- Asymmetric cyclopropanation and aziridination reactions of olefins catalyzed by Cu(I)-binaphthyldiimine complexes
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The chiral Cu(I)-N,N′-bis(2,6-dichlorobenzylidene)-1,1′-binaphthyl-2, 2′-diamine complex was found to be an efficient catalyst for asymmetric cyclopropanation and aziridination reactions of olefins with l-menthyl diazoacetate and [N-(p-tolylsulfonyl)imino
- Suga, Hiroyuki,Kakehi, Akikazu,Ito, Suketaka,Ibata, Toshikazu,Fudo, Tomomi,Watanabe, Yuzuru,Kinoshita, Yoshinori
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- Synthesis of chiral bis(oxazolinyl)biferrocene ligands and their application to Cu(I)-catalyzed asymmetric cyclopropanation
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Homochiral bis(oxazolinyl)biferrocene ligands, which have both planar and central chirality, are synthesized from oxazolinylferrocenes through a diastereoselective directed lithiation followed by an oxidative dimerization. Asymmetric cyclpropanation of styrene with diazoacetates in the presence of 5 mol% CuOTf-bis(oxazolinyl)biferrocene complexes gives 2-(phenyl)cyclopropane carboxylates in up to 99% ee.
- Kim, Sung-Gon,Cho, Chang-Woo,Ahn, Kyo Han
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- Cu(I)-binaphthyldiimine catalyzed asymmetric cyclopropanation of olefin with diazoacetate
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Chiral 1,1′-binaphthyl-N,N′-bis(2,6-dichloro-benzy-lidene)-2,2′- diamine (1) was found to be an effective ligand for the copper-catalyzed enantioselective cyclopropanation of olefin with l-menthyl diazoacetate. For example, the reaction of 1,1-diphenyleth
- Suga, Hiroyuki,Fudo, Tomomi,Ibata, Toshikazu
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- Synthesis of an Axially Dissymmetric Biphenylcarboxylate Ligand, BDME, and Asymmetric Cyclopropanation of Olefins with Diazoacetate Catalyzed by Its Dirhodium(II) Complex
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An axially dissymmetric biphenylcarboxylate ligand, BDME (4), has been newly designed and prepared. The dirhodium(II) complex (1) of (4) proved to be an excellent catalyst in asymmetric cyclopropanation of styrene with d-menthyl diazoacetate affording d-menthyl cis- 2- phenyl-cyclopropane-1-carboxylate of 99% de.
- Ishitani, Hitoshi,Achiwa, Kazuo
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- Novel chiral bisoxazoline ligands with a biphenyl backbone: Preparation, complexation, and application in asymmetric catalytic reactions
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Novel C2-symmetric chiral bisoxazoline ligands 1 were easily prepared from enantiomerically pure 2-amino alcohols and achiral 2,2′-biphenyldicarboxylic acid via the corresponding amide and mesylate as intermediates. Since these ligands bear only two ortho-substituents on the biphenyl backbone, the biphenyl axis is not fixed, and the two diastereomers of these ligands exist in equilibrium in solution. Interestingly, when the ligands 1 were coordinated with a metal ion, only one of the two possible diastereomer complexes, an (S,aS,S)-complex, can be formed depending on the combination of the ligand and the metal ion. Thus, copper(I) afforded only the (S,a,S,S)-complexes with all ligands 1, while zinc(II), palladium(II), and silver(I) afforded the (S,aS,S)-complexes as the sole product only with 1b, which has a bulky terf-butyl group on the oxazoline ring, and a mixture of the two diastereomer complexes with 1a,c,d. The copper(I)-catalyzed asymmetric cyclopropanation of styrene with diazoacetate proceeded successfully with these ligands and good to excellent enantioselectivities were afforded.
- Imai, Yoshitane,Zhang, Wanbin,Kida, Toshiyuki,Nakatsuji, Yohji,Ikeda, Isao
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- Synthesis of imine-amine type of chiral ligands and their application in the asymmetric cyclopropanation of olefins with diazoacetates
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Novel chiral ligands 1, which possess both imine and amine moieties, were prepared from readily available homochiral materials. Copper complexes of 1 were prepared in situ and used in the asymmetric cyclopropanation of olefins with alkyl diazoacetates to
- Ma, Jun-An,Wang, Li-Xin,Zhang, Wei,Zhou, Qi-Lin
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- Tetrakisdirhodium(II) and Its Catalytic Applications for Metal Carbene Transformations
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The synthesis and X-ray structure of the binuclear complex tetrakisdirhodium(II) (4>) are reported.Structure-selectivity comparisons are made for typical metal carbene transformations, such as inter- and intramolecular cyclopropane formation, intermolecular cyclopropene formation and intramolecular C-H insertions of diazoacetates and diazoacetamides.The enantioselectivity achieved in the 4>-catalyzed reactions is intermediate between that of 4> and 4>, which were described previously (mepy=methyl 5-oxopyrrolidine-2-carboxylate; bnox=4-benzyloxazolidin-2-one).In contrast to other catalyzed intermolecular cyclopropane formations, those using 4> result preferentially in formation of the cis-cyclopropane.
- Doyle, Michael P.,Winchester, William R.,Protopova, Marina N.,Mueller, Paul,Bernardinelli, Gerald,et al.
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- Bisoxazoline ligands with an axial-unfixed biaryl backbone: the effects of the biaryl backbone and the substituent at oxazoline ring on Cu-catalyzed asymmetric cyclopropanation
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The synthesis of novel C2-symmetric bisoxazoline ligands with an axial-unfixed biaryl backbone and different substituents at the oxazoline ring is reported. The diastereomer equilibrium of these ligands in solution and their complexation behavi
- Zhang, Wanbin,Xie, Fang,Matsuo, Shigeaki,Imahori, Yuji,Kida, Toshiyuki,Nakatsuji, Yohji,Ikeda, Isao
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p. 767 - 777
(2007/10/03)
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- Novel chiral dibenzo[a,c]cycloheptadiene bis(oxazoline) and catalytic enantioselective cyclopropanation of styrene
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A series of chiral C2-symmetric bis(oxazoline) ligands containing dibenzo[a,c]cycloheptadiene units were synthesized. The copper complexes, prepared in situ from copper (I)-triflate and the new enantiopure oxazoline ligands, were assessed as chiral catalysts in the enantioselective cyclopropanation of styrene with diazoacetate. Enantioselectivities up to 82 and 62%, respectively, for trans- and cis-2-phenylcyclopropanecarboxylate were observed.
- Du, Da-Ming,Fu, Bin,Hua, Wen-Ting
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p. 1933 - 1938
(2007/10/03)
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- Catalytic asymmetric cyclopropanation of alkenes with diazoesters in protic and biphasic media
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As a C2 symmetric hydrophilic chiral ligand, a series of 2,6-bis(oxazolinyl)-pyridines (pyboxs) bearing a hydroxyalkyl group on the oxazoline ring has been synthesized from readily available amino acid derivatives. Catalytic asymmetric intermolecular cyclopropanation of electron rich terminal alkenes with diazoesters in the presence of hydrophilic pybox ligand, pybox-hm and Ru(II) complex proceeded smoothly in protic or biphasic media to give the corresponding cyclopropanation products in 97:3 to 99:1 trans/cis ratios and 90 to 97% ee. In the case of the intramolecular cyclopropanation reaction of trans-cinnamyl diazoester using Ru(II)(pybox-he) complex in biphasic medium gave the corresponding cyclopropane ring fused lactone in 52% ee. Steric tuning of the chiral environment of pybox ligands was simply achieved by using a weak interaction between the solvent and the hydroxyl groups of the chiral ligand. The solubility of the new hydrophilic pybox and Ru(II) complexes in protic solvents is dramatically increased; hence, the efficiency of these catalysts enhanced the rate of cyclopropanation. Furthermore, the active catalyst in the water phase can be re-used several times for the cyclopropanation reaction.
- Iwasa, Seiji,Tsushima, Shinji,Nishiyama, Kohei,Tsuchiya, Yasunori,Takezawa, Futoshi,Nishiyama, Hisao
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p. 855 - 865
(2007/10/03)
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- In search of high stereocontrol for the construction of cis-disubstituted cyclopropane compounds. Total synthesis of a cyclopropane-configured urea-PETT analogue that is a HIV-1 reverse transcriptase inhibitor.
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[reaction: see text] A new azetidine-ligated dirhodium(II) catalyst that possesses a l-menthyl ester attachment provides significant diastereocontrol and high enantiocontrol for the formation of cis-cyclopropane products from reactions of substituted styr
- Hu, Wenhao,Timmons, Daren J,Doyle, Michael P
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p. 901 - 904
(2007/10/03)
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- Asymmetric cyclopropanation in protic media conducted by chiral bis(hydroxymethyl-dihydrooxazolyl)pyridine-ruthenium catalysts
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Cyclopropanation of styrene with diazoacetates, performed in aqueous/organic biphasic media or homogeneous alcoholic media in the combination of toluene by using chiral bis(hydroxymethyldihydrooxazolyl)pyridine-ruthenium catalyst, resulted in high enantio
- Iwasa,Takezawa,Tuchiya,Nishiyama
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- Asymmetric inter- and intramolecular cyclopropanation of alkenes catalyzed by chiral ruthenium porphyrins. Synthesis and crystal structure of a chiral metalloporphyrin carbene complex
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Extensive investigations of asymmetric intermolecular cyclopropanation of terminal alkenes with diazoacetates catalyzed by ruthenium porphyrin [Ru(P*)(CO)(EtOH)] (1, H2P* = 5,10,15,20-tetrakis-{(1S,4R,5R,8S)-1,2,3,4,5,6,7,8-octahydro-1,4:5,8- dimethanoanthracene-9-yl}porphyrin) and the application of catalyst 1 to asymmetric intramolecular cyclopropanation of allylic or homoallylic diazoacetates are described. The intermolecular cyclopropanation of styrene and its derivatives with ethyl diazoacetate afforded the corresponding cyclopropyl esters in up to 98% ee with high trans/cis ratios of up to 36 and extremely high catalyst turnovers of up to 1.1 × 104. Examination of the effects of temperature, diazoacetate, solvent, and substituent in the intermolecular cyclopropanation reveals that (i) both enantioselectivity and trans selectivity increase with decreasing temperature, (ii) sterically encumbered diazoacetates N2CHCO2R such as R = But, and donor solvents, such as diethyl ether and tetrahydrofuran, are beneficial to the trans selectivity, and (iii) electron-donating para substituents on styrene accelerate the cyclopropanations, with the log(kx/kH) vs σ+ plot for para-substituted styrenes p-X-C6H4CH=CH2 (X = MeO, Me, Cl, CF3) exhibiting good linearity with a small negative ρ+ value of -0.44 ± 0.09. In the case of intramolecular cyclopropanation, complex 1 promoted the decomposition of a series of allylic diazoacetates to form the cyclopropyl lactones in up to 85% ee, contributing the first efficient metalloporphyrin catalyst for an asymmetric intramolecular cyclopropanation. Both the inter- and intramolecular cyclopropanations were proposed to proceed via a reactive chiral ruthenium carbene intermediate. The enantioselectivities in these processes were rationalized on the basis of the X-ray crystal structures of closely related stable chiral carbene complexes [Ru(P*)(CPh2)] (2) and [Ru(P*)(C(Ph)-CO2CH2CH=CH2)] (3) obtained from reactions of complex 1 with N2CPh2 and N2C(Ph)CO2CH2CH=CH2, respectively.
- Che,Huang,Lee,Li,Lai,Kwong,Teng,Lee,Lo,Peng,Zhou
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p. 4119 - 4129
(2007/10/03)
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- First enantioselective catalyst based on a chiral terpyridine: Synthesis of new C2-symmetric 2,2':6',2''-terpyridine ligands and copper-catalyzed enantioselective cyclopropanation of alkenes
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New C2-symmetric chiral 2,2':6',2''-terpyridines were prepared from readily available homochiral materials. Copper complexes of these ligands were prepared in situ and their catalytic activities in cyclopropanations of alkenes with alkyl diazoacetate to give cyclopropyl esters were studied. In all cases, the cyclopropyl ester yields were excellent and enantioselectivities up to 94% ee were observed. Competition experiments revealed that electron-donating substituents on styrene accelerate the reaction. Hammett plot exhibited a good linearity with negative ρ+ value (-0.79). Copyright (C) 2000 Elsevier Science Ltd.
- Kwong, Hoi-Lun,Lee, Wing-Sze
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p. 2299 - 2308
(2007/10/03)
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- Investigation of the Effects of the Structure and Chelate Size of Bis-oxazoline Ligands in the Asymmetric Copper-Catalyzed Cyclopropanation of Olefins: Design of a New Class of Ligands
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A set of novel, C2-symmetric bis-oxazoline ligands has been synthesized by mounting two oxazoline rings onto an optically active 1,3-dioxolane backbone. This design allows for the control of both orientation as well as the proximity of the oxazolinyl R-groups around the reactive site. As a result of the twist imparted by the 1,3-dioxolane ring, the stereogenic oxazolinyl substituents can be brought either toward or away from the complexed metal in a controllable fashion. Starting from L-amino alcohols and either L- or D-tartaric acid, two sets of ligands (6b-e and 7a,b) were synthesized and evaluated in the copper-catalyzed cyclopropanation of olefins. The comparison of benzyl and isopropyl derivatives of these ligands with previously reported five- and six-membered bis-oxazolines clearly indicates the beneficiary effect of the larger chelate size and the chiral tether of the tartrate-derived ligand. The effect of the different oxazolinyl groups along with the different substituents on the dioxolane tethers was also investigated. The influence of the alkyl group of the diazoacetate was studied, and the diazoacetate derived from (-)-8-phenylmenthol was found to be superior to (-)-menthyl diazoacetate. The cyclopropanation of vinyl acetate, a relatively unexplored substrate for this reaction, furnished cyclopropanol derivatives in good optical purity.
- Bedekar, Ashutosh V.,Koroleva, Elise B.,Andersson, Pher G.
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p. 2518 - 2526
(2007/10/03)
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- Asymmetric cyclopropanation of olefins with diazoacetate using chiral copper catalysts
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Chiral 2-(2-aryl- or 2-alkyl-sufonylamino)phenyl-4-phenyl-1,3-oxazolines were found to be effective ligands for copper-catalyzed enantioselective cyclopropanation reaction of olefins. The reaction of styrene with d-menthyl diazoacetate in the presence of optically active copper catalysts gave cyclopropanation products in a ratio of trans: cis = 83: 17 with 63% ee (trans) and 84% ee (cis).
- Ichiyanagi, Tsuyoshi,Shimizu, Makoto,Fujisawa, Tamotsu
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p. 9599 - 9610
(2007/10/19)
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- Dirhodium(II)tetrakis[3(S)-phthalimido-2-piperidinonate]: A novel dirhodium(II) carboxamidate catalyst for asymmetric cyclopropanation
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Dirhodium(II) tetrakis[3(S)-phthalimido-2-piperidinonate] catalyzes cyclopropanation of α-methylstyrene with d-menthyl diazoacetate to give d-menthyl (1S,2S)-2-methyl-2-phenylcyclopropanecarboxylate of 90% de.
- Watanabe, Nobuhide,Matsuda, Hideo,Kuribayashi, Harumi,Hashimoto, Shun-Ichi
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p. 537 - 542
(2007/10/03)
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- C2-Symmetric 1,2-Diamine/Copper(II) Trifluoromethanesulfonate Complexes as Chiral Ctalysts. Asymmetric Cyclopropanations of Styrene with Diazo Esters
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Styrene and diazo esters react in the presence of copper(II) trifluoromethanesulfonate (1 molpercent) and (1S,2S)-N,N'-di(mesitylmethyl)-1,2-diphenyl-1,2-ethanediamine (2-3 molpercent) to give 2-phenyl-1-cyclopropanecarboxylates in good to excellent optical yields.This reaction has been applied to the synthesis of crythanthemic acid.
- Kanemasa, Shuji,Hamura, Satoshi,Harada, Etsuko,Yamamoto, Hidetoshi
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p. 7985 - 7988
(2007/10/02)
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- Asymmetric catalytic cyclopropanation of olefins: Bis-oxazoline copper complexes
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Bis-oxazolines (1-7) prepared from diethyl malonate and chiral amino alcohols were converted into their Cu(II) complexes which, upon activation, exhibit high enantioselectivity of up to 99 %ee for catalytic cyclopropanation of olefins.
- Lowenthal, Richard E.,Abiko, Atsushi,Masamune, Satoru
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p. 6005 - 6008
(2007/10/02)
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- Semicorrin Metal Complexes as Enantioselective Catalysts. Part 2. Enantioselective Cyclopropane Formation from Olefins with Diazo Compounds Catalyzed by Chiral (Semicorrinato)copper Complexes)
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Copper complexes of chiral, C2-symmetric semicorrin ligands were found to be efficient catalysts for the cyclopropane formation from olefins with diazo compounds.In the presence of 1 mol-percent of catalyst, alkyl diazoacetates reacted smoothly with termi
- Fritschi, Hugo,Leutenegger, Urs,Pfaltz, Andreas
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p. 1553 - 1565
(2007/10/02)
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