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1.
The reactions of arsonium bromides with (E)-α-trifluoromethylsulfonyl-α,β-unsaturated ketones in the presence of Cs2CO3 or K2CO3 proceeded smoothly under refluxing condition in dichloromethane (DCM) to give the corresponding trifluoromethylated trans-2,3-dihydrofurans in good to excellent yields with high stereoselectivity. 相似文献
2.
Chih-Ching Chen 《Tetrahedron》2008,64(45):10350-10354
In this paper, we report a one-step convergent synthesis of (E)-β-monosubstituted α,β-unsaturated amides 3 from α-sulfonyl acetamide 1 and benzyl bromide derivatives 2. 相似文献
3.
Catalyzed by ammonium acetate, the Knoevenagel reactions of β-keto perfluoroalkanesulfones 1 with aromatic aldehydes 2 afforded α-perfluoroalkanesulfonyl-α,β-unsaturated ketones 4 in moderate to good yields. The possible mechanism for the reactions was proposed. These fluorine-containing α,β-unsaturated ketones, which are electron-poor 1-oxa-1,3-butadienes, could be used in inverse electron demand hetero Diels-Alder (HDA) reaction with electron-rich olefins to give tetrasubstituted dihydropyrans 6 in quantitative yields. 相似文献
4.
Jan Hajduch 《Journal of fluorine chemistry》2008,129(2):112-118
Horner-Emmons fluoroolefination of an aryl aldehyde followed by introduction of a second fluorine via “FBr” addition provides an original approach to the preparation of 1-alkyl-2-aryl-1,2-difluoroethenes. The utility of this procedure is demonstrated by the preparation of (E and Z)-α,β-difluorourocanic acid. 相似文献
5.
Rodríguez-Solla H Concellón C Blanco EG Sarmiento JI Díaz P Soengas RG 《The Journal of organic chemistry》2011,76(13):5461-5465
A chromium-mediated novel synthesis of carbohydrate-derived di- and trisubstituted (E)-α,β-unsaturated esters or amides from a range of dichloroesters or amides and a variety of sugar aldehydes is reported. The process took place with total stereoselectivity and in high yields. A mechanism based on a sequential chromium-promoted aldol-type reaction and a completely stereoselective β-elimination reaction is proposed to explain these results. 相似文献
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7.
Haiming Wang 《Tetrahedron letters》2009,50(19):2200-2203
A class of chiral self-supported catalysts prepared from bis-BINOL ligands and diethyl zinc were successfully applied in the hetereogeneous enantioselective epoxidation of a range of (E)-α,β-unsaturated ketones, affording the corresponding epoxy ketones in high enantioselectivity. The self-supported catalysts were easily recovered from the reaction mixture and were reusable for several consecutive runs. 相似文献
8.
Stereoselective β-elimination in α,α-dichloro-β-hydroxyesters 2 was achieved by using samarium diiodide, yielding (Z)-α-chloro-α,β-unsaturated esters 1. The starting compounds 2 were easily prepared by reaction of the lithium enolate of ethyl dichloroacetate with different aldehydes at −78 °C. A mechanism to explain this process is proposed. 相似文献
9.
(E)-α,β-Unsaturated ketones 1 or esters 2 can be obtained with complete stereoselectivity by reaction of different 2-chloro-3-hydroxy ketones 3 or esters 4 and CrCl2. A comparative study of the results of synthesis of ketones 1 with CrCl2 or samarium is performed. A mechanism to explain both β-elimination reactions has been proposed. 相似文献
10.
C. Wade Downey Smaranda CraciunAna M. Neferu Christina A. ViveloCarly J. Mueller Brian C. SouthallStephanie Corsi Eric W. EtchillRyan J. Sault 《Tetrahedron letters》2012,53(43):5763-5765
β-Sulfonyl enoates may be synthesized through a one-pot two-step sequence from ethyl propiolate with good to excellent selectivity for the Z isomer. Trialkylamines catalyze thioconjugate additions of aryl thiols, and alkoxides catalyze the addition of aliphatic thiols. Addition of meta-chloroperbenzoic acid (mCPBA) and LiClO4 to the reaction mixture provides rapid access to the sulfonyl enoates. Yields of the pure Z isomer range from 51-90%. 相似文献
11.
New polymer-supported phosphonate reagents have been prepared and evaluated for the synthesis of Z-α,β-unsaturated esters. High Z-selectivity was obtained using the reagent having two o-t-BuC6H4 groups. 相似文献
12.
Ming-Zhong Cai Gui-Qin Chen Wen-Yan Hao Dong Wang 《Journal of organometallic chemistry》2007,692(5):1125-1130
Palladium-catalyzed hydrostannylation of acetylenic sulfones 1 in benzene at room temperature gives stereoselectively (E)-α-stannylvinyl sulfones 2 in good yields. (E)-α-Stannylvinyl sulfones 2 are new difunctional group reagents which undergo Stille coupling reactions with alkenyl iodides 3 to afford stereoselectively 1,3-dienyl sulfones 4 in high yields. 相似文献
13.
J.S. Yadav B.V. Subba Reddy G. Narasimhulu N. Sivasankar Reddy P. Janardhan Reddy 《Tetrahedron letters》2009,50(27):3760-64
The α,β-unsaturated compounds undergo smooth conjugate addition with 2-(trimethylsilyloxy)furan (TMSF) in the presence of 10 mol % of iodine under mild and neutral conditions to afford the corresponding γ-substituted butenolides in high yields and with good diastereoselectivity. The use of iodine makes this procedure simple, convenient and cost effective. 相似文献
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E. I. Klimova E. A. Vazquez Lopez T. Klimova M. Martinez Garcia Ortega S. Hernandez L. Ruiz Ramirez 《Russian Journal of General Chemistry》2004,74(11):1757-1762
Ferrocenyltetrahydropyrimidin-2-ones were prepared by reactions of linear and cyclic ,-unsaturated ketones of the ferrocene series with urea in i-PrOH in the presence of t-BuOK. The structures of the compounds prepared were studied by 1H and 13C NMR and IR spectroscopy, and also by single crystal X-ray diffraction.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004, pp. 1887–1893.Original Russian Text Copyright © 2004 by E. Klimova, Lorez, T. Klimova, Garcia, Hernandez, Ramirez.This revised version was published online in April 2005 with a corrected cover date. 相似文献
16.
Iridium phosphinitoxazoline complexes were found to be new efficient catalysts for the asymmetric hydrogenation of arylated α,β-unsaturated ketones. Linear as well as cyclic substrates are hydrogenated with similar success, giving selectivities of up to 99.7% ee. 相似文献
17.
Bis(trimethylsilyl)-tert-butylaldimines 3 react with aldehydes in the presence of zinc bromide at room temperature to give, after hydrolysis, the desired α-alkyl α,β-ethylenic aldehydes in good yield and with very high E stereoselectivity. The reaction was believed to proceed via the α-silyl β-siloxyimines 4. 相似文献
18.
Mallam Venkataiah 《Tetrahedron》2009,65(34):6950-100
A novel stereoselective synthesis of (−)-β-conhydrine is achieved. Stereoselective Grignard reaction of (R)-2,3-O-cyclohexylidine glyceraldehyde with ethyl magnesium bromide, chelation controlled stereoselective Grignard reaction of allyl imine derivative with allyl magnesium bromide, and ring-closing metathesis (RCM) of the diallyl product provides (−)-β-conhydrine in high yield. 相似文献
19.
《Tetrahedron letters》1988,29(32):3895-3898
Anhydrous acidic treatment of E,Z mixtures of α-methyl-α,β-unsaturated imines followed by hydrolysis gives the corresponding aldehydes with ≥ 100:1 E:Z ratios. 相似文献
20.
Two new vitamin D2 analogues, (22Z)-25-(OH)-D2 and (22Z)-1α,25-(OH)2-D2, were serendipitously synthesized from vitamin D2 and using the Julia-Kocienski olefination. 相似文献