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1.
Masahiro Yoshida 《Tetrahedron letters》2004,45(9):1861-1864
Substituted 2,3-dihydrofurans and benzofurans are synthesized by the palladium-catalyzed reaction of 5-methoxycarbonyloxy-3-pentyn-1-ols and 1-(2-hydroxyphenyl)-3-methoxycarbonyloxy-1-propyne with nucleophiles, respectively. Various substituted propargylic carbonates and nucleophiles are efficiently transformed to their corresponding products. Additionally, a reaction using substrates containing a nucleophilic phenoxy group within the same molecule also produces the corresponding dihydrofuran. 相似文献
2.
Treatment of halides 5 with electrophilic alkenes 2 afforded the corresponding dihydrofurans 3 and 4 in the presence of 1, 4-diazabicyclo[2.2.2]octane (DABCO) with good to excellent yields and in a stereoselective manner in most cases. Moreover, the stereoisomers 3 and 4 could be easily transformed each other in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). 相似文献
3.
Morgan Donnard Théophile Tschamber Didier Le NouënSandy Desrat Karen HinsingerJacques Eustache 《Tetrahedron》2011,67(2):339-357
The rearrangement of dihydropyrans and dihydrofurans featuring appending olefins has been studied. The rearranged products bear resemblance with polyunsaturated di- and trisaccharides. Examples of functionalization prior to, or following, rearrangement are provided suggesting that the method should be useful for the synthesis of nonclassical saccharides. This work also illustrates the power of cascade methatetic processes for increasing molecular complexity starting from relatively simple heterocycles. 相似文献
4.
Manganese(III) acetate catalyzed oxidative radical‐addition reactions of α‐dicarbonyl compounds such as methyl acetoacetate ( 6 ), acetylacetone ( 7 ), and dimedone ( 8 ) to the mixture of 1‐ and 2‐phenylcyclohepta‐1,3,5‐triene ( 4 and 5 ) were investigated (Scheme 1). The 1‐phenylcyclohepta‐1,3,5‐triene ( 4 ) formed mainly [2+3] and [4+3] dihydrofuran addition products derived from cycloheptatriene and [2+3] dihydrofuran addition products derived from the norcaradiene structure. The 2‐phenylcyclohepta‐1,3,5‐triene ( 5 ) formed mainly [6+3] dihydrofuran addition products derived from cycloheptatriene and [4+3] dihydrofuran addition products derived from the norcaradiene structure. The structures of isolated products were established by their spectroscopic data (IR, 1H‐ and 13C‐NMR, MS, and elemental analysis) and comparison with literature data. The formation mechanism of the products is discussed. 相似文献
5.
Poly-substituted dihydrofurans and tetrahydrofurans have been synthesized through polymer-supported selenium-induced intramolecular electrophilic cyclization, followed by selenoxide syn-elimination or novel nucleophilic substitution cleavage of selenium resin with good yields and purities. 相似文献
6.
On treatment of N-tosylimines (1) and 4-hydeoxyl- cis-butenyl arsonium salt (5) with KOH in acetonitrile at room temperature, 2–(α-substituted N-tosylaminomethyl)-2, 5-dihydrofurans (4) were obtained in moderate yields. The arsonium salt (5) acts formally as an equivalent of 2,5-dihydrofuran synon. A plausible mechanism was proposed for this new 5-membered cyclization reaction. 相似文献
7.
On treatment of N-tosylimines (1) and 4-hydroxyl-cis-butenyl arsonium salt (5) with KOH in acetonitrile at room temperature, 2-(a-substituted N-tosylaminomethyl)-2,5-dihydrofurans (4) were obtained in moderate yields. The arsonium salt (5) acts formally as an equivalent of 2,5-dihydrofuran synon. A plausible mechanism was proposed for this new 5-membered cyclization reaction. 相似文献
8.
Base Mediated Michael addition of 1,3-dicarbonyl compounds to α-halodicyclopentadienones followed by cyclization of the intermediate Michael adducts leads to novel annulated dihydrofurans as single diastereomers. Such fused dihydrofurans, which are also oxa-triquinanes and oxa-diquinanes, undergo retro-Diels-Alder reaction to give cyclopentadiene-eliminated products in excellent yield. Certain 1,3-dicarbonyl compounds exhibited a different reactivity profile with α-halodicyclopentadienones leading to spiro-cyclopropanes fused to dicyclopentadiene skeleton. 相似文献
9.
The preparation of E-5-(1-bromo-2-aryl-vinyl)-3-methyl-4-nitro-isoxazoles and their reaction with 1,3-dicarbonyl compounds to give cyclopropanes or dihydrofurans is described. 相似文献
10.
Esko Taskinen 《Structural chemistry》2000,11(1):47-53
The geometry optimized structures and total energies of 3-substituted (R) 2,5-dihydrofurans (a) and their isomers, 4-substituted 2,3-dihydrofurans (b), have been determined by ab initio calculations at the MP2/6-31G*//HF/6-31G* level. The nature of the moiety R has a marked effect on the relative total energies of the isomeric forms: at the calculation level cited, the reaction enthalpies for the a b isomerization range from +4.7 kJ mol–1 for R = MeO to –30.5 kJ mol–1 for both R = COOMe and R = NO2. The reaction enthalpies appear to be controlled by the electronic effect of R on the strength of p- conjugation in b. The a isomer has a planar ring, independent of R (excluding NH2), whereas the planarity of b depends on the electronic nature of R: the 2,3-dihydrofuran ring is planar for both R = COOMe and R = NO2, but nonplanar for less conjugation-enhancing substituents. 相似文献