Categories: Synthesis of O-Heterocycles
Synthesis of 2,3-Dihydrofurans
Neopentyl phosphine ligands promote Heck couplings with aryl bromides at ambient temperature. In the Heck coupling of 2,3-dihydrofuran di-tert-butylneopentylphosphine (DTBNpP) promotes isomerization to a much greater extent than trineopentylphosphine (TNpP). A similar complementary product selectivity is seen in the Heck coupling of cyclopentene.
M. G. Lauer, M. K. Thompson, K. H. Shaughnessy, J. Org. Chem., 2014, 79, 10837-10848.
A chemoselective intramolecular hydroamination and hydroalkoxylation of readily available α-allenic amines and alcohols provides valuable 2,3-dihydropyrroles and 2,3-dihydrofurans in the presence of low amounts of an air and moisture stable iron catalyst. The mild reaction conditions allow fthe hydrofunctionalization of a wide range of allenes bearing different functional groups in good yields in the absence of base or any sensitive additives.
O. El-Sepelgy, A. Brzozowska, J. Sklyaruk, Y. K. Jang, V. Zubar, M. Rueping, Org. Lett., 2018, 20, 696-699.
An oxyboration reaction, that employs B-O bonds as addition partners to C=C bonds, provides borylated dihydrofurans and isochromenes. The reaction produces exclusively one borylated regioisomer, in contrast to syntheses of borylated heterocycles via C-H activation.
K. N. Tu, C. Gao, S. A. Blum, J. Org. Chem., 2018, 83, 11204-11217.
A planar-chiral bipyridine ligand enables diastereo- and enantioselective copper-catalyzed [4+1] cycloadditions of enones with diazo compounds to produce highly substituted 2,3-dihydrofurans. The method is applied to a catalytic asymmetric synthesis of a deoxy-C-nucleoside.
S. Son, G. C. Fu, J. Am. Chem. Soc., 2007, 129, 1046-1047.
The reaction between Corey ylide and α,β-unsaturated ketones enables a straightforward, efficient, and reliable synthesis of valuable 2,3-dihydrofurans. The reaction offers use of simple and commercially available starting materials, mild reaction conditions, and scalability.
A. O. Chagarovsky, E. M. Budynina, O. A. Ivanova, E. V. Villemson, V. B. Rybakov, I. V. Trushkov, M. Y. Melnikov, Org. Lett., 2014, 16, 2830-2833.
A highly chemo-, regioselective, and efficient Pd(0)-catalyzed coupling-cyclization of 2-(2',3'-allenyl)acetylacetates with organic halides using K3PO4 as base in DMF afforded 4,5-dihydrofuran derivatives in good yields.
S. Ma, Z. Zheng, X. Jiang, Org. Lett., 2007, 9, 529-531.
A chiral ferrocene/benzimidazole-based P,N-ligand enables a highly enantioselective palladium-catalyzed [3 + 2] cycloaddition of propargylic esters with β-ketoesters providing 2,3-dihydrofurans bearing an exocyclic double bond at the 3-position in good yields and with high enantioselectivities. This protocol tolerates a broad range of functional groups in both propargylic esters and β-ketoesters.
Y. Zhou, F.-L. Zhu, Z.-T. Liu, X.-M. Zhou, X.-P. Hu, Org. Lett., 2016, 18, 2734-2737.
A chiral phosphine-catalyzed enantioselective [1 + 4] annulation of Morita-Baylis-Hillman carbonates with β,γ-unsaturated α-keto esters and α,β-unsaturated ketones provides a wide range of optically active 2,3-dihydrofurans in high yields with excellent asymmetric induction via a Michael alkylation process.
Y. Cheng, Y. Han, P. Li, Org. Lett., 2017, 19, 4774-4777.
A new method for the synthesis of 2,3-dihydrofurans from readily available starting enones and pyridinium salts has been developed. This protocol can provide a novel and effective methodology for the preparation of 2,3-dihydrofurans in a stereoselective fashion. A one-pot process was also developed, in which the pyridinium salts were generated in situ from corresponding halides.
S. Xue, L. He, Y.-K. Liu, K.-Z. Han, Q.-X. Guo, Synthesis, 2006, 666-674.
An olefin metathesis/double bond migration sequence of allyl ethers to cyclic enol ethers is catalyzed by first and second generation Grubbs' catalysts. These ruthenium carbene complexes were activated to catalyze the double bond migration by additioin of hydride sources, such as NaH or NaBH4.
B. Schmidt, Eur. J. Org. Chem., 2003, 816-819.
An organo/copper cooperative system enables a catalytic asymmetric decarboxylative [3 + 2] cycloaddition reaction of ethynylethylene carbonates with malononitrile to provide optically active polysubstituted dihydrofurans in good yields with high levels of enantioselectivities. The presence of the cyano group and the terminal alkynyl provides a wide scope for further structural transformations.
Y.-C. Zhang, B.-W. Zhang, R.-L. Geng, J. Song, Org. Lett., 2018, 20, 7907-7911.