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Rukhsana I. Kureshy K. Jeya Prathap Tamal Roy Nabin Ch. Maity Noor‐ul H. Khan Sayed H. R. Abdi Hari C. Bajaj 《Advanced Synthesis \u0026amp; Catalysis》2010,352(17):3053-3060
A series of new recyclable chiral dicationic chromium(III) salen complexes 1 – 10 bearing different substituents, viz., hydrogen, methyl, tert‐butyl, triphenylphosphinomethyl, triethylaminomethyl, methylimidazolium, methylpyridinium, methyl‐N,N‐dimethylpyridinium at the 3,3′‐ and 5,5′‐ positions of the salen unit with (1S,2S)‐(+)‐1,2‐diaminocyclohexane, (1S,2S)‐(−)‐1,2‐diphenyl‐1,2‐diaminoethane, and (S)‐(−)‐1,1′‐binaphthyl‐2,2′‐diamine collars have been synthesized and characterized by various physico‐chemical methods. These complexes were used as catalysts for the highly enantioselective aminolytic kinetic resolution of racemic trans‐epoxides with different anilines as nucleophiles at room temperature. With the use of catalyst 3 , anti‐β‐amino alcohols were obtained in excellent yields (>99% with respect to the nucleophile) and enantioselectivities (ee>99%) with the concomitant recovery of corresponding epoxides in high optical purity (ee up to >99%) and quantitative yields in 12 h. The catalyst 3 is recyclable in the aminolytic kinetic resolution process and worked well up to six cycles with retention of enantioselectivity. 相似文献
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Poly(4‐vinylimidazolium)s, derived from the self‐immobilization of 4‐vinylimidazoliums, with diazabicyclo[5.4.0]undec‐7‐ene (DBU) and zinc bromide (ZnBr2) are used as a highly efficient catalyst for the chemical fixation of carbon dioxide. This catalytic system has been applied for the preparation of cyclic carbonates from terminal epoxides and carbon dioxide. Many functional groups, including chloro, vinyl, ether, and hydroxy groups are well tolerated in the reactions. Moreover, the catalytic system was found to catalyze the conversion of more sterically congested epoxides which are generally considered to be challenging substrates for fabricating the cyclic organic carbonates. In addition, the disubstituted epoxides are found to react with retention of configuration. The polymer precatalyst is easily recovered and reused. A plausible reaction mechanism is proposed.
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Maurizio Benaglia Giuseppe Celentano Mauro Cinquini Alessandra Puglisi Franco Cozzi 《Advanced Synthesis \u0026amp; Catalysis》2002,344(2):149-152
A tyrosine‐derived imidazolidin‐4‐one was immobilized on a modified poly(ethylene glycol) and converted in situ into a soluble polymer‐supported catalyst for the enantioselective Diels–Alder cycloaddition of acrolein to 1,3‐cyclohexadiene (up to 92% ee) and 2,3‐dimethyl‐1,3‐butadiene (73% ee). Catalyst recycling (up to four cycles) was accompanied by some loss of the chemical efficiency and marginal erosion of the enantioselectivity. 相似文献
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MichaelP. Doyle Ming Yan IainM. Phillips DarenJ. Timmons 《Advanced Synthesis \u0026amp; Catalysis》2002,344(1):91-95
N‐Benzyl‐2‐deoxyxylonolactams are accessible by highly chemoselective, diastereoselective, and enantioselective carbon‐hydrogen insertion reactions of diazoacetamides. Competing aromatic cycloaddition or β‐lactam formation via carbon‐hydrogen insertion into a benzylic position can be minimized by the proper selection of chiral catalyst. Conformational influences are important in product preference. 相似文献
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Cross‐linked polymeric ionic liquid material‐supported copper (Cu‐CPSIL), imidazolium‐loaded Merrifield resin‐supported copper (Cu‐PSIL) and silica dispersed CuO (CuO/SiO2), were prepared and proved to be efficient catalysts for the one‐pot synthesis of 1,4‐disubsituted‐1,2,3‐triazoles by the reaction of alkyl halides with sodium azide and terminal alkynes in water at room temperature. Moreover, these supported copper catalysts were recovered quantitatively from the reaction mixture by simple filtration and reused for five consecutive recycles without significant loss of catalytic activity. Among the three immobilized copper catalysts, Cu‐CPSIL exhibited excellent catalytic activity for the reaction of aliphatic bromides, sodium azide and terminal alkynes. The differences in the catalytic performances of the catalysts could be ascribed to the copper dispersion and the interaction between copper and the supports. In addition, water was used as the reaction media and the proton provider, the latter was found to be very important for the reaction. The XPS results suggested that the supported Cu(II) catalysts were reduced to catalytic Cu(I) species via alkynes homocoupling reaction. By means of IR and ESI‐MS studies, a possible mechanism of cycloaddition based on the reduction of Cu(II) to Cu(I) species was proposed. 相似文献
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A chiral, bimetallic cobalt(III)salen‐calix[4]arene hybrid structure was prepared and tested in the hydrolytic kinetic resolution (HKR) of racemic epoxides. Kinetic studies have revealed that the two catalytic units on the upper rim of the calixarene scaffold are able to activate the reactants in a cooperative and primarily intramolecular mode. High enantioselective behaviour was observed and besides, a higher stability was found for the bimetallic catalyst as compared to a monometallic reference complex. 相似文献
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RaymondE. Forslund James Cain John Colyer MichaelP. Doyle 《Advanced Synthesis \u0026amp; Catalysis》2005,347(1):87-92
The [2+2]‐cycloaddition reaction between ethyl glyoxylate and trimethylsilylketene is reported. Enantiomeric excesses up to 83% have been achieved with the use of only 1.0 mol % of a previously unreported chiral imidazolidinone‐ligated dirhodium(II) carboxamidate catalyst. An extensive survey of chiral catalysts has shown that enantiocontrol for cycloaddition increases as the steric bulk of the ligand is increased. However, enantioselectivity is increased to 99% ee by the addition of 10 mol % of quinine as a co‐catalyst with a chiral dirhodium(II) azetidinone‐ligated catalyst, and there is a significant decrease in reaction time. 相似文献
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Co/AlN/SiO2 catalysts were prepared by the saturative chemisorption of cobalt(III) acetylacetonate (Co(acac)3). The support was bare silica or silica that had been modified with aluminum nitride (AlN) by repeated separate, saturated chemisorptions of trimethylaluminum and ammonia two or six times. Chemisorption of Co(acac)3 occurred on all the supports up to a saturation ligand density of 2.7 acac nm-2; the amount of bonded cobalt decreased from 2.1 to 1.5 atCo nm-2 with increasing extent of AlN modification of the support. Ligand exchange reaction, releasing Hacac, occurred less on AlN-modified silica than on bare silica. This induced difference in the reduction behavior of the catalysts, and catalytic activity in gas-phase hydroformylation of ethene, was lower with Co/AlN/SiO2 than with Co/SiO2 catalyst. 相似文献
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Tatsuo Niimi Tatsuya Uchida Ryo Irie Tsutomu Katsuki 《Advanced Synthesis \u0026amp; Catalysis》2001,343(1):79-88
Cyclopropanation of styrene derivatives with alkyl α‐diazoacetate in the presence of the second‐generation (salen)cobalt(II) complex 6 proceeded with excellent cis‐ and enantioselectivity. On the other hand, the cyclopropanation in the presence of complex 14 which was designed on the basis of the mechanism of asymmetric induction by complex 6 showed good trans‐ and excellent enantioselectivity. 相似文献
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Kyoung‐Chan Lim Young‐Taek Hong Sunggak Kim 《Advanced Synthesis \u0026amp; Catalysis》2008,350(3):380-384
Using the C2‐symmetric bis‐oxazoline copper(II) catalyst 6f as a chiral Lewis acid, α′‐phosphoric enones 2 undergo 1,3‐dipolar cycloaddition with nitrones 3 to provide isoxazolidines 4 with very high enantioselectivity and endo/exo selectivity. 相似文献
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Dongmin Zhao Jiquan Zhao Shanshan Zhao Weiyu Wang 《Journal of Inorganic and Organometallic Polymers and Materials》2007,17(4):653-659
A chiral Manganese (III) salen complex was immobilized on the walls of MCM-41 (mobile crystalline material) through the multi-grafting
method. The immobilized complex was characterized by XRD, FTIR, UV-Vis, ICP and Nitrogen sorption, and was applied to the
asymmetric epoxidation of unfuctionalized alkenes including 1,2-dihydronaphthalene, α-methylstyrene, cis-β-methylstyrene, styrene using NaClO and m-chloroperbenzoic acid (m-CPBA) as oxidants respectively. The immobilized complex showed good activity and enantioselectivity in the epoxidation of
1,2-dihydronaphthalene by using NaClO as oxidant. It could also be run for 4 times in the epoxidation of α-methylstyrene without
obvious loss of activity or enantiomeric excess. 相似文献
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Liang Wei Zuo‐Fei Wang Lu Yao Guofu Qiu Haiyan Tao Hua Li Chun‐Jiang Wang 《Advanced Synthesis \u0026amp; Catalysis》2016,358(24):3955-3959
An unprecedented copper(II)‐catalyzed enantioselective 1,3‐dipolar [3+4] cycloaddition of azomethine imines with in situ formed azoalkenes has been realized. This strategy provides a facile access to biologically important 1,2,4,5‐tetrazepine derivatives in high yield with exclusive regioselectivity and high stereoselectivity. Moreover, enantioenriched azomethine imines could be obtained via an efficient kinetic resolution using the same approach.
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Chiral N‐(binaphthyl‐2‐yl)thiophosphoramide L7 [O,O‐diethyl 2′‐(ethylamino)‐1,1′‐binaphthyl‐2‐ylamidothiophosphate] prepared from the reaction of diethyl chlorothiophosphate with (R)‐(+)‐N‐ethyl‐1,1′‐binaphthyl‐2,2′‐diamine was used as a catalytic chiral ligand in the first Cu(OTf)2‐promoted catalytic asymmetric addition of diethylzinc to N‐(diphenylphosphinoyl) imines in which ~85% ee can be realized. 相似文献
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Luca Bernardi Mauro Comes‐Franchini Mariafrancesca Fochi Virginia Leo Andrea Mazzanti Alfredo Ricci 《Advanced Synthesis \u0026amp; Catalysis》2010,352(18):3399-3406
The catalytic asymmetric inverse‐electron‐demand (IED) [4+2] cycloaddition of various salicylaldehyde‐derived N‐arylimines with electron‐rich alkenes in the presence of chiral BINOL‐derived phosphoric acid catalysts has been studied with the aim of obtaining optically active 4‐aminobenzopyran derivatives. Dienophiles such as 2,3‐dihydro‐2H‐furan, benzyl N‐vinylcarbamate and 2‐vinylindole have been employed. 相似文献
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The chiral sulfonamide‐thiophosphoramide ligand L1 , prepared from the reaction of (1R,2R)‐(−)‐1,2‐cyclohexanediamine with diphenylthiophosphoryl chloride and p‐toluenesulfonyl chloride, was used as a chiral ligand in Cu(MeCN)4ClO4‐promoted catalytic asymmetric addition of diethylzinc to cyclic enones using LiCl as an additive in which up to 90% ee can be realized under mild conditions within 0.5 h. This chiral ligand is stable and recoverable after usual work‐up and can be reused in the same catalytic asymmetric reaction. Moreover, it was found that this series of chiral ligands represents a type of S,O‐bidentate ligands on the basis of 1H NMR, 31P NMR and 13C NMR spectroscopic investigations. The linear effect of ligand ee and product ee further revealed that the active species is a monomeric Cu(I) complex bearing a single ligand. 相似文献
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The environmentally benign polymerization of aniline provided polyaniline with an emeraldine structure by using iron(III) and ozone which is easily converted from oxygen in air. The influence of the reaction temperature upon the molecular weight of the polyaniline in this system is different from that in the polymerization of aniline using ammonium peroxodisulfate as an oxidant. Although the polyaniline prepared here has low molecular weight, the low molecular weight of the polyaniline does not significantly influence the electrical conductivity of cast films. In contrast, this can provide an advantage for the engineering of polyaniline through solution‐processing. Kinetics of oxidation reactions in the polymerization, systematically investigated here, has revealed that polyaniline is produced catalytically in terms of iron(III) and that an oxidation reaction of iron(II) to iron(III) could be a rate‐determining step in the polymerization. 相似文献
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Anna Falk Lukas Fiebig Jrg‐Martin Neudrfl Andreas Adler Hans‐Günther Schmalz 《Advanced Synthesis \u0026amp; Catalysis》2011,353(18):3357-3362
The use of modular α,α,α′,α′‐tetraaryl‐1,3‐dioxolane‐4,5‐dimethanol (TADDOL)‐ and 1,1′‐bi‐2‐naphthol (BINOL)‐derived phosphine‐phosphite ligands (L2*) in the asymmetric rhodium‐catalyzed intramolecular [4+2] cycloaddition (“neutral” Diels–Alder reaction) of (E,E)‐1,6,8‐decatriene derivatives (including a 4‐oxa and a 4‐aza analogue) was investigated. Initial screening of a small ligand library led to the identification of a most promising, TADDOL‐derived ligand bearing a phenyl group adjacent to the phosphite moiety at the arene backbone. In the course of further optimization studies, the formation of a new, more selective catalyst species during the reaction time was observed. By irradiating the pre‐catalyst with microwaves prior to substrate addition high enantioselectivities (up to 93% ee) were achieved. The new cyclization protocol was successfully applied to all three substrates investigated to give the bicyclic products in good yield and selectivity. 31P NMR and ESI‐MS measurements indicated the formation of a [Rh(L2*)2]+ species as the more selective (pre‐) catalyst. 相似文献