共查询到20条相似文献,搜索用时 15 毫秒
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《Tetrahedron: Asymmetry》2000,11(20):4153-4162
A series of novel chiral aminophosphine ligands with a 5,5,6,6′,7,7′,8,8′-octahydro-1,1′-binaphthyl backbone (H8-MAPs) have been synthesized. The application of these ligands in asymmetric allylic substitutions was examined and higher enantioselectivity was observed than that by using the parent ligand (MAP). Under the optimized conditions, the allylation product can be obtained in up to 90.9% ee with H8-MAP having 3,5-xylyls as chiral inducer. The dramatic effect of the binaphthyl backbone on the enantioselectivity of the reaction can be attributed to the change of the bite angle in H8-MAPs/Pd complexes. 相似文献
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Chiral cationic palladium[bond]phosphinooxathiane complexes have been found to be effective catalysts for enantioselective Diels-Alder (DA) reaction of cyclopentadiene with acyl-1,3-oxazolidin-2-ones to give the corresponding DA adducts in good yield and high enantioselectivity up to 93% ee. 相似文献
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This paper describes the development of a type of novel P-olefin hybrid ligand by the incorporation of terminal olefins onto phosphorus amidite ligands for palladium-catalyzed asymmetric allylic alkylations of indoles and substitutions with amines to give the desired products in 70-97% yield with 91-98% ee. 相似文献
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Okuyama Y Nakano H Takahashi K Hongo H Kabuto C 《Chemical communications (Cambridge, England)》2003,(4):524-525
Easily prepared, chiral sulfideoxathiane ligands are described which give excellent enantioselectivity (up to 99% ee) in the Pd-catalyzed allylic alkylation of 1,3-diphenyl-2-propenyl acetate with a range of alkyl malonate nucleophiles. 相似文献
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Several new polymer-supported monophosphite ligands have been developed and the rhodium complexes were shown to be highly efficient, highly enantioselective and easily separable catalysts for asymmetric hydrogenation of itaconates, enamides, α-dehydroamino acid derivatives and β-dehydroamino acid derivatives. 相似文献
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《Tetrahedron: Asymmetry》1998,9(19):3371-3380
Novel chiral P,N-ferrocene ligands, 1-diphenylphosphino-1′-oxazolinylferrocenes, were prepared from ferrocene via 1,1′-bis(tributylstannyl)ferrocene and 1-diphenylphosphino-1′-methoxycarbonylferrocene as intermediates, and with this new kind of ligand up to 91% ee with 99% chemical yield was afforded for the palladium-catalyzed allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethylmalonate anion. The complexation behavior of this kind of ligand with dichlorobis(acetonitrile)palladium and bis(μ-chloro)(1,3-diphenyl-η3-allyl)dipalladium was investigated. 相似文献
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《Tetrahedron: Asymmetry》2000,11(5):1193-1198
Pyrrolidinyl- 2 and 2-azanorbornylphosphinooxazolidines 3, a new type of optically active ligands, were synthesized easily and their abilities as ligands were examined in Pd-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate. Enantiomeric excesses of up to 96% have been obtained using 1 mol% of [PdCl(η3-C3H5)]2 and 2.1 mol% of 2. 相似文献
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Konstantin N. Gavrilov Sergey V. ZheglovMariya N. Gavrilova Ilya V. ChuchelkinNikolay N. Groshkin Eugenie A. RastorguevVadim A. Davankov 《Tetrahedron letters》2011,52(43):5706-5710
A small family of readily available phosphoramidite ligands, including compounds with P∗-stereocenters, has been prepared from phenyl-substituted 1,2-diols as simple and cheap starting materials. Using these ligands, up to 84% ee was achieved in Pd-catalyzed asymmetric allylic substitution. The influence of structural modules such as asymmetric atoms and steric demand on the enantioselectivity is discussed. 相似文献
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Elżbieta Wojaczyńska Mariola Zielińska-Błajet Ilona Turowska-Tyrk Jacek Skarżewski 《Tetrahedron: Asymmetry》2010,21(7):853-858
Phenyl sulfides derived from Cinchona alkaloids, 9-PhS-epi-CD, 9-PhS-epi-QN, 9-PhS-epi-QD, and 9-PhS-QN were oxidized into the corresponding sulfoxides. Regardless of the oxidation system used (NaIO4, TEMPO/NaOCl, VO(acac)2/chiral Schiff base/H2O2) a similar stereochemical outcome of the oxidation was observed. Four pure epimers of sulfoxides 9-PhSO-epi-CD and 9-PhSO-epi-QN were isolated and fully characterized (X-ray, CD, 1H NMR-pattern). The chiral sulfoxides as well as the corresponding sulfides and sulfones were tested in the Pd-catalyzed allylic alkylation of dimethyl malonate with rac-1,3-diphenyl-2-propenyl acetate. The sulfoxides obtained from Cinchona alkaloids bearing the additional stereogenic center gave the main product of configuration dependent on the chirality of alkaloid framework only. Similar ees (up to 60%) but significantly higher yields (90%) were obtained as compared to the reaction with the corresponding thioethers. The results were in agreement with nucleophilic attack directed at the allylic carbon located trans to the sulfur atom in the M-shaped intermediate η3-allylpalladium complex. 相似文献
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《Tetrahedron: Asymmetry》2005,16(15):2551-2557
Easily prepared, chiral sulfideoxathiane ligands are described, which give excellent enantioselectivities (up to 99% ee) in the Pd-catalyzed allylic alkylation of 1,3-diphenyl-2-propenyl acetate with a range of alkyl malonate nucleophiles. 相似文献
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[reaction: see text] Polymer-supported bisBINOL ligands were successfully utilized for the immobilization of multicomponent asymmetric catalysts. The polymer-supported Al-Li-bis(binaphthoxide) (ALB) catalyst was more effective than the dendrimer-supported ALB in the Michael reaction of 2-cyclohexen-1-one with dibenzyl malonate affording the adduct in 91% yield with 96% ee. The polymer was also effective for the immobilization of a mu-oxodititanium complex that promoted carbonyl-ene reaction of ethyl glyoxalate with alpha-methyl styrene to provide the adduct with up to 98% ee. 相似文献
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Fang Xie 《Tetrahedron letters》2008,49(6):1012-1015
The novel C2-symmetric metallocene-based ligands with only planar chirality were synthesized easily and applied in palladium-catalyzed asymmetric allylic substitution with excellent enantioselectivity and high catalytic activity. When two ester groups on Cp rings of the metallocene were replaced by hydroxymethyl groups, opposite configuration of the product was obtained with high catalytic activity and excellent enantioselectivity. The opposite configuration of products was also obtained when the hydroxyl groups were protected as esters or ethers. These results might be attributed to the different configuration of the diphosphine ligands-Pd(II) complexes. 相似文献
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Eleven novel aminophosphine ligands have been synthesized, all of which contain a chiral 2,2' '-bridged biferroceno unit as part of a biferrocenoazepine substructure. The efficiency of these compounds as chiral auxiliaries in palladium-mediated allylic substitution reactions has been investigated. Depending on the degree of (steric) fit between proper ligands and cyclic or noncyclic substrates, reactions with 46-87% ee were achieved. The molecular structure of a palladium dichloride complex of one of the ligands was determined by X-ray diffraction and compared to its binaphthyl analogue. In the solid state, the azepine substructure of these two complexes adopts totally different conformations with either local C(2) (binaphthyl) or local C(1) (biferrocene derivative) symmetry. These structural changes are well-reproduced by empirical force field calculations and are also reflected in significantly different behavior in asymmetric catalysis. 相似文献
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A series of phosphines based on disaccharides containing a d-glucosamine framework were prepared and tested for their abilities as ligands for the palladium(0)-catalyzed asymmetric allylic allylation of racemic 1,3-diphenyl-2-propenyl acetate with various nucleophiles. In contrast to previous results exploiting monosaccharides, the iminophosphines generally afforded higher enantiomeric excesses, up to 99%. 相似文献
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《Tetrahedron: Asymmetry》2000,11(19):4027-4036
New chiral quinolylmethyloxazolines and acridininyloxazolines were prepared and assessed in the enantioselective palladium-catalyzed allylic substitution of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate. The introduction of a benzo-fused substituent on the pyridine ring not containing the chiral backbone resulted in the switch of the expected chiral sense of enantioselection of the reaction. Enantiomeric excesses up to 78% were obtained. 相似文献
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Robé E Perlikowska W Lemoine C Diab L Vincendeau S Mikolajczyk M Daran JC Gouygou M 《Dalton transactions (Cambridge, England : 2003)》2008,(21):2894-2898
Diphosphine sulfides derived from 2,2'-biphosphole have been efficiently synthesized in an enantiomerically pure form by a four step synthetic sequence. These S,S-ligands were used for the first time in Pd-catalyzed asymmetric allylic alkylation. Good yields and enantiomeric excess up to 73% were obtained. 相似文献
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《Tetrahedron: Asymmetry》1998,9(22):4009-4020
New enantiomerically pure 1,4-diols and 1,4-aminoalcohols have efficiently been prepared in one and two steps, respectively, from a commercially available camphor derived exo fused lactone. Using sterically hindered amines, an aldol addition of two lactone molecules was observed and the stereochemistry of the products was determined by X-ray crystallography. 相似文献