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1.
Fanny Valleix 《Tetrahedron》2005,61(31):7420-7424
The copper-amidophosphane-catalyzed asymmetric addition reaction of dialkylzinc reagents with β-aryl and β-alkylnitroalkenes afforded the corresponding nitroalkanes with moderate to good enantioselectivities (54-80% ee). The performance was highly dependent on the reaction procedure where the addition of nitroalkene to the mixture of copper-amidophosphane and dialkylzinc gave higher ee than the addition of dialkylzinc to a mixture of copper-amidophosphane and nitroalkene. 相似文献
2.
Anthony J. Pearson John D. Protasiewicz James Updegraff Ming Zhang 《Tetrahedron letters》2007,48(31):5569-5572
Conjugate addition reactions of Grignard reagents with cyclopentadienones having trimethylsilyl groups at the α and α′ positions, and 1-hydroxyethyl substitutents at the β and β′ positions, are reported; excellent stereoselectivity was observed and the relative stereochemistry of three of the products was determined by X-ray methods. 相似文献
3.
Amer El-Batta 《Tetrahedron letters》2007,48(10):1761-1765
The presence of catalytic quantities of the copper(I) iodide dimethyl sulfide complex {(CuI)4(SMe2)3} with alkenyl-alkylzincate reagents allows for the complete chemoselective 1,4-addition of various alkenyl groups to a number of α,β-unsaturated carbonyl compounds in CH2Cl2 at +35 °C. The 1,4-addition of the mixed vinylzincate reagent is more efficient than the corresponding vinylzirconocene reagent in CH2Cl2 or THF. By employing CH2Cl2 as a medium, the asymmetric copper-catalyzed addition of the vinyl groups to α,β-unsaturated imides is facilitated by the presence of TMSOTf to give excellent yields and up to 95:5 diastereomeric ratios (dr). 相似文献
4.
Herein, we report efficient catalysts based on phosphoramidites for the asymmetric copper-catalyzed conjugate addition of Grignard reagents to acyclic α,β-unsaturated ketones. A variety of Grignard reagents can be added to aliphatic and aromatic acyclic enones with good yields and moderate to good enantioselectivities. 相似文献
5.
G.S.C. Srikanth Author Vitae Author Vitae 《Tetrahedron》2005,61(44):10377-10441
6.
Weicheng Zhang 《Tetrahedron letters》2005,46(36):6087-6090
A series of spirocyclic phosphoramidite ligands 6-9 with different substituents on the amine moiety were synthesized from the chiral spirocyclic diol (R)-5. These monodentate ligands have been applied in copper-catalyzed conjugate addition of diethylzinc to cyclic enones. Excellent enantioselectivities (up to 99% ee) can be achieved by the use of ligand (R,S,S)-9 bearing stereochemically matched structure derived from the C2-symmetric (S,S)-bis(α-methylbenzyl)amine. 相似文献
7.
The asymmetric syntheses of novel dihydroxyhomoprolines have been achieved using the doubly diastereoselective conjugate additions of the antipodes of lithium N-benzyl-N-(α-methylbenzyl)amide to a set of four chiral α,β-unsaturated esters (derived from d-pentoses) as one of the key steps. A full account of the diastereoselectivity observed in these conjugate additions is presented and the stereochemical outcomes of these reactions have been established unambiguously via a combination of hydrogenolytic chemical correlation and single crystal X-ray diffraction analyses. A tandem hydrogenolysis/intramolecular reductive amination reaction was then used to create the corresponding enantiopure pyrrolidines, providing access to (2′S,3′S,4′R)-dihydroxyhomoproline and (2′S,3′R,4′S)-dihydroxyhomoproline after deprotection. 相似文献
8.
Quan Lan 《Tetrahedron letters》2007,48(27):4675-4678
Asymmetric conjugate addition of α-substituted-α-cyanoacetates to acetylenic ketones has been achieved with high enantioselectivity and moderate E/Z selectivity under the influence of our recently designed, binaphthyl-modified 3,5-bis[3,5-bis(trifluoromethyl)phenyl]phenyl substituted phase transfer catalyst. 相似文献
9.
Enantioselective copper-catalyzed conjugate borylation of α,β-unsaturated phosphonates with bis(pinacolato)diboron affords chiral tertiary organoboronate esters with a vicinal phosphonate group in good yields and enantiomeric excess. Linear aliphatic, aromatic, and heteroaromatic substituents at the β-position can be accommodated, and oxidation of the borylated organophosphonate products leads to β-hydroxyphosphonates. 相似文献
10.
This paper describes an efficient enantioselective conjugate addition of highly stable potassium trifluoro(organo)borates to α,β-unsaturated amides. This reaction, catalyzed by chiral rhodium(I) complexes affords Michael adducts with high yields and enantiomeric excesses up to 95%. 相似文献
11.
3-Fluorobutenone (2) reacts under Zn(II) catalysis in ethanol solution with active methylene compounds such as anthrone and aromatic phenols to give products of the addition of one unit of 3-fluorobutenone. 相似文献
12.
13.
Emmanuel Riguet 《Tetrahedron letters》2009,50(29):4283-1707
Novel guanidinyl pyrrolidine salts are useful bifunctional organocatalysts for the asymmetric addition of malonates to enones. These organocatalysts are effective under a wide range of reaction conditions and afford products in high yield and enantioselectivity. 相似文献
14.
Keiji Tanino 《Tetrahedron letters》2006,47(6):861-864
A novel cyclization reaction of a 1,1-dibromoalkene derivative having an α,β-unsaturated ester moiety was developed. Under the influence of Me2CuLi, the 1,1-dibromoalkene was converted into a (Z)-vinylcopper species which in turn underwent an intramolecular conjugate addition reaction with the α,β-unsaturated ester moiety. Five-, six-, and seven-membered carbocycles were constructed by the present method. The substrate having an epoxide moiety also afforded a five-membered product via a 5-exo type intramolecular cyclization reaction. 相似文献
15.
A stereoselective tandem conjugate addition reaction with a chiral amine-derived nucleophile is reported in which the enolate intermediate is quenched with 1,2-dibromotetrachloroethane as a mild brominating reagent. X-ray analysis of a subsequent derivative was used to prove the configuration at each of the four newly formed stereocenters. The resulting α-bromoester underwent selective transesterification catalyzed by mild base to allow selective manipulation of the two ester groups of the product. 相似文献
16.
Valuable chiral N-Boc-β-benzyl-β-amino acid was concisely synthesized via construction of chiral NBoc-3-benzyl-5-oxoisoxazolidine through cross-metathesis/conjugate addition/oxidation.All of the starting materials for the synthesis of chiral N-Boc-β-benzyl-β-amino acid are cheap,and two-step short procedure make it easy for the rapid construction of various chiral β-arylmethyl-β-amino acids and important drugs,such as sitagliptin phosphate. 相似文献
17.
Kazuyuki Sato 《Journal of fluorine chemistry》2003,121(1):105-107
Reaction of ethyl bromodifluoroacetate with a variety of Michael acceptors was tremendously improved by the addition of TMEDA. Using this additive, 1,4-adducts were formed exclusively, and any 1,2-adducts or radical adducts were not obtained. THF or other low boiling solvents can be used as a solvent. This simplifies the work-up of the reaction effectively. 相似文献
18.
Martin Brunner 《Tetrahedron letters》2004,45(15):3063-3065
Highly diastereoselective aldol additions of pure (2R,4S)-2-tert-butyloxazolidinone-3,4-dicarboxylic acid 3-tert-butyl ester 4-methyl ester 1 are reported. While achiral carbonyl compounds lead to mixtures of diastereomers, the double stereodifferentiation of chiral aldehydes gave a single product isomer. The relative and absolute configurations of the aldol products were assigned by NOESY. 相似文献
19.
Newly designed phosphino-phenol 1c was found to be an efficient chiral auxiliary for copper-mediated asymmetric conjugate addition of diethylzinc to acyclic enones. High enantioselectivity up to >99% ee was achieved in the reaction of acyclic α,β-enones. 相似文献
20.
David W. Jeffery 《Tetrahedron letters》2004,45(47):8667-8671
A tandem conjugate addition/cyclisation approach, that allows the synthesis of chiral highly substituted cyclohexanones and cyclohexenones, which is applicable to natural product syntheses has been developed. 相似文献