- Self-supported chiral polymeric MnIII salen complexes as highly active and recyclable catalysts for epoxidation of nonfunctionalized olefins
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Abstract A series of self-supported chiral polymeric MnIII N,N′-ethylenebis(salicylimine) (salen) complexes were synthesized through metalation of the corresponding salen ligands obtained by condensation of several bis/tris-aldehydes with (1R,2
- Roy, Tamal,Kureshy, Rukhsana I.,Khan, Noor-Ul H.,Abdi, Sayed H. R.,Bajaj, Hari C.
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- Electronic effects on enantioselectivity in epoxidation catalyzed by D 4-symmetric chiral porphyrins
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Asymmetric epoxidation of various aromatic olefins was examined with our D4-symmetric chiral porphyrin. The enantioselectivity was greatly improved upon when the substrates contained electron-deficient groups. Moreover, examination of electroni
- Nakagawa, Hiroshi,Sei, Yoshihisa,Yamaguchi, Kentaro,Nagano, Tetsuo,Higuchi, Tsunehiko
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- Whole-cell yeast-mediated preparation of (R)-2-chloro-1-(3-nitrophenyl) ethanol as a synthetic precursor for (R)-phenylephrine
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The incubated whole-cell biocatalyst of Pichia minuta JCM 3622 reduced 2-chloro-1-(3-nitrophenyl)ethanone to provide (R)-2-chloro-1-(3-nitrophenyl) ethanol with 99.2% ee in 87% isolated yield in the presence of Amberlite XAD-7 as a reservoir for the hydrophobic, crystalline and toxic substrate. The product was transformed to (R)-1-(3-hydroxyphenyl)-2-methylaminoethanol (phenylephrine, 1a), a selective α1-adrenergic receptor agonist, in 98.0% ee over five steps.
- Tokoshima, Daisuke,Hanaya, Kengo,Shoji, Mitsuru,Sugai, Takeshi
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- Exploration of chiral induction on epoxides in lipase-catalyzed epoxidation of alkenes using (2R,3S,4R,5S)-(-)-2,3:4,6-di-O-isopropylidiene-2-keto-l-gulonic acid monohydrate
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Epoxidation of alkenes by peracid, generated in situ from (2R,3S,4R,5S)-(-)-2,3:4,6-di-O-isopropylidiene-2-keto-l-gulonic acid monohydrate [(-)-DIKGA] and hydrogen peroxide by lipase catalysis induces chirality on the product epoxides with moderate to good enantioselectivity (35-71%). Alkoxy/aralkyloxy styrenes however did not undergo any epoxidation. (R)-(+)-4-Hydroxy styrene-7,8-oxide was formed and isolated with moderate enantiomeric excess (57%) but was found to have poor stability.
- Sarma, Kuladip,Goswami, Amrit,Goswami, Bhabesh C.
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experimental part
p. 1295 - 1300
(2009/10/17)
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- Dynamic kinetic resolution of racemic β-haloalcohols: Direct access to enantioenriched epoxides
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The direct chemo-enzymatic DKR of racemic β-haloalcohols is reported, yielding the corresponding optically active epoxides in a single step. The mutant haloalcohol dehalogenase HheC Cys153Ser Trp249Phe is used for the asymmetric ring closure, whereas racemization of the remaining enantiomer of the haloalcohol is achieved using the new iridacycle 3, one of the most effective racemization catalysts to date for β-haloalcohols. Copyright
- Haak, Robert M.,Berthiol, Florian,Jerphagnon, Thomas,Gayet, Arnaud J. A.,Tarabiono, Chiara,Postema, Christiaan P.,Ritleng, Vincent,Pfeffer, Michel,Janssen, Dick B.,Minnaard, Adriaan J.,Feringa, Ben L.,De Vries, Johannes G.
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supporting information; scheme or table
p. 13508 - 13509
(2009/02/06)
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- A novel method for the synthesis of chiral epoxides from styrene derivatives using chiral acids in presence of Pseudomonas lipase G6 [PSL G6] and hydrogen peroxide
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Chiral epoxidation of styrene and its derivatives was carried out using series of chiral acids and urea hydrogen peroxide (UHP) or aqueous hydrogen peroxide (50%) in two phases under the catalytic influence of immobilized Pseudomonas lipase G6 [PSL G6] at 25-55 °C. A moderate to good yield and enantioselectivities of chiral epoxides were obtained.
- Sarma, Kuladip,Bhati, Nishi,Borthakur, Naleen,Goswami, Amrit
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p. 8735 - 8741
(2008/02/09)
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- Chiral styrene oxides from α-haloacetophenones using NaBH4 and TarB-NO2, a chiral Lewis acid
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High enantioselectivities are obtained for the preparation of chiral styrene oxides through reduction of α-haloacetophenones using TarB-NO 2 reagent and the inexpensive and mild reducing agent NaBH 4. The epoxides are easily obtained in up to 95% ee through routine acid-base workup of the product alcohols. Either the (R) or (S) epoxide can be obtained by using the appropriate l- or d-tartaric acid starting material in the TarB-NO2 reagent.
- Cordes, David B.,Kwong, Tracey J.,Morgan, Kellie A.,Singaram, Bakthan
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p. 349 - 351
(2007/10/03)
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- Effective asymmetric epoxidation of styrenes by chiral dioxirane
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High enantioselectivity (80-92% enantiomeric excess (ee)) has been obtained for the epoxidation of various styrenes using an easily prepared ketone (4) catalyst.
- Goeddel, David,Shu, Lianhe,Yuan, Yi,Wong, O. Andrea,Wang, Bin,Shi, Yian
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p. 1715 - 1717
(2007/10/03)
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- Tryptamine-based human β3-adrenergic receptor agonists. Part 3: Improved oral bioavailability via modification of the sulfonamide moiety
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The continued SAR investigation of tryptamine-based human β3-adrenergic receptor (AR) agonists is reported. Prior efforts resulted in the identification of 2 as a potent β3-AR agonist. Further modification of the left side arylsulfonamide portion in 2 provided compounds with good cell permeability, which have potent agonistic activity for β3-AR. Cinnamylamine analog 16i exhibited an excellent agonistic profile in vitro and good oral bioavailability in rats.
- Sawa, Masaaki,Mizuno, Kazuhiro,Harada, Hiroshi,Tateishi, Hirotaka,Arai, Yukiyo,Suzuki, Shinya,Oue, Mayumi,Tsujiuchi, Hiroshi,Furutani, Yasuji,Kato, Shiro
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p. 1061 - 1064
(2007/10/03)
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- Direct catalytic synthesis of enantiopure 5-substituted oxazolidinones from racemic terminal epoxides
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(Chemical Equation Presented) A venerable scaffold for asymmetric synthesis and drug development, chiral 5-substituted oxazolidinones are obtained in almost enantiomerically pure form (up to 99.9% ee) starting from racemic terminal epoxides. The salient features of this process include the very simple and convenient experimental protocol and the employment of a readily accessible catalyst and inexpensive, easily handled starting materials. An enantioconvergent approach for the total conversion of racemic epoxide into a single stereoisomeric oxazolidinone is also described.
- Bartoli, Giuseppe,Bosco, Marcella,Carlone, Armando,Locatelli, Manuela,Melchiorre, Paolo,Sambri, Letizia
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p. 1983 - 1985
(2007/10/03)
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- Asymmetric catalytic synthesis of enantiopure N-protected 1,2-amino alcohols
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(Chemical Equation Presented) The asymmetric aminolytic kinetic resolution (AKR) of racemic terminal epoxides using carbamates as the nucleophile catalyzed by (salen)CoIII complex provides a practical and straightforward method for the synthesis of both aliphatic and aromatic N-Boc- or N-Cbz-protected 1,2-amino alcohols in almost enantiomerically pure form (ee ≥ 99%). The AKR uses an easily accessible catalyst and inexpensive starting materials, and the reactions are conveniently carried out at room temperature under an air atmosphere.
- Bartoli, Giuseppe,Bosco, Marcella,Carlone, Armando,Locatelli, Manuela,Melchiorre, Paolo,Sambri, Letizia
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p. 3973 - 3975
(2007/10/03)
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- Tryptamine-based human β3-adrenergic receptor agonists. Part 2: SAR of the methylene derivatives
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In an effort to reduce the cost of production, we conducted further optimization of tryptamine-based β3-adrenergic receptor (AR) agonists. Optimization of the left-hand side aryl moiety led to the identification of a series of potent β3/s
- Sawa, Masaaki,Tateishi, Hirotaka,Mizuno, Kazuhiro,Harada, Hiroshi,Oue, Mayumi,Tsujiuchi, Hiroshi,Furutani, Yasuji,Kato, Shiro
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p. 5963 - 5966
(2007/10/03)
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- A Unique Binaphthyl Strapped Iron-Porphyrin Catalyst for the Enantioselective Epoxidation of Terminal Olefins
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A new chiral binaphthyl-strapped iron-porphyrin 4b that exhibits unprecedented catalytic activity toward the enantioselective epoxidation of terminal olefins was synthesized. Typical enantiomeric excesses (ee) of 90% were measured with a maximum of 97% fo
- Rose, Eric,Ren, Qi-Zhi,Andrioletti, Bruno
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p. 224 - 230
(2007/10/03)
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- Highly selective hydrolytic kinetic resolution of terminal epoxides catalyzed by chiral (salen)CoIII complexes. Practical synthesis of enantioenriched terminal epoxides and 1,2-diols
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The hydrolytic kinetic resolution (HKR) of terminal epoxides catalyzed by chiral (salen)CoIII complex 1·OAc affords both recovered unreacted epoxide and 1,2-diol product in highly enantioenriched form. As such, the HKR provides general access to useful, highly enantioenriched chiral building blocks that are otherwise difficult to access, from inexpensive racemic materials. The reaction has several appealing features from a practical standpoint, including the use of H2O as a reactant and low loadings (0.2-2.0 mol %) of a recyclable, commercially available catalyst. In addition, the HKR displays extraordinary scope, as a wide assortment of sterically and electronically varied epoxides can be resolved to ≥ 99% ee. The corresponding 1,2-diols were produced in good-to-high enantiomeric excess using 0.45 equiv of H2O. Useful and general protocols are provided for the isolation of highly enantioenriched epoxides and diols, as well as for catalyst recovery and recycling. Selectivity factors (krel) were determined for the HKR reactions by measuring the product ee at ca. 20% conversion. In nearly all cases, krel values for the HKR exceed 50, and in several cases are well in excess of 200.
- Schaus, Scott E.,Brandes, Bridget D.,Larrow, Jay F.,Tokunaga, Makoto,Hansen, Karl B.,Gould, Alexandra E.,Furrow, Michael E.,Jacobsen, Eric N.
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p. 1307 - 1315
(2007/10/03)
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- Stereo- and enantioselective alkene epoxidations: A comparative study of D4- and D2-symmetric homochiral trans-dioxoruthenium(VI) porphyrins
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The mechanism of stoichiometric enantioselective alkene epoxidations by the D4- and D2-symmetric homochiral trans-dioxoruthenium(VI) porphyrins, [RuVI(D4-Por*)O2] (1) and [RuVI(D2-Por*)O2] (2a), in the presence of pyrazole (Hpz) was studied by UV/ Vis spectrophotometry and analysis of the organic products. The enantioselectivity of styrene oxidations is more susceptible to steric effects than to substituent electronic effects. Up to 72% ee was achieved for epoxidation of 3-substituted and cis-disubstituted styrenes by employing 1 as the oxidant, whereas entantioselectivities of only 20-40 % were obtained in the reactions with 2-substituted and trans-disubstituted styrenes. Complex 2a oxidized 2-substituted styrenes to their epoxides in up to 88% ee. Its reactions with transalkenes are more enantioselective (67 % ee) than with the cis-alkenes (40 % ee). Based on a two-dimensional NOESY NMR study, 2a was found to adopt a more open conformation in benzene than in dichloromethane, which explains the observed solvent-dependent enantioselectivity of its reactions with alkenes. The oxidation of aromatic alkenes by the chiral dioxoruthenium(VI) porphyrins proceeds through the ratelimiting formation of a benzylic radical intermediate; the observed enantioselectivity (eeobs) depends on both the facial selectivity of the first C-O bond formation step and the diastereoselectivity of the subsequent epoxide ring closure. To account for the observed facial selection, "side-on" and "top-on" approach transition state models are examined (see: B. D. Brandes, E. N. Jacobsen, Tetrahedron Lett. 1995, 36, 5123).
- Zhang, Rui,Yu, Wing-Yiu,Sun, Hong-Zhe,Liu, Wei-Sheng,Che, Chi-Ming
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p. 2495 - 2507
(2007/10/03)
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- 2,4-Thiazolidinediones as potent and selective human β3 agonists
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Methylsulfonamide substituted 2,4-thiazolidinedione 22c is a potent (EC50 = 0.01 μM, IA = 1.19) and selective (more than 110-fold over β1 and β2 agonist activity) β3 agonist. This compound has also been proven to be active and selective in an in vivo mode.
- Hu, Baihua,Ellingboe, John,Gunawan, Iwan,Han, Stella,Largis, Elwood,Li, Zenan,Malamas, Michael,Mulvey, Ruth,Oliphant, Alexander,Sum, Fuk-Wah,Tillett, Jeff,Wong, Victoria
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p. 757 - 760
(2007/10/03)
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- Mechanistic Investigation of the Oxidation of Aromatic Alkenes by Monooxoruthenium(IV). Asymmetric Alkene Epoxidation by Chiral Monooxoruthenium(IV) Complexes
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The oxoruthenium(IV) complexes [RuIV(terpy)(6,6′-Cl2-bpy)O](ClO4) 2 (1a; terpy = 2,2′:6′,2″-terpyridine; 6,6′-Cl2-bpy = 6,6′-dichloro-2,2′-bipyridine), [RuIV(terpy)(tmeda)O](ClO4)2 (lb; tmeda = N,N,N′,N′-tetramethylethylenediamine), tRuIV(Cn)(bpy)O](ClO4)2 (1c; Cn = l,4,7-trimethyl-l,4,7-triazacyclononane), and [RuIV(PPz*Xbpy)O](ClO4)2 (Id; PPz* = 2,6-bis[(4S,7A)-7,8,8-trimethyl4,5,6,7-tetrahydro-4,7-methanoindazol-2-yl] pyridine) are effective for the epoxidation of aromatic alkenes in acetonitrile at ambient conditions. Their reactions with c/s-alkenes such as cis-β-methylstyrene and cis-β-deuteriostyrene afford epoxides nonstereospecifically. The observation of the inverse secondary kinetic isotope effect for the β-d2-styrene oxidations [kH/kD -0.87 (1b), 0.86 (Id)], but not for α-deuteriostyrene (kH/kD = 0.98 for lb and Id), indicates that C-O bond formation is more advanced at the β-carbon atom than at the a carbon, i.e., a stepwise mechanism. The second-order rate constants (k2) for the styrene oxidations are weakly dependent on the E°(RuIV/III) values of the oxoruthenium(IV) complexes, and both electron-withdrawing and -donating para substituents mildly accelerate the oxidation reaction of styrene. These findings discount strongly the intermediaries of an alkene-derived cation radical and a carbocation. A linear free-energy relationship between the second-order rate constants for the para-substituted styrene oxidations and the total substituent effect (TE) parameters has been established: (TE) = +0.43 (R = 0.99) for 1b, +0.50 (R = 0.98) for 1c, and +0.37 (R = 0.99) for Id (Wu, Y.-D.; Wong, C.-L.; Chan, K. W.; Ji, G.-Z.; Jiang, X.-K. J. Org. Chem. 1996, 61, 746). This suggests that the oxidation of aromatic alkenes by oxoruthenium(IV) complexes should proceed via the rate-limiting formation of a benzylic radical intermediate. Oxidation of styrene and cis- and trans-β-methylstyrenes by the chiral oxoruthenium (IV) complex Id attains moderate enantioselectivities, in which the production of cis-epoxide is more enantioselective than the trans counterpart. The ligand dissymmetry of PPz* together with the bipyridine ligand create a "chiral pocket" around the RuIV=O moiety, leading to enantiofacial discrimination through nonbonding interaction. Because the acyclic benzylic radical intermediate would undergo cis-trans isomerization before the second C-O bond formation, the overall product enantioselectivity (% eeobs) cannot be determined exclusively by facial selectivity (eefacial) of the first irreversible C-O bond formation step. The extent of the isomerization, measured by the cis-trans-epoxide selectivity or diastereoselectivity of epoxide ring closure, is an important element in controlling the enantiomeric excess of the epoxides.
- Fung, Wai-Hong,Yu, Wing-Yiu,Che, Chi-Ming
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p. 7715 - 7726
(2007/10/03)
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- Asymmetric Epoxidation of Simple Olefins by Chiral Bitetralin-Linked "Twin-Coronet" Porphyrin Catalysts
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Catalytic and asymmetric epoxidation of styrenes and related aryl substituted olefins with the iron complexes of chiral bitetralin (Bitet)-linked "twin-coronet" porphyrins was performed with iodosylbenzene as an oxidant.Among two topological isomers of the catalyst, the eclipsed one (5b) showed higher enentioselectivity than the staggered (6b).With 5b, the resulting epoxides, except for the olefins bearing an electron-donating substituent, were obtained in good to excellent enantioselectivity (54-96percent ee), especially for the styrenes with electron-withdrawing substituent(s).Being different from other porphyrin-based chiral catalysts, the catalyst 5b is robust enough under the applied oxidation conditions to exhibit chiral epoxidation with the same ee and the same rate as those of the initial period of the reaction even after about 500 turnovers.The Bitet catalyst is superior in the epoxide enantioselectivity than the corresponding chiral binaphthalene (Binap)-linked catalyst (3b).In the reactions with the catalysts 3b and 5b, good correlation in epoxide ees was observed.Increase of the epoxide ee in the reaction with the Bitet catalyst was elucidated by the shape and size of the reaction cavities of the Bitet were tighter than those of the latter.The observed ees of the substituted styrene oxides showed good correlation with Σ?+ values of their substituent(s).In the reaction with the electron-deficient olefins, ?-?* interaction between the HOMO of the electron-rich Bitet auxiliary ring and the LUMO of the electron-deficient aryl ring of the substrate are pointed out as the key for the realization of high ees.Some nitrostyrenes, however, gave rather lower ees in spite of rather higher degree of their electron deficiency.This deviation was elucidated by the mismatching of their frontier orbitals.
- Naruta, Yoshinori,Ishihara, Nobuo,Tani, Fumito,Maruyama, Kazuhiro
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p. 158 - 166
(2007/10/02)
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- Synthesis of Chiral Bitetralin-strapped "Twin Coronet" Porphyrins. Catalytic and Asymmetric Epoxidation of Styrene Derivatives
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"Twin-coronet" porphyrins bearing optically active 1,1'-bitetrahydronaphthalene derivatives on the both faces of the porphyrin were prepared as enantioselective oxidation catalysts modeling on cytochrome P-450s.The eclipsed isomer of the corresponding iron(III) porphyrins catalyzed epoxidation of styrenes substituted with electron-withdrawing groups in high e.e. (61-89 percent) and high product selectivity.
- Naruta, Yoshinori,Ishihara, Nobuo,Tani, Fumito,Maruyama, Kazuhiro
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p. 1933 - 1936
(2007/10/02)
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- Synthesis of Chiral Square Planar Cobalt(III) Complexes and Catalytic Asymmetric Epoxidations with these Complexes
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The chiral square planar cobalt(III) complexes, Na4-(R)-HMBA-DMP)> (2), -2,4-dimethylpentan-3-one> and complexes with two or four chiral centres, Co2L> have been prepared and characterized by 1H NMR spectroscopy, solution magnetic properties, and X-ray crystallography.Asymmetric epoxidations of styrenes with these chiral cobalt(III) complexes and iodosylbenzene have been investigated.Various substituted styrenes were epoxidized with chemical yields of (25-86percent) and enantiomeric excess between 0 and 17percent.
- Ozaki, Shigeko,Mimura, Hisashi,Yasuhara, Naoko,Masui, Masaichiro,Yamagata, Yuriko,et al.
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p. 353 - 360
(2007/10/02)
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