共查询到20条相似文献,搜索用时 15 毫秒
1.
Herein we describe a novel approach for the synthesis of a chiral 1,2,3-trisubstituted indane, a privileged substructure in medicinal chemistry, via an enantioselective nitroaldol reaction and subsequent intramolecular Michael addition. The asymmetric copper(II)-catalyzed reactions of ortho-formyl cinnamates, ortho-formyl cinnamonitrile, or ortho-formyl α-benzalketones with nitromethane were carried out using the C1-symmetric chiral secondary diamine L1 as a ligand, which afforded the nitroaldol products in high yields (up to 92%) and with good to excellent enantioselectivities (up to 97%) under mild conditions. The notable effect of the base and the dosage of nitromethane on the reaction are also discussed. 相似文献
2.
An effective chiral palladium catalyst [Pd(CH(3)CN)(2)(S)-Tol-BINAP](SbF(6))(2) (2b) is developed for asymmetric glyoxylate-ene reactions. This palladium dicationic catalyst provides a simple but efficient approach to the asymmetric synthesis of alpha-hydroxy esters in excellent yields with high enantioselectivities at relatively higher reaction temperature (60 degrees C). 相似文献
3.
A strategy for exo and enantioselective 1,3-dipolar cycloaddition of azomethine imines to 2-acryloyl-3-pyrazolidinone is described. The corresponding cycloadducts are isolated with high diastereoselectivities (up to >96:4 exo/endo) and enantioselectivities (up to 98% ee). 相似文献
4.
Yu F Zhou JN Zhang XC Sui YZ Wu FF Xie LJ Chan AS Wu J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(50):14234-14240
In the presence of PhSiH(3) as the reductant, the combination of enantiomeric dipyridylphosphane ligands and Cu(OAc)(2)·H(2)O, which is an easy-to-handle and inexpensive copper salt, led to a remarkably practical and versatile chiral catalyst system. The stereoselective formation of a selection of synthetically interesting β-, γ- or δ-halo alcohols bearing high degrees of enantiopurity (up to 99.9% enantiomeric excess (ee)) was realized with a substrate-to-ligand molar ratio (S/L) of up to 10,000. The present protocol also allowed the hydrosilylation of a diverse spectrum of alkyl aryl ketones with excellent enantioselectivities (up to 98% ee) and exceedingly high turn-over rates (up to 50,000 S/L molar ratio in 50 min reaction time) in air, under very mild conditions, which offers great opportunities for the preparation of various physiologically active targets. The synthetic utility of the chiral products obtained was highlighted by the efficient conversion of optically enriched β-halo alcohols into the corresponding styrene oxide, β-amino alcohol, and β-azido alcohol, respectively. 相似文献
5.
1,4-Diaryl-1,3-butadiynes react with cyclic amines, such as pyrrolidine, piperidine, and morpholine in the presence of a catalytic amount of CuCl to afford amino-substituted naphthalene derivatives with good to high yields. The new catalytic procedure provides an atom-economic, one-pot synthetic method for the synthesis of naphthalene derivatives from easily available 1,4-diaryl-1,3-butadiynes. 相似文献
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8.
A highly enantioselective Michael addition of nitro esters to 2-enoyl-pyridine N-oxides was developed by using chiral copper catalysts. The Michael addition products can be obtained in high yields and with up to 96% ee. 相似文献
9.
Axially chiral BINIM-Ni(II) complexes are effective catalysts in the asymmetric 1,3-dipolar cycloaddition reactions of azomethine ylides and N-arylmaleimides to give the corresponding adducts in good yields and up to 95% enantiomeric excesses. 相似文献
10.
González AZ Benitez D Tkatchouk E Goddard WA Toste FD 《Journal of the American Chemical Society》2011,133(14):5500-5507
In this article the utility of phosphoramidite ligands in enantioselective Au(I) catalysis was explored in the development of highly diastereo- and enantioselective Au(I)-catalyzed cycloadditions of allenenes. A Au(I)-catalyzed synthesis of 3,4-disubstituted pyrrolidines and γ-lactams is described. This reaction proceeds through the enantioselective Au(I)-catalyzed cyclization of allenenes to form a carbocationic intermediate that is trapped by an exogenous nucleophile, resulting in the highly diastereoselective construction of three contiguous stereogenic centers. A computational study (DFT) was also performed to gain some insight into the underlying mechanisms of these cycloadditions. The utility of this new methodology was demonstrated through the formal synthesis of (-)-isocynometrine. 相似文献
11.
《Tetrahedron: Asymmetry》2006,17(14):2046-2049
Chiral iminopyridines prepared in a modular fashion from monoterpenic (camphor-derived) ketones and pyridinylalkylamines catalyze the enantioselective Henry (nitro aldol) reaction between nitromethane and o-anisol in the presence of copper(II) acetate, with high yields and good ee (up to 86%) under straightforward experimental conditions without the need for air or moisture exclusion. 相似文献
12.
[Structure: see text] An efficient method for the enantioselective tandem reductive aldol reaction of methyl acrylate with aldehydes is reported. By using a copper(I) precursor and a proper diphosphane ligand, high reactivities can be reached, with TOF up to 40,000 h-1. Taniaphos-based ligands lead to enantioselectivities of up to 97% in the case of the major syn diastereoisomer. 相似文献
13.
Genin E Toullec PY Antoniotti S Brancour C Genêt JP Michelet V 《Journal of the American Chemical Society》2006,128(10):3112-3113
A highly efficient gold-catalyzed cyclization reaction of various functionalized acetylenic acids is described. The cyclizations are conducted in the presence of Au(I) catalyst in acetonitrile at room temperature in a short reaction time. The reaction conditions are compatible with several functional groups, such as ester, alkene, alkyne, chloro, and free or protected alcohol, and lead to original gamma-lactones in good to excellent yields. 相似文献
14.
Takayuki DoiNobuaki Fujimoto Jun WatanabeTakashi Takahashi 《Tetrahedron letters》2003,44(10):2161-2165
We have developed a practical route for the synthesis of peptides containing unnatural amino acids. Mizoroki-Heck reaction of polymer-supported dehydroalanine, followed by asymmetric hydrogenation was accomplished using Pd(0) and Rh(I)-DuPHOS catalysts, respectively, leading to 36 dipeptides containing phenylalanine derivatives with high stereocontrol. 相似文献
15.
《Tetrahedron: Asymmetry》2007,18(11):1376-1382
Chiral phosphine-salen type ligand L4 prepared from (R)-2-(diphenylphosphino)-1,1′-binaphthyl-2′-amine was found to be a fairly effective chiral ligand for Cu(I)-promoted enantioselective Henry reactions of arylaldehydes with nitromethane to give the corresponding adducts in moderate enantioselectivities and moderate to good yields. 相似文献
16.
An easy synthesis of (Z)-1-alkylidene-1,3-dihydroisobenzofurans and 1H-isochromenes by palladium-catalyzed cycloisomerization of readily available 2-alkynylbenzyl alcohols under neutral conditions is reported. Reactions were carried out at 70-100°C in the presence of catalytic amounts (1-2%) of PdI2 in conjunction with 2 equiv. of KI for 1.5-24 h. The preference towards the 5-exo-dig cyclization mode (leading to 1,3-dihydroisobenzofurans) or the 6-endo-dig cyclization mode (leading to isochromenes) turned out to be dependent on the substitution pattern of the substrate as well as reaction conditions. In several cases, by properly adjusting the reaction conditions, the same substrate could be selectively converted into either the dihydroisobenzofuran or the 1H-isochromene derivative. 相似文献
17.
[formula: see text] A divalent palladium-catalyzed coupling reaction of electron-deficient alkynes and acrolein or MVK (methyl vinyl ketone) was developed. The reaction provides an efficient method to synthesize gamma,delta-unsaturated carbonyls. A mechanism involving acetoxypalladation of alkyne, followed by insertion of alkene and protonolysis of the C-Pd bond, is proposed. The protonolysis of the carbon-palladium bond with the assistance of bidentate nitrogen containing ligands is the key step in this tandem reaction. 相似文献
18.
[reaction: see text] The catalytic, enantioselective [3 + 2] cycloaddition reaction of 1-alkyl-substituted allenylsilanes with alpha-imino ester has been achieved by means of [Cu(MeCN)(4)]BF(4)/(R)-DM-SEGPHOS catalyst to afford silyl-substituted dehydroproline derivatives in high yields and enantioselectivities. 相似文献
19.
Daqian Xu Qiangsheng Sun Zhengjun Quan Wei Sun Xicun Wang 《Tetrahedron: Asymmetry》2017,28(7):954-963
A series of chiral tridentate ligands derived from readily available enantiopure l-proline were designed and synthesized. The ligands together with Cu(OAc)2 were successfully used in asymmetric Henry reactions. Various structurally divergent aldehydes and nitromethane were converted into versatile β-nitro alcohols in MeOH at room temperature with very good yields (up to 85%) and enantioselectivities (up to 86%). 相似文献
20.
《Tetrahedron: Asymmetry》2000,11(13):2765-2779
The ligands 6-[(diphenylphosphanyl)methoxy]-4,8-di-tert-butyl-2,10-dimethoxy-5,7-dioxa-6-phosphadibenzo[a,c]cycloheptene, 1, (S)-4-[(diphenylphosphanyl)methoxy]-3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4a′]dinaphthalene, (S)-2, and (S)-4-[(diphenylphosphanyl)methoxy]-2,6-bis-trimethylsilanyl-3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalene, (S)-3, (S)-2-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yloxymethyl)pyridine, (S)-4, and (S)-2-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yloxy)pyridine, (S)-5, have been easily prepared.The cationic complexes [Pd(η3-C3H5)(L-L′)]CF3SO3 (L–L′=1–(S)-5) and [Pd(η3-PhCHCHCHPh)(L–L′)]CF3SO3 (L–L′=(S)-2–(S)-4) were synthesized by conventional methods starting from the complexes [Pd(η3-C3H5)Cl]2 and [Pd(η3-PhCHCHCHPh)Cl]2, respectively. The behavior in solution of all the π-allyl- and π-phenylallyl-(L–L′)palladium derivatives 6–14 was studied by 1H, 31P{1H}, 13C{1H} NMR and 2D-NOESY spectroscopy. As concerns the ligands (S)-4 and (S)-5, a satisfactory analysis of the structures in solution was possible only for palladium–allyl complexes [Pd(η3-C3H5)((S)-4)]CF3SO3, 11, and [Pd(η3-C3H5)((S)-5)]CF3SO3, 12, since the corresponding species [Pd(η3-PhCHCHCHPh)((S)-4)]CF3SO3, 13, and [Pd(η3-PhCHCHCHPh)((S)-5)]CF3SO3, 14, revealed low stability in solution for a long time. The new ligands (S)-2–(S)-5 were tested in the palladium-catalyzed enantioselective substitution of (1,3-diphenyl-1,2-propenyl)acetate by dimethylmalonate. The precatalyst [Pd(η3-C3H5)((S)-2)]CF3SO3 afforded the allyl substituted product in good yield (95%) and acceptable enantioselectivities (71% e.e. in the S form). A similar result was achieved with the precatalyst [Pd(η3-C3H5)((S)-3)]CF3SO3. The nucleophilic attack of the malonate occurred preferentially at allylic carbon far from the binaphthalene moiety, namely trans to the phosphite group. When the complexes containing ligands (S)-4 and (S)-5 were used as precatalysts, the product was obtained as a racemic mixture in high yield. The number of the configurational isomers of the Pd-allyl intermediates present in solution in the allylic alkylation and the relative concentrations are considered a determining factor for the enantioselectivity of the process. 相似文献