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1.
Enantioselective Friedel-Crafts alkylation reactions of a series of substituted indoles with methyl trifluoropyruvate, catalyzed by a chiral nonracemic C(2)-symmetric 2,2'-bipyridyl copper(II) triflate complex, are described. The corresponding 3,3,3-trifluoro-2-hydroxy-2-indole-3-yl-propionic acid methyl esters were formed in good yield and in high enantiomeric excess (up to 90%). This is the first report of the use of a chiral nonracemic 2,2'-bipyridyl ligand in catalytic and enantioselective Friedel-Crafts alkylation reactions. The structural characterization of a copper(II) chloride complex of the chiral 2,2'-bipyridyl ligand by X-ray crystallography is also presented. [reaction: see text] 相似文献
2.
The evaluation of a chiral, nonracemic and C2-symmetric 2,2'-bipyridyl ligand in copper(I)-catalyzed asymmetric allylic oxidation reactions of a series of cyclic alkenes with tert-butyl peroxybenzoate is reported (up to 91% ee, the highest reported enantioselectivity for a bipyridyl ligand copper(I) complex to date). 相似文献
3.
An efficient synthesis of a low molecular weight, chiral nonracemic and C(2)-symmetric bipyridyl ligand is reported. The ligand was prepared using a catalytic asymmetric dihydroxylation reaction of a pyrindine as a key step. The ligand was evaluated in the asymmetric copper(I)-catalyzed cyclopropanation reactions of a series of alkenes and diazoesters. Very high diastereoselectivities and enantioselectivities were observed (>95:5 dr and up to 99% ee). These are the highest reported stereoselectivities for a chiral bipyridyl ligand. [structure: see text] 相似文献
4.
Guillemot G Neuburger M Pfaltz A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(32):8960-8970
A synthetic route to tetradentate chiral N(4) ligands has been developed with the aim to study the potential of corresponding iron and manganese complexes as catalysts for enantioselective epoxidation. These ligands, which contain two oxazoline rings and two trialkylamino groups as coordinating units, are readily prepared in enantiomerically pure form by the reaction of chiral 2-chloromethyloxazolines with achiral N,N'-dimethylethane-1,2-diamine or chiral (R,R)-N,N'-dimethylcyclohexane-1,2-diamine. The ligands derived from N,N'-dimethylethane-1,2-diamine reacted with anhydrous metal halides MnCl(2) and FeCl(2) in a stereoselective manner to give octahedral mononuclear complexes that have the general formula Delta-[(L)MCl(2)]. In contrast, the ligands derived from N,N'-dimethylcyclohexane-1,2-diamine formed complexes with different coordination modes depending on the diastereomer employed: in one case the metal ion was found to be pentacoordinate, in the other case a hexacoordinated complex was observed. The structure of a series of Fe and Mn complexes was determined by X-ray analysis. The coordination chemistry of these ligands was further studied by X-ray and NMR analyses of the diamagnetic isostructural complexes [(L)ZnCl(2)]. Analogous ionic complexes, which were prepared by removing chloride with silver trifluoromethanesulfonate or hexafluoroantimonate, were tested as catalysts for the epoxidation of olefins. 相似文献
5.
Bacchi Alessia Pelizzi Giancarlo Minardi Giovannina Pistuddi Angelo M. Solinas Costantino Chelucci Giorgio 《Transition Metal Chemistry》2002,27(3):274-278
Metal complexes of general formula M(L)X2 and M(L)X3 [L = (4S,5S)-2,2-dimethyl-4,5-bis{6-[(4,5-dihydro-4-(S)-(1-methylethyl)oxazol-2-yl)pyridin-2-yl]}-1,3-dioxolane] were obtained by reacting, respectively, CoII, CuII, NiII, and ZnII nitrate salts and the RhIII chloride salt, with a chiral C2-symmetric bis(oxazolinylpyridinyl)dioxolane (L) ligand, in MeOH/CHCl3 solution. A single crystal X-ray analysis was carried out on [Ni(L)(OH2)2](NO3)2 · 2H2O and the molecular structure of L was also determined. In the free ligand the two symmetric arms are essentially planar and oriented nearly perpendicular to the dioxolane average plane. In the Ni complex one seven-membered and two five-membered chelation rings are formed. The metal atom also lies on the C2 axis, and two symmetry-related water molecules complete the octahedral coordination environment. Both compounds crystallize in chiral space groups; the ligand crystallizes in orthorhombic system, space group C 2 2 21, Z = 4; the nickel complex crystallizes in tetragonal system, space group P 43 21 2, Z = 4. 相似文献
6.
Two novel C 2-symmetric bis-oxazoline ligands were synthesized and their complexes with Cu(OAc)2 were studied as catalysts in the enantioselective Henry reaction of 4-nitrobenz-aldehyde with nitromethane giving high yield of nitro aldol with ee up to 40%. 相似文献
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8.
Al Majid AM Islam MS Al-Othman ZA Al-Salhoob AF Barakat A 《Molecules (Basel, Switzerland)》2012,17(5):5550-5563
The hemilabile chiral C2 symmetrical bidentate substituted amide ligands (1R,2R)-5(a-d) and (1S,2S)-6(a-d) were synthesized in quantitative yield from (1R,2R)-(+)-3-methylenecyclo-propane-1,2-dicarboxylic acid (1R,2R)-3 and (1S,2S)-(-)-3-methylene-cyclopropane-1,2-dicarboxylic acid (1S,2S)-3, in two steps, respectively. The chiral Feist's acids (1R,2R)-3 and (1S,2S)-3 were obtained in good isomeric purity by resolution of trans-(±)-3-methylene-cyclopropane-1,2-dicarboxylic acid from an 8:2 mixture of tert-butanol and water, using (R)-(+)-α-methylbenzyl amine as a chiral reagent. This process is reproducible on a large scale. All these new synthesized chiral ligands were characterized by 1H-NMR, 13C-NMR, IR, and mass spectrometry, as well as elemental analysis and their specific rotations were measured. These new classes of C2 symmetric chiral bisamide ligands could be of special interest in asymmetric transformations. 相似文献
9.
《Tetrahedron: Asymmetry》2006,17(13):1901-1929
Synthetic procedures for a large variety of C2-symmetric chiral diols are reviewed. Prominent among these procedures are enantioselective reductions, epoxide-cleavages, dihydroxylation of olefins, and synthetic transformations. Applications of these diols as chiral auxiliaries/ligands for several important reactions are also highlighted. 相似文献
10.
A new method for generating group 3 metal complexes containing radical-anionic 2,2'-bipyridyl (bipy) ligands is described that relies on hydrogen-atom abstraction from dearomatized biheterocyclic complexes. This method does not involve electron transfer to neutral 2,2'-bipyridyl or salt metathesis between the lithium salt of the 2,2'-bipyridyl radical anion and group 3 metal halides. The new metal complexes were characterized by single-crystal X-ray diffraction, electron paramagnetic resonance, and absorption spectroscopy. Density functional theory (DFT) calculations were used to probe the electronic structure of these compounds. All these methods support the radical-anionic character of bipy in all bipy compounds presented. 相似文献
11.
《Tetrahedron: Asymmetry》2001,12(20):2851-2859
New chiral ligands, including bi- and tridentate thiazoline derivatives, analogues of known oxazolines, have been synthesized by a general and convenient procedure, starting from dithioesters and commercial enantiopure 2-aminoalcohols. A preliminary test shows the ability of such ligands to act as asymmetric catalysts in Pd-catalyzed allylic substitution reaction. 相似文献
12.
Novel C(2)-symmetric diphosphine ligands possessing only the planar chirality of ruthenocene, 1,1'-bis(diphenylphosphino)-2,2'-disubstituted-ruthenocenes (4), were prepared. With this kind of ligands, excellent enantioselectivity and especially highly catalytic activity in palladium-catalyzed asymmetric allylic substitutions of rac-1,3-diphenyl-2-propenyl acetate (9) were observed, compared to their ferrocene analogues 1. Good enantioselectivity and highly catalytic activity were also obtained with 4 in palladium-catalyzed asymmetric allylic substitutions of cyclohexen-1-yl acetate (12). Further study on the effect of R in ester group on enantioselectivity of 4 showed an opposite trend compared with their ferrocene analogues 1 in asymmetric allylic substitutions. For ruthenocene ligands 4, the one with the smaller R in the ester group gave higher enantioselectivity for the palladium-catalyzed asymmetric allylic substitutions of 9, while a converse trend had been observed with 1. However, for the palladium-catalyzed asymmetric allylic substitutions of 12, ligand 4 with a larger R in the ester group resulted in somewhat higher enantioselectivity but still an opposite trend with ligand 1. The X-ray diffraction study of crystal structures of 4 and 1 with Pd(II) was carried out and showed that the enantioselectivity was correlated to the twist angle existing in the palladium complex. 相似文献
13.
《Tetrahedron: Asymmetry》2014,25(4):327-333
First synthesis of C2-symmetric chiral O,N,N,O-tetradentate 2,2-bipyridyldiolpropane ligands is described. The Mukaiyama–Michael reaction was applied as an important reaction for the synthesis of 2,2-bipyridylpropane 9. Among the ligands synthesized, ligand 11 exhibits excellent chiral induction (up to 97% ee) in diethylzinc addition to various aldehydes. The use of additional Lewis acid such as Ti(OiPr)4 in diethylzinc addition reaction is not required for the present catalytic system. 相似文献
14.
15.
A chiral and fluorescent columnar mesogen prepared from chiral binaphthols is reported. This liquid crystal comprises a C2-symmetric chiral core with two staggered aromatic planes. Its hexagonal columnar (Col(h)) mesophase was characterized by appropriate physical methods. 相似文献
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17.
Malkov AV Pernazza D Bell M Bella M Massa A Teplý F Meghani P Kocovský P 《The Journal of organic chemistry》2003,68(12):4727-4742
A series of modular bipyridine-type ligands 1 and 3-9 has been synthesized via a de novo construction of the pyridine nucleus. The chiral moieties of these ligands originate from the isoprenoid chiral pool, namely, beta-pinene (10 --> 1), 3-carene (14 --> 3 and 5), 2-carene (28 --> 4), alpha-pinene (43 --> 6-8), and dehydropregnenolone acetate (48 --> 9), respectively. Copper(I) complexes, derived from these ligands and (TfO)(2)Cu (1 mol %) upon an in situ reduction with phenylhydrazine, exhibit good enantioselectivity (up to 82% ee) and unusually high reaction rate (typicaly 30 min at room temperature) in allylic oxidation of cyclic olefins (52 --> 53). Copper-catalyzed cyclopropanation proceeded with < or =76% enantioselectivity and approximately 3:1 to 99:1 trans/cis-diastereoselectivity (54 --> 55 + 56). The level of the asymmetric induction is discussed in terms of the ligand architecture that controls the stereochemical environment of the coordinated metal. 相似文献
18.
Carbohydrates are increasingly used as starting materials for the synthesis of enantiopure ligands. They contain a considerable number of stereocenters, and compounds with all possible configurational combinations are readily available. This tutorial review focuses on ligands obtained by the introduction of phosphorus functionalities (mainly phosphinite, phosphite or phosphine) into a carbohydrate framework. They are classified according to their structural features. In this review, ligands are organised as C1 ligands with a pyranoside or furanoside structure, and C2 ligands. Particular attention is paid to water soluble ligands prepared from carbohydrates. General methods for the preparation of the ligands are presented in order to show how the backbones can be obtained from simple carbohydrates. The catalytic results obtained in commonly studied processes are presented in tables in order to facilitate the comparison between the ligands. The advantages and limitations of the use of ligands based on carbohydrates are discussed. 相似文献
19.
A series of new C2-symmetric chiral aza crown ether macrocycles 1–4 have been synthesized from (S)-3-aryloxy-1,2-propanediol and (S)-1,2-propanediol for the enantiomeric recognition of amino acid ester derivatives. These new macrocycles have been shown to be strong complexing agents for primary organic ammonium salts (with K up to 176.93 M?1 and ΔG° up to 12.81 kJ mol?1) by 1H NMR titration. These macrocyclic host exhibited enantioselective bonding toward the d-enantiomer of phenylalanine methyl ester hydrochloride with KD/KL up to 6.87 in CDCl3 with 0.25% CD3OD. 相似文献
20.
The chiral bisamidine 5 has been prepared in just two steps from malonodinitrile. In the monocationic form this compound adopts a planar conformation with an almost convergent orientation of two N-H groups. Ketones, aldehydes, and nitro compounds are assumed to bind to this strongly polar cleft via hydrogen bonds, resulting in a Lewis-acid-like activation of the carbonyl groups. A broad scope of reactions (Diels-Alder, hetero-Diels-Alder, Friedel-Crafts) can be catalyzed. The observed accelerations surpass the rate effects of neutral hydrogen-bond donors such as thioureas or TADDOLs. 相似文献