Synthesis of cyclic ethers
The platinum-catalyzed hydroalkoxylation of γ- and δ-hydroxy olefins tolerated various substitution patterns and a number of functional groups including pivaloate and acetate esters, amides, silyl and benzyl ethers, and pendant hydroxyl and olefinic groups.
H. Qian, X. Han, R. A. Widenhoefer, J. Am. Chem. Soc., 2004, 126, 9536-9537.
The reaction of tertiary 1,4- and 1,5-diols with cerium ammonium nitrate at room temperature gives tetrahydrofuran and tetrahydropyran derivatives in high yield and stereoselectivity. Various fragrant compounds have been synthesized using this method.
E. J. Alvarez-Manzaneda, R. Chabouna, E. Alvarez, E. Cabrera, R. Alvarez-Manzaneda, A. Haidour, J. M. Ramos, Synlett, 2006, 1756-1758.
Medium-sized cyclic ethers have been effectively synthesized through intramolecular reductive coupling of dialdehydes in the presence of a hydrosilane and low loadings of AgNTf2 as catalyst at 25°C. The catalytic system is also suitable for the coupling of two different monoaldehydes to provide unsymmetrical ethers. This protocol features broad functional group compatibility and high product diversity.
T. Liang, G. Dong, C. Li, X. Xu, Z. Xu, Org. Lett., 2022, 24, 1817-1821.
The Au(I)-catalyzed intramolecular hydroamination of N-allenyl carbamates was effective for the formation of various cyclic amines. γ-Hydroxy and δ-hydroxy allenes underwent Au-catalyzed intramolecular hydroalkoxylation to form the corresponding oxygen heterocycles in good yield. 2-Allenyl indoles underwent Au-catalyzed intramolecular hydroarylation to form 4-vinyl tetrahydrocarbazoles in good yield.
Z. Zhang, C. Liu, R. E. Kinder, X. Han, H. Qian, R. A. Widenhoefer, J. Am. Chem. Soc., 2006, 128, 9066-9073.
Treatment of 3-[(alkoxycarbonyl)alkyl]-substituted conjugated cycloalkenones with diisobutylaluminum hydride at -78 °C followed by acid quenching furnishes spiro ethers, whereas the corresponding 3-(carboxyalkyl)-substituted cycloalkenones generate spiro lactones upon reaction with sodium borohydride at 30 °C followed by acid quenching.
M.-C. P. Yeh, Y.-C. Lee, T.-C. Young, Synthesis, 2006, 3621-3624.
A combination of Pd(II)/bis-sulfoxide C-H activation and Lewis acid co-catalysis enables the synthesis of chroman, isochroman, and pyran motifs from a wide range of alcohols. Mechanistic studies suggest that the reaction proceeds via initial C-H activation followed by a novel inner-sphere functionalization pathway.
S. E. Ammann, G. T. Rice, M. C. White, J. Am. Chem. Soc., 2014, 136, 10834-10837.
A nucleophilic substitution of alkyl fluorides was achieved in intramolecular reactions with O- and N-nucleophiles. The reaction is influenced by the nature of nucleophiles, the size of the ring to be formed, and the comformational rigidity of the precursors.
L. Zhang, W. Zhang, J. Liu, J. Hu, J. Org. Chem., 2009, 74, 2850-2853.
A highly reactive and confined imidodiphosphorimidate (IDPi) catalyst enables a direct enantioselective synthesis of substituted oxygen heterocycles from lactol acetates and enolsilanes. Various chiral oxygen heterocycles, including tetrahydrofurans, tetrahydropyrans, oxepanes, chromans, and dihydrobenzofurans, were obtained in excellent enantioselectivities.
S. Lee, P. S. J. Kaib, B. List, J. Am. Chem. Soc., 2017, 139, 2156-2159.
A bifunctional aminoboronic acid facilitates intramolecular aza- and oxa-Michael reactions of α,β-unsaturated carboxylic acids. The combination of an arylboronic acid with a chiral aminothiourea enables enantioselective conversions to afford the desired heterocycles in high yields and ee’s (up to 96% ee).
T. Azuma, A. Murata, Y. Kobayashi, T. Inokuma, Y. Takemoto, Org. Lett., 2014, 16, 4256-4259.
Dehydration of 1,6-diols by treatment with BF3·OEt2 in dichloromethane gave tetrahydrobenzoxepines in very good yields, whereas 1,7-diols did not undergo dehydration.
M. Yus, T. Soler, F. Foubelo, Tetrahedron, 2002, 58, 7009-7016.
An efficient and regioselective Yb(OTf)3-promoted palladium-catalyzed oxidative cyclization of γ-heteroalkenyl β-keto amides has been developed. Under simple aerobic condition, various six-, seven-, and eight-membered-ring N- and O-heterocycles were obtained in excellent yield.
K.-T. Yip, J.-H. Li, O.-Y. Lee, D. Yang, Org. Lett., 2005, 7, 5717-5719.
Diastereoselective and Enantioselective Construction of Cyclic Ethers
Stereocontrolled Construction of Cyclic Ethers
Enantioselective Construction of Naturally-Occurring Cyclic Ethers