of the alkynoate partner.
D. T. Ziegler, G. C. Fu, J. Am. Chem. Soc., 2016, 138, 12069-12072.
A Pd-catalysed termolecular allenylation cascade followed by a Ru catalysed RCM process affords a diverse range of Δ3-aryl/heteroaryl substituted five-seven membered nitrogen and oxygen heterocycles.
H. A. Dondas, B. Clique, B. Cetinkaya, R. Grigg, C. Kilner, J. Morris, V. Sridharan, Tetrahedron, 2005, 61, 10652-10666.
p-Toluenesulfonic acid efficiently catalyzes direct nucleophilic substitutions of the hydroxy groups of propargylic alcohols with a large variety of carbon- and heteroatom-centered nucleophiles. Reactions can be conducted under mild conditions and in air without the need for dried solvents.
R. Sanz, A. Martinez, J. M. Alvarez-Gutierrez, F. Rodriquez, Eur. J. Org. Chem., 2006, 1383-1386.
A general and efficient FeCl3-catalyzed substitution reaction of propargylic alcohols with carbon- and heteroatom-centered nucleophiles such as allyl trimethylsilane, alcohols, aromatic compounds, thiols, and amides, forms new C-C, C-O, C-S and C-N bonds.
Z.-P. Zhan, J.-L. Yu, Y.-Y. Cui, R.-F. Yang, W.-Z. Yang, J.-P. Li, J. Org. Chem., 2006, 71, 8298-8301.
An economic and practical transformation from secondary alkyl-substituted propargyl acetates to a variety of nucleophilic substitution products is catalyzed by inexpensive InCl3. High yields and excellent chemoselectivity were obtained. Five-, six-, and seven-membered propargyl cycloethers were also successfully constructed.
M. Lin, L. Hao, X.-t. Liu, Q.-z. Chen, F. Wu, P. Yan, S.-x. Xu, X.-l. Chen, J.-j. Wen, Z.-p. Zhan, Synlett, 2011, 665-670.
The preparation of diverse β-chloroethers, β-chloroacetates, and chlorohydrins is efficiently achieved under mild conditions by reaction of alkenes with trichloroisocyanuric acid in alcohols, acetic acid or aqueous acetone, respectively.
G. Fonseca Mendonça, A. Manzolillo Sanseverino, M. C. S. de Mattos, Synthesis, 2003, 45-48.
The reaction between ethynylbenziodoxol(on)es (EBXs) and phenols driven by visible light provides (Z)-2-iodovinyl phenyl ethers with excellent regio- and stereoselectivity. The (Z)-2-iodovinyl phenyl ether products can be further stereospecifically functionalized to form trisubstituted alkenes, demonstrating the potential of these products en route to chemical complexity.
B. Liu, C.-H. Lim, G. M. Miyake, J. Am. Chem. Soc., 2018, 140, 12829-12835.