共查询到20条相似文献,搜索用时 15 毫秒
1.
Zi-Bo Li 《Tetrahedron letters》2005,46(13):2223-2226
The BINOL-salen compound (S)-5c in combination with Ti(OiPr)4 is found to catalyze the addition of TMSCN to aldehydes to form chiral cyanohydrins with very good enantioselectivity (75-85% ee). The reactions are carried out in one-pot at room temperature without the need to isolate the chiral Lewis acid catalyst. 相似文献
2.
Several chiral Schiff base ligands derived from α-amino acids were prepared, and zinc complexes with these chiral Schiff base ligands prepared were tested for the catalytic asymmetric hydrosilylation of ketones, and the results showed that excellent ee values were obtained, which are the prominent examples of catalytic asymmetric hydrosilylation of ketones catalyzed with zinc complexes in the presence of readily available and inexpensive α-amino acids based Schiff base ligands. 相似文献
3.
A BINOL-derived diphosphonite having a xanthene backbone is an excellent bidentate ligand in Ru-catalyzed 2-propanol-based transfer hydrogenation of aryl/alkyl and alkyl/alkyl ketones (ee = 76-99%). Even notoriously difficult ketones such as isopropyl methyl ketone are reduced with extraordinarily high enantioselectivity (ee = 99%). 相似文献
4.
Anthony G. Coyne 《Tetrahedron letters》2007,48(5):747-750
The HETPHOX ligand class was applied to the rhodium-catalysed asymmetric hydrosilylation of a range of substituted acetophenones. Enantioselective hydrosilylation of acetophenone with the tert-butyl substituted HETPHOX ligand gave (R)-phenylethanol in excellent enantioselectivity (84% ee) and in good conversion (80%). When applied to the hydrosilylation of other ketones conversions up to 93% and enantioselectivities up to 88% were observed. 相似文献
5.
The combination of Fe(OAc)2 and multi-nitrogen-based ligands such as N,N,N',N'-tetramethyethylenediamine, bis-tert-butyl-bipyridine, or bis(oxazolinyl)pyridine can efficiently catalyse hydrosilylation of ketones to give the corresponding alcohols in high yields including asymmetric catalysis. 相似文献
6.
Rajesh S. Bhosale Suresh S. Ardhapure Sudhakar R. Bhusare 《Tetrahedron letters》2005,46(42):7183-7186
The use of molecular iodine as the catalyst for a one-pot synthesis of quinoxaline derivatives at room temperature is reported. 相似文献
7.
8.
《Tetrahedron: Asymmetry》2005,16(23):3877-3880
A series of thioether–phosphinite ligands, easily prepared in a few steps from inexpensive d-(+)-xylose, were tested in the Rh-catalyzed hydrosilylation of ketones. Systematic variation of the electronic and steric properties of the thioether moiety provided useful information about the ligand parameters which control enantiodiscrimination. The results show that the enantiomeric excesses are strongly dependent on the steric properties of the substituent on the thioether moiety and on the steric properties of the substrate. High activities and good enantiomeric excesses (up to 90%) were obtained in the hydrosilylation of several aryl ketones. 相似文献
9.
Helen L. Ngo 《Tetrahedron letters》2005,46(4):595-597
Polar bisphosphonic acid-derived Ru(BINAP)(DPEN)Cl2 precatalysts were synthesized and immobilized in room temperature ionic liquids (RTILs) for asymmetric hydrogenation of aromatic ketones with ee values of up to 98.7%. The performance of the Ru catalysts is highly dependent on the nature of imidazolium ILs. For the imidazolium ILs without acidic protons, both ILs and Ru catalysts were recycled by simple extraction and reused. Such a simple immobilization approach also prevented the leaching of Ru (and Ru catalysts) into the chiral secondary alcohol products, and should prove desirable for the production of pharmaceutical intermediates that are free from metal contaminants. 相似文献
10.
11.
[reaction: see text] Catalytic systems generated in situ from the chiral PNNP ligands with iridium or rhodium hydride complexes exhibited excellent catalytic activity and good enantioselectivity in the asymmetric transfer hydrogenation of aromatic ketones without added base. The best result was obtained in the IrH(CO)(PPh(3))(3)-ligand 2 catalytic system with up to 99% yield and 97% ee. 相似文献
12.
Radhakrishnan Mahesh Arghya Kusum Dhar Tara Sasank T.V.N.V. Sappanimuthu Thirunavukkarasu Thangaraj Devadoss 《中国化学快报》2011,22(4):389-392
The condensation of o-phenylenediamines with 1,2-dicarbonyl compounds in the presence of citric acid afforded the corresponding quinoxaline derivatives in higher yields at room temperature in ethanol,and most of the reactions were completed in less than 1 min. 相似文献
13.
14.
[reaction: see text] Cyclopalladated compounds derived from the ortho-metalation of benzylic tert-butyl thioethers are excellent catalyst precursors for the Suzuki cross-coupling reaction of aryl bromides and chlorides with phenylboronic acid under mild reaction conditions. A broad range of substrates and functional groups are tolerated in this protocol, and highly catalytic activity is attained. 相似文献
15.
In situ generation of CuH ligated by Takasago's new nonracemic ligand, DTBM-SEGPHOS, leads to an especially reactive reagent capable of effecting asymmetric hydrosilylation of heteroaromatic (H) ketones under very mild conditions. PMHS serves as an inexpensive source of hydride. Substrate-to-ligand ratios on the order of 2000:1 are employed. [reaction: see text] 相似文献
16.
The influence of structural modifications of the diamine ligand and the ZnR2 precursor in the [ZnR2-diamine]-catalyzed asymmetric hydrosilylation of prochiral ketones with PMHS in aprotic medium is reported. A new diamine ligand giving up to 91% ee in the reduction of acetophenone is described. The scope of this reduction system has been investigated using variously functionalized ketones and some deactivation pathways have been identified. 相似文献
17.
An efficient one-pot synthesis of polyhydroquinolines by four-component coupling reactions of aldehydes, ethyl acetoacetate, dimedone and ammonium acetate in the presence of HY-zeolite at ambient temperature has been achieved. The conversions took shorter times to form the products in excellent yields. HY-zeolite can be recovered and reused. 相似文献
18.
19.
Gayatri Sarmah Saitanya K. Bharadwaj Anindita Dewan Ankur Gogoi Utpal Bora 《Tetrahedron letters》2014
A simple and efficient vanadium based catalyst system for the oxidation of primary and secondary alcohols to aldehydes or ketones is reported using tert-butyl hydroperoxide as oxidizing agent and vanadyl sulfate as catalyst at room temperature. The versatility of the catalytic protocol is studied with wide variety of substrates. 相似文献
20.
Because of the intrinsic advantages, Suzuki coupling reactions have been one of the most popular coupling reactions in organic synthesis, however developing a high-performance heterogeneous catalyst for Suzuki coupling reactions in aqueous media at low temperature (e.g. room temperature) is still a challenge. Herein, a heterogeneous catalyst with coordinated Pd as active site and a designed conjugated phenanthroline based porous polymer (CPP) as support was fabricated. Systematically investigation on CPP support by Fourier transform infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), Transmission electron microscopy (TEM), N2 adsorption–desorption isotherm and Scanning electron microscopy (SEM) show that the derived CPP catalyst support owns a porous structure, moderately good surface area (141 m2/g) and an excellent thermal stability. As a heterogeneous catalyst for the synthesis of biphenyl derivatives via Suzuki coupling, Pd/CPP achieves an excellent catalytic performance and recycling ability towards Suzuki reaction of various reactants at room temperature in ethanol-water medium. 相似文献