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1.
Palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate (4) with a dimethyl malonate-BSA-LiOAc system has been successfully carried out in the presence of chiral phosphine-hydrazone ligands such as 3a in good yields with good enantioselectivities (up to 84% ee). 相似文献
2.
Hanna K. Cotton 《Tetrahedron》2006,62(24):5632-5640
Screening of metallocenethiolate ligands for copper(I)-catalyzed substitution of allylic acetates with Grignard reagents has been carried out. The previously used ligand, lithium (R,Sp)-2-(1-dimethylaminoethyl)ferrocenylthiolate (4a), possessing both central and planar chirality, was the starting point for the screening. It was found that the diastereomeric ligand lithium (R,Rp)-2-(1-dimethylaminoethyl)ferrocenylthiolate (4b) exhibiting reversed planar chirality gave increased enantioselectivity in the allylic substitution, at least when cinnamyl acetate was used as a substrate. The ruthenocene-based ligand lithium (R,Sp)-2-(1-dimethylaminoethyl)ruthenocenylthiolate (4c) gave an enhanced reaction rate, but lower chiral induction. The use of disulfide bis[(R,Sp)-2-(1-dimethylaminoethyl)ferrocenyl]disulfide (7a) as a ligand precursor worked well but resulted in lower enantioselectivity. 相似文献
3.
Nuno Mateus 《Journal of organometallic chemistry》2006,691(10):2297-2310
A new method to synthesize both enantiomers of 2-diphenylphosphino-ferrocenecarboxaldehyde with the phosphine group protected as a thiophosphine group was developed. These aldehydes react with 1,2 or 1,3 diols to give, in good yields, new chiral phosphine-acetals. For unsymmetrical (R)-1,3-butanediol, the new asymmetrical acetalic carbon is asymmetric and its configuration was completely controlled by the chirality of the diol. These new P,O ligands were tested in the palladium-catalyzed asymmetric allylic substitution of 1,3-diphenylprop-2-enylacetate. Good yields and enantioselectivities up to 77% were observed. The catalytic performances of two diastereoisomeric ligands with opposite configurations in planar chirality only proved to be significantly different, showing a strong influence of both planar and central chiralities. 相似文献
4.
A series of thiazoline ligands, analogues of well-known oxazolines, easily prepared from chiral aminoalcohols and appropriate dithioesters, was tested in the Pd-catalysed allylic substitution. A systematic comparison with the corresponding oxazolines (using literature data or our own tests) has been made for each case. Some important differences (between their catalytic activity and enantioselectivity) were noted for the two types of ligands, especially in the case of bis(thiazolines) and bis(oxazolines). 相似文献
5.
LTMP (5 equiv) metalates randomly veratric acid (1). Under external quench conditions, the thermodynamically more stable lithium 2-lithio-3,4-dimethoxybenzoate (2) reacts with a variety of electrophiles to give versatile building units that are not easily accessible by conventional means. Under in situ quench conditions (LTMP/TMSCl), a reversal of regioselectivity is observed and 6-trimethylsilyl-3,4-dimethoxybenzoic acid (10) is formed predominantly. 相似文献
6.
Indolines bearing different N-protecting groups (N-Tbf and N-Boc) were deprotonated regioselectively at C-2 (sp3 hybridized ortho-H) and C-7 (sp2 hybridized para-H) of the indoline ring, respectively. The generated organolithium intermediates reacted with aldimines to give the desired products in good yields with excellent anti-diastereoselectivities (>99:1). The produced N-Ts-(1-Tbf-indolin-2-yl)methanamine was facilely transformed to a fused heterocyclic compound. 相似文献
7.
A straightforward, high-yielding route to racemic 2-substituted ferrocenecarboxaldehydes has been developed. The synthesis involves the ortho-lithiation/electrophilic quenching of readily accessible 2-ferrocenyl-4,4-dimethyloxazoline (2c), followed by N-methylation, sodium borohydride-mediated reduction, and acidic hydrolysis. 相似文献
8.
We wished to prepare planar chiral compounds by the lithiation of acetal 2-ferrocenyl-(4S,5S)-bis(methoxymethyl)-1,3-dioxolane (1) with butyllithium followed by the reaction with an electrophile. However, the desired products were not observed and two unexpected products, 1-ferrocenyl-1-pentanol (4) of the nucleophilic attack product and 2-ferrocenyl-4,5-dimethylene-1,3-dioxolane (5) of the proton abstraction product, were isolated. Because the nucleophilic attack on acetal carbon is rarely reported so far and both products 4 and 5 may have some potential uses in organic synthesis, these unexpected reactions are investigated in detail. The mechanisms of these reactions are discussed. 相似文献
9.
作为含氮手性配体研究的一部分[1],最近我们报道了手性含氮双齿配体2(结构如Scheme 1所示)的设计合成及其在铜催化下的不对称环丙烷化反应中的应用[2]. 相似文献
10.
Two new vic-dioxime ligands bearing an important redox-active substituent, anti-β-ferrocenylethylaminoglyoxime (1a) and anti-β-ferrocenylethylaminophenylglyoxime (1b), have been synthesized, and their Ni(II), Cu(II) and Co(II) (2a-4a, 2b-4b) complexes were obtained. The composition and structure of the products were determined by elemental analysis, Fourier transform infrared (FT-IR), ultraviolet-visible (UV-vis), mass spectrometry (MS), one-dimensional (1D) 1H, 13C NMR, and two-dimensional (2D) heteronuclear multiple bond correlation (HMBC) techniques. The redox behaviors of the ligands and their complexes were investigated by cyclic voltammetry (CV), which revealed that all the ferrocenyl redox centers are electrochemically independent and undergo a quasi-reversible oxidation at similar potentials. Also, antibacterial activity was studied against Staphylococcus aureus ATCC 29213, Streptococcus mutans RSHM 676, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853. The antimicrobial test results indicated that all the compounds have mild levels of antibacterial activity against both gram negative and gram-positive bacterial species. 相似文献
11.
Based on an ortho-lithiation protocol of 2,2′-dibromo-1,1′-binaphthyl four tetrasubstituted binaphthyls, 2,2′-dibromo-3,3′-diiodo-, 3,3′-dibromo-2,2′-diiodo-, 2,2′,3,3′-tetrabromo-, and 2,2′,3,3′-tetraiodo-1,1′-binaphthyls have been prepared in excellent yield which in turn proved to be versatile key intermediates in the synthesis of various 2,2′,3,3′-tetrasubstituted 1,1′-binaphthyl derivatives. 相似文献
12.
The reaction of allylic compounds with alkyl Grignard reagents in the presence of a catalytic amount of copper N-heterocyclic carbene (NHC) complexes proceeded predominantly in an SN2′ reaction pathway to give γ-substituted product in excellent yield. The method was applied to asymmetric reaction by using optically active NHC ligands. 相似文献
13.
Petr Štěpni?ka Martin Krupa Martin Lama? Ivana Císa?ová 《Journal of organometallic chemistry》2009,694(18):2987-738
Amide coupling between [2-(diphenylphosphino)phenyl]methylamine and 1′-(diphenylphosphino)ferrocene-1-carboxylic acid (Hdpf) afforded a novel diphosphine-amide, 1-{N-[(2-(diphenylphosphino)phenyl)methyl]carbamoyl}-1′-(diphenylphosphino)ferrocene (1), which was subsequently studied as a ligand for palladium(II) complexes. Depending on the metal precursor, the following complexes were isolated: [PdCl2(1-κ2P,P′)] (2), [PdCl(Me)(1-κ2P,P′)] (3), [(μ-1){PdCl2(PBu3)}2] (4) and [(μ-1){PdCl(LNC)}2] (LNC = 2-[(dimethylamino-κN)methyl]phenyl-κC1), featuring this ligand either as a trans-chelating or as a P,P′-bridging donor. The crystal structure of 2·1.25CH2Cl2 was established by X-ray crystallography, corroborating that 1 coordinates as a trans-spanning diphosphine without any significant distortion to the coordination sphere. Complex 2 together with a catalyst prepared in situ from 1 and palladium(II) acetate were tested in Suzuki-Miyaura reaction of aryl bromides with phenylboronic acid in dioxane. 相似文献
14.
Shahla Yekta 《Journal of fluorine chemistry》2004,125(4):517-525
New partially fluorinated binaphthols were obtained using a copper-catalyzed oxidative coupling. The corresponding enantiomerically pure compounds were prepared by fractional crystallization of the corresponding bis(menthyl)carbamates. Nucleophilic aromatic substitution using oxygen- and carbon-based nucleophiles resulted in functionalized derivatives without concomitant racemization. The titanium(IV) complexes of these ligands are catalytically active in the asymmetric oxidation of sulfides. 相似文献
15.
Kosuke Takeuchi 《Tetrahedron》2007,63(45):11101-11107
A radical cascade involving 6-endo cyclization of aryl radicals generated from N-acryloyl-N-(1-methylethenyl)-9-bromophenanthren-10-ylmethylamines, followed by 5-endo-trig cyclization of the resulting α-amidoyl radicals afforded phenanthroindolizidines bearing a methyl substituent at the angular C13a position. 2,3,6-Trimethoxy derivative was synthesized by using this method, but its spectral data were not in accord with those of literature values reported for hypoestestatin 1. Further synthetic study toward hypoestestatin 1 is demonstrated. 相似文献
16.
Xiao-Guang Li Xu Cheng Jun-An Ma Qi-Lin Zhou 《Journal of organometallic chemistry》2001,640(1-2):65-71
New chiral 2-alkyl-8-quinolinyl-oxazolines were synthesized from 2-alkyl-8-quinolinecarboxylic acids and enantiomerically pure amino alcohols using a convenient procedure. Enantioselective palladium-catalyzed allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate in the presence of 2-alkyl-8-quinolinyl-oxazolines provided an alkylation product with an opposite configuration compared to those obtained from unsubstituted quinolinyl-oxazoline ligands. 相似文献
17.
The preparation and properties of mono- versus bis(carbene) Pd(II) complexes bearing unsymmetrical cyano- and ester-functionalized NHC ligands as potential IR probes were studied in detail. Direct reaction of Pd(OAc)2 with functionalized imidazolium salts afforded either bis(carbene) (3a, c) or monocarbene complexes (5, 6) with a N-coordinated imidazole co-ligand. The latter were exclusively obtained with N-ethylene substituted salts, which were found to undergo N-C cleavage reaction. The milder Ag-carbene transfer reaction on the other hand was tolerable to the length of the substituents and the nature of the functional groups. All bis(carbene) complexes (3a-c, 4a-c) were obtained as a inseparable mixture of square-planar trans-anti and trans-syn rotamers. The identity, ratio and dynamic equilibrium of these rotamers have been investigated and the relatively high rotational barrier for rotamers of 3a was estimated to be about 74 kJ mol−1 at 380 K. All eight complexes were fully characterized by NMR and IR spectroscopies, ESI mass spectrometry and X-ray single crystal and powder diffraction. A preliminary catalytic study showed that ester-functionalized complexes 4a and 4b gave rise to highly active catalyst in the double Mizoroki-Heck coupling of aryl dibromides, while the in situ ester-hydrolyzed complexes were also active in the coupling of activated aryl chlorides. 相似文献
18.
A new family of chiral alkoxy-N-heterocyclic carbene (NHC) ligands has been designed for the enantioselective copper-catalyzed conjugate addition of dialkylzincs to enones. These new bidentate NHC ligands were synthesized in high overall yields using a five-step procedure starting from commercially available β-aminoalcohols. Influence of the temperature, base, solvent and copper source were studied in order to optimize the stereoselectivity of the addition. High reactivity and excellent enantioselectivity were obtained at ambient temperature with a range of cyclic enones and dialkylzinc. Addition to acyclic enones has also been studied. 相似文献
19.
A series of simple and new C2-symmetric diphenylmethylidene malonate-type bis(oxazoline) ligands were synthesized and applied to the Friedel-Crafts reaction and allylic alkylation. The Cu(II) complex of ligand 4b bearing the benzyl group afforded good to excellent enantioselectivity for the F-C adducts (up to >99% ee) between indole and alkylidene malonate, and the palladium complex of ligand 4c bearing the phenyl group afforded excellent enantioselectivity (up to 94% ee) for the allylic alkylation product. 相似文献
20.
Chiral imidates were efficiently synthesized in one step and with high yields (seven examples). These chiral imidates were used as ligands in the Cu(I)-catalyzed asymmetric aziridination of methyl cinnamate and in the asymmetric diethylzinc additions to benzaldehyde as a proof of principle. The imidate catalyst system showed high catalytic activities and induced encouraging selectivities. An X-ray structure analysis of an imidate-Cu(I) complex is included, showing a distorted tetrahedral arrangement with two bidentate ligand molecules surrounding the metal. 相似文献