- Enantiopure Fluorous Bis(oxazolines): Synthesis and Applications in Catalytic Asymmetric Reactions
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Various enantiopure fluorous bis(oxazolines) with fluorine content between 52.7 and 58.7% have been synthesized by a simple reaction sequence that involved the introduction of two fluorinated ponytails by alkylation of the corresponding nonfluorous bis(ox
- Bayardon, Jerome,Sinou, Denis
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- The Asymmetric Kharasch Reaction. Catalytic Enantioselective Allylic Acyloxylation of Olefins with Chiral Copper(I) Complexes and tert-Butyl Perbenzoate
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Olefins were treated with tert-butyl perbenzoate in the presence of chiral copper(I) triflate bisoxazoline complexes to give non-racemic allyl benzoates as products.The yields range from 34 to 62percent and the enantiometric excess from 30 to 81percent.A
- Andrus, Merritt B.,Argade, Ankush B.,Chen, Xi,Pamment, Michael G.
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- A reusable enantioselective catalytic system for the Kharasch-Sosnovsky allylic oxidation of alkenes based on a ditopic azabis(oxazoline) ligand
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An easily recoverable and reusable enantioselective catalytic system based on the self-assembly of a coordination polymer through the use of a chiral ditopic ligand, is described for the allylic oxidation of cycloalkenes with tert-butyl perbenzoate. Upon
- Aldea, Luis,Delso, Ignacio,Hager, Markus,Glos, Martin,García, José I.,Mayoral, José A.,Reiser, Oliver
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- New chiral bidentate ligands containing thiazolyl and pyridyl donors for copper-catalyzed asymmetric allylic oxidation of cyclohexene
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Chiral bidentate ligands 1-3, which contain a combination of thiazolyl and pyridyl donors units, were prepared. The syntheses are facile and being based on Kr?hnke condensation of a pinene derivative to form the pyridine ring. Modification at the 8-positi
- Teng, Pang-Fei,Tsang, Chui-Shan,Yeung, Ho-Lun,Wong, Wing-Leung,Kwong, Hoi-Lun,Williams, Ian D.
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- Applications of enantiopure 4,5-diphenyl substituted box and pybox ligands in asymmetric catalysis
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Enantioselectivities of 95-98% have been obtained in the palladium-catalyzed alkylation of rac-3-acetoxy-1,3-diphenyl-1-propene with dimethyl malonate using 4,5-diphenyl substituted bis(oxazoline) as the chiral ligands, whatever the configuration at C-5.
- Bayardon, Jerome,Sinou, Denis,Guala, Matilde,Desimoni, Giovanni
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- Synthesis of Selenium-containing Binaphthyls and their Application to the Asymmetric Ring-opening of Cyclohexene Oxide
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Three novel selenium-containing binaphthyl compounds (1-3) have been synthesized in optically active form and applied to the asymmetric ring-opening reaction of cyclohexene oxide (4), resulting in enantiomeric excesses of between 16 and 50percent.
- Tomoda, Shuji,Iwaoka, Michio
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- Multiphase enantioselective Kharasch-Sosnovsky allylic oxidation based on neoteric solvents and copper complexes of ditopic ligands
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Recoverable multiphase enantioselective catalytic systems for the Kharasch-Sosnovsky oxidation of cycloalkenes with tert-butyl peroxybenzoate are described, based on the use of [BMIM][PF6] and a new solvent derived from glycerol as the catalyst
- Aldea, Luis,Garcia, Jose I.,Mayoral, Jose A.
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- Catalytic enantioselective allylic oxidation of olefins with copper complexes of chiral nonracemic bis(oxazolinyl)pyridine type ligands
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Olefins, on treatment with tert-butyl perbenzoate in the presence of a catalytic amount of chiral copper bis(oxazolinyl)pyridine complexes, gave optically active allylic benzoates. A variety of cyclic olefins were tried in the reaction and a maximum of 81
- DattaGupta, Arpita,Singh, Vinod K.
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- Asymmetric allylic oxidation reactions catalyzed by a chiral nonracemic and C2-symmetric 2,2′-bipyridyl copper(i) complex
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Chiral, nonracemic and C2-symmetric 2,2'-bipyridyl ligand in copper(I)-catalyzed asymmetric allylic oxidation reactions of three cyclic alkenes 2a-c (n=1 -3) with tert-butyl peroxybenzoate, was analyzed. The active copper(I)-catalyst for these
- Lyle, Michael P. A.,Wilson, Peter D.
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- Chiral bipyridine-copper(I) complex-catalyzed enantioselective allylic oxidation of cyclic alkenes
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Chiral copper(I)-bipyridine complexes were prepared and used as catalysts in the enantioselective allylic oxidation of cyclic alkenes with tert-butyl perbenzoate. The yields ranged from moderate to good and enantioselectivities up to 70% were observed.
- Lee, Wing-Sze,Kwong, Hoi-Lun,Chan, Hoi-Ling,Choi, Wing-Wai,Ng, Lai-Yuen
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- Asymmetric Kharasch Reaction: Catalytic Enantioselective Allylic Oxidation of Olefins Using Chiral Pyridine Bis(diphenyloxazoline) - Copper Complexes and tert-Butyl Perbenzoate
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Copper complexes of chiral pyridine bis(diphenyloxazoline)-type ligands have been studied as catalysts for the enantioselective allylic oxidation of olefins. Using 2.5-5 mol % of these chiral catalysts and tert-butyl perbenzoate as oxidant, optically active allylic benzoates were obtained in up to 86% ee. A variety of copper salts was studied under different conditions and in different solvents. Acetone was found to be a superior solvent for the reaction. Use of phenylhydrazine in conjunction with the chiral copper complex played a crucial role in increasing the rate of the reaction. Use of 4 ? molecular sieves increased the optical yield of product in almost every case.
- Sekar, Govindasamy,Dattagupta, Arpita,Singh, Vinod K.
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- Amino acid/copper-catalyzed enantioselective allylic benzoyloxylation of olefins in water promoted by diethylene glycol
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Amino acids, mainly L-proline, in association with diethylene glycol and copper salts have been used in water for a recyclable enantioselective version of the Kharasch-Sosnovsky reaction with e.e.s up to 42%.
- Le Bras, Jean,Muzart, Jacques
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- Chiral, bicyclic proline derivatives and their application as ligands for copper in the catalytic asymmetric allylic oxidation of olefins
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The preparation of the unnatural, bicyclic α-amino acids 7 and 8 is described, along with their utility as chiral ligands in the copper-catalyzed enantioselective allylic oxidation of cyclohexene with tert-butyl perbenzoate. These bicyclic amino acids wer
- Soedergren, Mikael J.,Andersson, Pher G.
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- Asymmetric allylic oxidation of cycloalkenes using a tridentate tris(oxazoline) ligand as a chiral auxiliary
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A tridentate tris(oxazoline) ligand (4b) was found to be an efficient chiral auxiliary for copper-mediated asymmetric allylic oxidation (Kharash- Sosnovsky reaction) of cycloalkenes. Regardless of the ring size of the substrate, the reaction examined showed good enantioselectivity higher than 81% ee. (C) 2000 Elsevier Science Ltd.
- Kohmura, Yoshinori,Katsuki, Tsutomu
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- Immobilization of (l)-valine and (l)-valinol on SBA-15 nanoporous silica and their application as chiral heterogeneous ligands in the Cu-catalyzed asymmetric allylic oxidation of alkenes
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SBA-15 nanoporous silica was synthesized by hydrothermal method using P123 surfactant and tetraethoxyortosilicate in acidic condition and then functionalized by 3-chloropropyltrimethoxysilane. Next, by immobilization of chiral amino acid (S)-2-amino-3-methyl butanoic acid (l-valine) and chiral amino alcohol (S)-2-amino-3-methylbutane-1-ol (l-valinol), preparedviathe reduction ofl-valine by NaBH4/I2in THF, on functionalized-SBA-15, chiral heterogeneous ligands AL*-i-Pr-SBA-15 and AA*-i-Pr-SBA-15 were prepared and characterized by FT-IR, XRD, TGA, EDX, SEM, BET-BJH techniques. The asymmetric allylic oxidation of alkenes was done using copper-complexes of these ligands and the as-synthesized peresters. The reactions were optimized by varying various parameters such as temperature, solvent, amount of chiral heterogeneous ligand, as well as the type and amount of copper salt. Under optimized conditions, 6 mg of AL*-i-Pr-SBA-15 and 3.2 mol% of Cu(CH3CN)4PF6in acetonitrile at 50 °C, the chiral allylic ester was obtained with 80% yield and 39% enantiomeric excess in 24 h. The recyclability of the chiral heterogeneous catalysts was also evaluated without significant reduction in the reaction results up to three runs.
- Samadi, Saadi,Ashouri, Akram,Rashid, Hersh I,Majidian, Shiva,Mahramasrar, Mahsa
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p. 17630 - 17641
(2021/10/04)
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- Designing chiral amido-oxazolines as new chelating ligands devoted to direct Cu-catalyzed oxidation of allylic C–H bonds in cyclic olefins
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A new type of amido-oxazoline ligands was conveniently synthesized from inexpensive and commercially available materials in high yields and enantiomeric excesses. The corresponding chiral copper complexes with this class of ligands [C2 symmetric S,S-bis(amido-oxazoline-Cu(II) complex] were synthesized accordingly. The ORTEP diagram of ligand 6a and complex 6a-copper were compared and characterization of the complex confirmed the involvement of both dentate parts of the ligands, the oxygen and nitrogen atoms, in complexation with copper. The utilization of this amido-oxazoline ligands in the copper-catalyzed enantioselective esterification of allylic C–H bonds of cyclic olefins with tert-butyl-4-nitrobenzoperoxoate resulted in the highest activities, yields (up to 95%) and enantioselectivities (up to 96%) in the presence of HZSM-5 zeolite. These new findings highlight the protocol as one of the most attractive and useful methods for the oxidation of the asymmetric allylic C–H bond of cycloalkenes compared to other methodologies reported in the literature.
- Samadi, Saadi,Jadidi, Khosrow,Samadi, Mojgan,Ashouri, Akram,Notash, Behrouz
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p. 862 - 867
(2019/01/08)
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- Copper(II) complexes of pyridine-oxazoline (Pyox) ligands: Coordination chemistry, ligand stability, and catalysis
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The coordination chemistry of copper(II) complexes bearing pyridine-oxazoline ("Pyox") ligands has been studied, with an aim of investigating their catalytic ability. Interestingly, the stability of the coordinated ligands has been shown to be much less than previously assumed: hydrolysis of the ligands by fortuitous water gives rise to 2-pyridine carboxylate formation, which encapsulate the copper in a two-dimensional coordination polymer 3. The complexes [Cu(R-Pyox)(NCMe)2(ClO4)2] {R = benzyl (Bn) 2a, phenyl (Ph) 2b, isopropyl (iPr) 2c} have been prepared, of which the benzyl derivative has been analysed by CW EPR spectroscopy. The complex [Cu(Bn-Pyox)(NCMe)2(ClO4)2] and the afore-mentioned coordination polymer have been crystallographically characterised. The performance of complexes 2a-c in the asymmetric allylic oxidation of cyclohexene is described.
- Hallett, Andrew J.,O'Brien, Thomas M.,Carter, Emma,Kariuki, Benson M.,Murphy, Damien M.,Ward, Benjamin D.
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- Screening of N,N-bidentate and N,N,Ntridentate pyridine-based ligands in the catalytic allylic oxidation of cyclic olefins
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A variety of chiral N,N-bidentate and N,N,N-tridentate ligands based on the pyridine framework, namely C2-symmetric dipyridylmethane and terpyridine, N-(p-toluensulfinyl)iminopyridines and two kinds of iminopyridines, has been assessed in the asymmetric c
- Solinas, Maurizio,Sechi, Barbara,Chelucci, Giorgio
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p. 831 - 834
(2015/03/04)
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- Screening of N,N-bidentate and N,N,N-tridentate pyridine-based ligands in the catalytic allylic oxidation of cyclic olefins
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A variety of chiral N,N-bidentate and N,N,N-tridentate ligands based on the pyridine framework, namely C2-symmetric dipyridylmethane and terpyridine, N-(p-toluensulfinyl)iminopyridines and two kinds of iminopyridines, has been assessed in the asymmetric c
- Solinasa, Maurizio,Sechia, Barbara,Chelucci, Giorgio
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p. 831 - 834
(2015/02/19)
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- Diversity-oriented enantioselective synthesis of highly functionalized cyclic and bicyclic alcohols
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The copper-catalyzed hetero-allylic asymmetric alkylation (h-AAA) of functionalized Grignard reagents that contain alkene or alkyne moieties has been achieved with excellent regio- and enantioselectivity. The corresponding alkylation products were further transformed into a variety of highly functionalized cyclic and bicyclic alcohols with excellent control over the chemo-, regio-, and stereoselectivity. Copyright
- Mao, Bin,Fa?anás-Mastral, Martín,Lutz, Martin,Feringa, Ben L.
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p. 761 - 770
(2013/02/23)
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- Chemoenzymatic synthesis of chiral 2,2′-bipyridine ligands and their N-oxide derivatives: Applications in the asymmetric aminolysis of epoxides and asymmetric allylation of aldehydes
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A series of enantiopure 2,2′-bipyridines have been synthesised from the corresponding cis-dihydrodiol metabolites of 2-chloroquinolines. Several of the resulting hydroxylated 2,2′-bipyridines were found to be useful chiral ligands for the asymmetric amino
- Boyd,Sharma,Sbircea,Murphy,Malone,James,Allen,Hamilton
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supporting information; experimental part
p. 1081 - 1090
(2010/06/13)
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- New pinene-derived pyridines as bidentate chiral ligands
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A synthesis of new bidentate pyridines 8a-d, 9, and 10 has been developed, starting from triflate 14, readily available from β-pinene 11. A copper complex of the pyridine-oxazoline ligands 8a has been found to catalyze asymmetric allylic oxidation of cyclic olefins 36a-c with good conversion rates and acceptable enantioselectivity (≤67% ee). The imidazolium salt 10 has been identified as a precursor of the corresponding N,N′-unsymmetrical N-heterocyclic carbene ligand, whose complex with palladium catalyzed the intramolecular amide enolate α-arylation leading to oxindole 45 in excellent yield but with low enantioselectivity.
- Malkov, Andrei V.,Stewart-Liddon, Angus J.P.,Teply, Filip,Kobr, Luká?,Muir, Kenneth W.,Haigh, David,Ko?ovsky, Pavel
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p. 4011 - 4025
(2008/09/20)
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- Synthesis of novel C3 symmetric tris(thiazoline) ligands and their application in the allylic oxidation reaction
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A series of novel C3 symmetric tris(thiazoline) ligands were synthesized from trimethyl nitrilotriacetate and an enantiomerically pure amino alcohol via an efficient route. Compound 7a showed moderate to good catalytic enantioselectivity for th
- Cheng, Xue-Ming,Zheng, Zhong-Bo,Li, Nan,Qin, Zhao-Hai,Fu, Bin,Wang, Neng-Dong
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scheme or table
p. 2159 - 2163
(2009/04/11)
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- Novel N,N-bidentate ligands for enantioselective copper(I)-catalyzed allylic oxidation of cyclic olefins
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New N,N-bidentate Schiff base ligands containing the 2-quinolyl moiety proved to be effective in conferring high reactivity and moderate to high enantioselectivity (up to 84% ee) to the copper(I)-catalyzed asymmetric allylic oxidation of various cylic ole
- Tan, Qitao,Hayashi, Masahiko
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supporting information; experimental part
p. 2639 - 2644
(2009/09/07)
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- Chiral boron-bridged bisoxazoline (borabox) ligands: Structures and reactivities of Pd and Cu complexes
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Anionic boron-bridged bisoxazolines (borabox ligands) have been synthesized and characterized in their protonated forms. The ligands are tuneable over a wide range, allowing either alkyl or aryl substituents at the oxazoline rings and the central bridging boron atom. The structural parameters of this new ligand type have been investigated by X-ray analyses of palladium and copper complexes. Electronic properties have been studied by 13C NMR spectroscopy and by DFT calculations on palladium allyl complexes and compared to those of analogous bisoxazoline (box) complexes. Borabox complexes are more electronrich at the metal center than their neutral box congeners, and as a consequence of the longer bonds between the bridging atom and the oxazoline rings, their bite angles are larger. Palladium(II) complexes bearing an unsubstituted allyl ligand and homoleptic copper(II) complexes each possess an almost flat chelate ring. NMR analysis of a (1,3-diphenylallyl)(borabox) palladium complex showed a 92:8 mixture of (syn,syn) and (anti,syn) allyl isomers, in contrast with a previously reported box analogue that existed exclusively in the (syn,syn) form. Comparison of the corresponding crystal structures revealed that the distance between the bisoxazoline and the allyl ligand in the borabox complex is shorter. In the copper-catalyzed allylic oxidation of cyclohexene and cyclopentene with tert-butyl perbenzoate, borabox ligands gave results similar - and in some cases superior - to those obtained with analogous box ligands.
- Koehler, Valentin,Mazet, Clement,Toussaint, Aurelie,Kulicke, Klaus,Haeussinger, Daniel,Neuburger, Markus,Schaffner, Silvia,Kaiser, Stefan,Pfaltz, Andreas
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experimental part
p. 8530 - 8539
(2009/09/29)
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- Azaarene cis-dihydrodiol-derived 2,2′-bipyridine ligands for asymmetric allylic oxidation and cyclopropanation
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Biphenyl dioxygenase-catalysed cis-dihydroxylation of 2-chloroquinoline, 2-chloro-3-methylquinoline and 2-chloro-6-phenylpyridine substrates yielded the corresponding enantiopure cis-dihydrodiols; enantiopure 2,2′-bipyridines, synthesised in four steps fr
- Boyd, Derek R.,Sharma, Narain D.,Sbircea, Lenuta,Murphy, Deirdre,Belhocine, Tayeb,Malone, John F.,James, Stuart L.,Allen, Christopher C. R.,Hamilton, John T. G.
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supporting information; experimental part
p. 5535 - 5537
(2009/04/12)
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- Copper complex catalyzed asymmetric monosulfonylation of meso-vic-diols
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Asymmetric desymmetrization of meso-vic-diols was performed by tosylation in the presence of copper(II) triflate and (R,R)-Ph-BOX as a catalyst. The method was successfully applied to asymmetric desymmetrization of cyclic and acyclic meso-vic-diols in hig
- Demizu, Yosuke,Matsumoto, Kazuya,Onomura, Osamu,Matsumura, Yoshihiro
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p. 7605 - 7609
(2008/03/14)
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- Preparation and application of bisoxazoline ligands with a chiral spirobiindane skeleton for asymmetric cyclopropanation and allylic oxidation
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A new type of bisoxazoline ligand 4 (abbreviated as SpiroBOX) containing a chiral spirobiindane scaffold were easily prepared in high yields from enantiomerically pure 1,1′-spirobiindane-7,7′-diol (SPINOL) with 1,1′-spirobiindane-7,7′-dicarboxylic acid as
- Liu, Bin,Zhu, Shou-Fei,Wang, Li-Xin,Zhou, Qi-Lin
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p. 634 - 641
(2007/10/03)
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- Enantioselective oxidation of olefins catalyzed by chiral copper bis(oxazolinyl)pyridine complexes: A reassessment
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Copper complexes of chiral tridentate pybox ligands synthesized using a modified procedure have been studied as catalysts for the enantioselective allylic oxidation of olefins. A variety of olefins have been used in this reaction. Using 5 mol% of a Cu(II)
- Ginotra, Sandeep K.,Singh, Vinod K.
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p. 3573 - 3581
(2007/10/03)
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- Studies on enantioselective allylic oxidation of olefins using peresters catalyzed by Cu(I)-complexes of chiral pybox ligands
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Enantioselective allylic oxidation of olefins with various peresters, using a catalytic amount of Cu(i)-pybox complex, can be tuned to achieve high asymmetric induction (up to 98% ee) by choosing a unique combination of a ligand and a perester at room temperature. The asymmetric induction in the reaction strongly depends on the nature of the substituents attached to the aryl ring of peresters. The presence of a gem-diphenyl group at C-5 and secondary or tertiary alkyl substituents at the chiral center (C-4) of the oxazoline rings is crucial for high enantioselectivity. A π-π stacking model has been proposed and discussed to explain the stereochemical outcome of the reaction. The Royal Society of Chemistry 2006.
- Ginotra, Sandeep K.,Singh, Vinod K.
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p. 4370 - 4374
(2008/09/19)
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- Synthesis of new chiral 2,2′-bipyridine ligands and their application in Copper-catalyzed asymmetric allylic oxidation and cyclopropanation
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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, β-pinene (10 → 1), 3-carene (14 → 3 and 5), 2-carene (28 → 4), α-pinene (43 → 6-8), and dehydropregnenolone acetate (48 → 9), respectively. Copper(I) complexes, derived from these ligands and (TfO)2Cu (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 ≤76% enantioselectivity and ~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.
- Malkov, Andrei V.,Pernazza, Daniele,Bell, Mark,Bella, Marco,Massa, Antonio,Teply, Filip,Meghani, Premji,Kocovsky, Pavel
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p. 4727 - 4742
(2007/10/03)
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- Catalytic enantioselective rearrangement of meso-epoxides mediated by chiral lithium amides in the presence of excess cross-linked polymer-bound lithium amides
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Insoluble polymer-bound achiral lithium dialkylamides were prepared from the corresponding cross-linked polymer-bound amines and butyllithium. The polymer-bound achiral reagent was applied to a catalytic enantioselective rearrangement of meso-epoxides as an in situ regenerating agent of a chiral lithium amide. The efficiency of the catalytic system was improved, and chiral allylic alcohol derivatives were obtained in high enantiomeric excesses by using excess polymer-bound reagents and a sub-stoichiometric amount of chiral lithium amide, prepared from (2S,3aS,7aS)-2-(pyrrolidin-1-ylmethyl)octahydroindole. The reaction was successfully applied in the synthesis of (1S,4R)-4-benzoylamino-2-cyclopentenol, a useful chiral synthetic intermediate for carbocyclic nucleosides, in 97% ee.
- Seki, Atsushi,Asami, Masatoshi
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p. 4655 - 4663
(2007/10/03)
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- Enantioselective allylic acyloxylation catalysed by copper-oxazoline complexes
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The oxidation of cyclic alkenes with peresters catalysed by copper complexes of bis-oxazolines, prepared from (1S,2R)-aminoindanol, affords acylated allylic alcohols in good yield and with good levels of enantiocontrol.
- Clark, J. Stephen,Tolhurst, Keith F.,Taylor, Mark,Swallow, Steven
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p. 1167 - 1169
(2007/10/03)
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- Enantioselective allylic oxidation of cycloalkenes by using Cu(II)-tris(oxazoline) complex as a catalyst
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Optically active copper(II)-tris(oxazoline) complex that was synthesized as a model compound of the active site of non-heme oxygenase, was found to catalyze allylic oxidation of cycloalkenes to give the corresponding 2-cycloalkenyl benzoates with moderate to excellent enantioselectivity (up to 93% ee) under die Kharash-Sosnovsky reaction conditions.
- Kawasaki, Ken-Ichi,Katsuki, Tsutomu
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p. 6337 - 6350
(2007/10/03)
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- Enantioselective Allylic Oxidation Catalyzed by Chiral Bisoxazoline-Copper complexes
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Copper(I) complexes prepared in situ from chiral bisoxazolines and Cu(II)OTf have been studied as catalysts for the allylic oxidation of cycloalkenes.Using 5 molpercent of catalyst and tert-butyl perbenzoate as oxidant, optically active 2-cycloalkenyl ben
- Gokhale, Abha S.,Minidis, Alexander B. E.,Pfaltz, Andreas
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p. 1831 - 1834
(2007/10/02)
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- Synthesis of chiral diferrocenyl dichalcogenides and their application to asymmetric nucleophilic ring opening of meso-epoxides
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Four novel optically active bis dichalcogenides , each of which possesses two axial and two central elements of chirality, have been prepared by lithiation of commercially available chiral (1-dimethylaminoethyl)ferrocenes, followed by treatment with elemental sulfur or tellurium and air oxidation, in 42-65percent isolated yields.The structure of the di-(S,R)-ferrocenyl disulfide has been fully characterized by X-ray crystallography.Ferrocenyl chalcogenide anions (Fc*E-) produced by reduction of the above (Fc*E)2 and the known (Fc*Se)2 with LiAlH4 in tetrahydrofuran are found to act as useful stereoselective nucleophiles for ring opening of meso-epoxides such as cyclohexene oxide, cyclopentene oxide, cyclooctene oxide and cis-stilbene oxide to give the corresponding ferrocenyl β-hydroxyalkyl chalcogenides in high yields with up to 71percent diastereomeric excess (de).Although the diastereoselectivity depends on the combination of chalcogen atom and meso-epoxide, it is generally higher with E = S and Se than with E = Te.Selenoxide elimination of (S,R)-2-(1-dimethylaminoethyl)ferrocenyl 2-hydroxycyclohexyl selenide (66percent de), obtained by the ring opening of cyclohexene oxide with (S,R)-(Fc*Se)2, gives (S)-cyclohex-2-enol with 60percent ee.The S-configuration suggests that the ring opening, by the nucleophilic attack of the chiral ferrocenyl chalcogenide anion on the epoxide carbon, mainly occurs via the least hindered transition state considering the interactions between the epoxide, the 1-dimethylaminoethyl moiety and the ferrocene.
- Nishibayashi, Yoshiaki,Singh, Jai Deo,Fukuzawa, Shin-ichi,Uemura, Sakae
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p. 2871 - 2876
(2007/10/02)
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- AN ASYMMETRIC TRANSFORMATION OF CYCLOHEXENE OXIDE TO (S)-2-CYCLOHEXEN-1-OL BY CHIRAL LITHIUM AMIDES
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(S)-2-Cyclohexen-1-ol is prepared in 92percent ee from cyclohexene oxide by using chiral lithium amides, prepared from butyllithium and (S)-2-(disubstituted aminomethyl)pyrrolidines, as bases.
- Asami, Masatoshi
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p. 829 - 832
(2007/10/02)
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