- Asymmetric Epoxidation of Olefins Catalyzed by Substituted Aminobenzimidazole Manganese Complexes Derived from L-Proline
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A family of manganese complexes [Mn(Rpeb)(OTf)2] (peb=1-(1-ethyl-1H-benzo[d]imidazol-2-yl)-N-((1-((1-ethyl-1H-benzo[d]imidazol-2-yl)methyl) pyrrolidin-2-yl)methyl)-N-methylmethanamine)) derived from L-proline has been synthesized and characterized, where R refers to the group at the diamine backbone. X-ray crystallographic analyses indicate that all the manganese complexes [Mn(Rpeb)(OTf)2] exhibit cis-α topology. These types of complexes are shown to catalyze the asymmetric epoxidation of olefins employing H2O2 as a terminal oxidant with up to 96% ee. Obviously, the R group of the diamine backbone can influence the catalytic activity and enantioselectivity in the asymmetric epoxidation of olefins. In particular, Mn(i-Prpeb)(OTf)2 bearing an isopropyl arm, cannot catalyze the epoxidation reaction with H2O2 as the oxidant. However, when PhI(OAc)2 is used as the oxidant instead, all the manganese complexes including Mn(i-Prpeb)(OTf)2 can promote the epoxidation reactions efficiently. Taken together, these results indicate that isopropyl substitution on the Rpeb ligand inhibits the formation of active Mn(V)-oxo species in the H2O2/carboxylic acid system via an acid-assisted pathway.
- Tian, Jing,Lin, Jin,Zhang, Jisheng,Xia, Chungu,Sun, Wei
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supporting information
p. 593 - 600
(2021/11/16)
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- Effect of the Ligand Backbone on the Reactivity and Mechanistic Paradigm of Non-Heme Iron(IV)-Oxo during Olefin Epoxidation
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The oxygen atom transfer (OAT) reactivity of the non-heme [FeIV(2PyN2Q)(O)]2+ (2) containing the sterically bulky quinoline-pyridine pentadentate ligand (2PyN2Q) has been thoroughly studied with different olefins. The ferryl-oxo complex 2 shows excellent OAT reactivity during epoxidations. The steric encumbrance and electronic effect of the ligand influence the mechanistic shuttle between OAT pathway I and isomerization pathway II (during the reaction stereo pure olefins), resulting in a mixture of cis-trans epoxide products. In contrast, the sterically less hindered and electronically different [FeIV(N4Py)(O)]2+ (1) provides only cis-stilbene epoxide. A Hammett study suggests the role of dominant inductive electronic along with minor resonance effect during electron transfer from olefin to 2 in the rate-limiting step. Additionally, a computational study supports the involvement of stepwise pathways during olefin epoxidation. The ferryl bend due to the bulkier ligand incorporation leads to destabilization of both (Formula presented.) and (Formula presented.) orbitals, leading to a very small quintet–triplet gap and enhanced reactivity for 2 compared to 1. Thus, the present study unveils the role of steric and electronic effects of the ligand towards mechanistic modification during olefin epoxidation.
- Biswas, Jyoti Prasad,Ansari, Mursaleem,Paik, Aniruddha,Sasmal, Sheuli,Paul, Sabarni,Rana, Sujoy,Rajaraman, Gopalan,Maiti, Debabrata
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supporting information
p. 14030 - 14039
(2021/05/11)
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- Enantioselective, Stereoconvergent Resolution Copolymerization of Racemic cis-Internal Epoxides and Anhydrides
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Unprecedented enantioselective resolution copolymerization of racemic cis-internal epoxides and anhydrides was mediated by dinuclear aluminum complexes with multiple chirality, affording optically active polyesters with two contiguous stereogenic centers, and the unreacted substrates in good enantioselectivity. Unexpected stereoconvergence is observed in this resolution copolymerization, where the selectivity factor for the enantioselective formation of copolymer significantly exceeds the kinetic resolution coefficient based on the unreacted epoxide at various conversions. Catalytic activity and copolymer enantioselectivity are strongly influenced by the phenolate ortho-substituents of the ligand set, as well as the axial linker and its chirality. An enantiopure binaphthol-linked bimetallic AlIII complex allows stereoconvergent access to the stereoregular semi-crystalline polyesters and a concomitant kinetic resolution of the epoxide substrates.
- He, Guang-Hui,Ren, Bai-Hao,Chen, Shi-Yu,Liu, Ye,Lu, Xiao-Bing
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supporting information
p. 5994 - 6002
(2021/02/11)
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- A stand-alone cobalt bis(dicarbollide) photoredox catalyst epoxidates alkenes in water at extremely low catalyst load
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The cobalt bis(dicarbollide) complex, Na[3,3′-Co(η5-1,2-C2B9H11) (Na[1]), is an effective photoredox catalyst for the oxidation of alkenes to epoxides in water. Advantageous features of Na[1] include its lack of photoluminescence, high solubility and surfactant behavior in aqueous media, as well as the donor ability of the carborane ligand and high oxidizing power of the Co4+/3+ couple. These features differentiate it from the well-known and widely used photosensitizer tris (2,2′-bipyridine) ruthenium(ii) ([Ru(bpy)3]2+), which also participates in electron transfer through an outer sphere mechanism. A comparison of the catalytic performance of [Ru(bpy)3]2+ with Na[1] for alkene photo-oxidation is fully in favor of Na[1], as the former shows very low or null efficiency. With a catalyst loading of 0.1 mol% conversions between 65-97% have been obtained in short reaction times, 15 minutes, with moderate selectivity for the corresponding epoxide, due to the formation of side products as diols. But when the catalyst loading is reduced to 0.01 mol%, the selectivity for the corresponding epoxide increased considerably, being the only compound formed after 15 minutes of reaction (selectivity >99%). High TON values have been obtained (TON = 8500) for the epoxidation of aromatic and aliphatic alkenes in water. We have verified that Na[3,3′-Co(η5-1,2-C2B9H11)2] acts as a photocatalyst in both the epoxidation of alkenes and in their hydroxylation in aqueous medium with a higher rate for epoxidation than for hydroxylation. Preliminary photooxidation tests using methyl oleate as the substrate led to the selective epoxidation of the double bond. These results represent a promising starting point for the development of practical methods for the processing of unsaturated fatty acids, such as the valorisation of animal fat waste using this sustainable photoredox catalyst. This journal is
- Guerrero, Isabel,Romero, Isabel,Teixidor, Francesc,Vi?as, Clara
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supporting information
p. 10123 - 10131
(2021/12/27)
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- Biochar as supporting material for heterogeneous Mn(II) catalysts: Efficient olefins epoxidation with H2O2
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A novel type of hybrid catalytic materials [MnII-L?BC] has been developed using biochar (BC) as support material for covalent grafting of a MnII Schiff-base catalyst (MnII-L). The hybrid [MnII-L?BC] materials have been evaluated for an important catalytic process, epoxidation of olefins using H2O2 as oxidant. A number of different substrates were used, with cyclohexene achieving the highest yields. When compared to the non-grafted, homogeneous MnII-L, the hybrid catalysts [MnII-L?BC] show a significant enhancement of the catalytic efficiency i.e. as documented by the increase of Turnover Numbers (TONs) (826 for [MnII-L-SS550ox] and 822 for [MnII-L-SW550ox]) and Turnover Frequencies (TOFs) (551 h?1 for [MnII-L-SS550ox] and 411 h?1 for [MnII-L-SW550ox]). The interfacial catalytic mechanism and the role of the BC support have been analyzed by Raman and Electron Paramagnetic Resonance spectroscopies. Based on these data we discuss a mechanism where the high efficiency of the hybrid materials involves the biochar carbon layers acting as promoters of the substrate and products kinetics. To a broader context, this work exemplifies that biochar-based hybrid materials are potent for oxidative catalysis technologies.
- Borges Regitano, Jussara,Deligiannakis, Yiannis,Gemenetzi, Aikaterini,Louloudi, Maria,Mavrogiorgou, Alexandra,Pierri, Leticia
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- Process for isomerizing and converting (Z)-olefins to (E)-olefins
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The invention belongs to the technical field of metal catalytic synthesis, and discloses a method for isomerizing and converting (Z)-olefins into (E)-olefins. The (E)-olefins are prepared through a reaction at -30-80 DEG C for 0.5-48 h by using a combination of CoX2 and a PNP or PAO ligand as a catalyst in the presence of an activating reagent; and a molar ratio of the (Z)-olefins to the CoX2 to the PNP or PAO ligand to the activating reagent is 1:(0.00001-0.10):(0.00001-0.10):(0.00003-0.30). The catalyst used in the invention is the combination of the cheap metal cobalt salt and the simple and easily available ligand, no other toxic transition metal (such as ruthenium, rhodium and palladium) salt is added in the reaction, and the method also has the advantages of cheap and easily available raw material, good functional group tolerance, mild reaction conditions, simplicity in operation, and e atom economy of 100%.
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Paragraph 0136-0138
(2020/03/25)
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- A Ruthenium(II) Aqua Complex as Efficient Chemical and Photochemical Catalyst for Alkene and Alcohol Oxidation
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Different synthetic routes have been developed to obtain the aqua complex trans-[RuII(trpy)(pypz-H)(OH2)](PF6)2, Ru6. This complex, together with the chlorido intermediate complexes cis- and trans-[RuIICl(pypz-H)(trpy)]+, Ru5a and Ru5b, have been fully characterized by analytical, spectroscopic, and electrochemical methods. Furthermore, the trans-Ru5b complex has been characterized in the solid state through single-crystal X-ray diffraction analysis. The aqua complex Ru6 was tested as catalyst in the photooxidation of alcohols in water and in the chemical oxidation of alkenes, displaying a good performance with high selectivity values in both catalytic processes.
- Manrique, Ester,Fontrodona, Xavier,Rodríguez, Montserrat,Romero, Isabel
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p. 2124 - 2133
(2019/01/24)
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- Chiral Manganese Aminopyridine Complexes: the Versatile Catalysts of Chemo- and Stereoselective Oxidations with H2O2
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In the last decade, manganese(II) complexes with N-donor tetradentate aminopyridine ligands emerged as efficient catalysts of enantioselective epoxidation of olefins and direct selective oxidation of C?H groups in complex organic molecules, with environmentally benign oxidant hydrogen peroxide. In this personal account, we summarize the progress of these catalysts with regard to ligands design, structure-reactivity correlations, evaluation of the substrate scope, as well as mechanistic studies, shedding light on the nature of active sites and the mechanisms of selective oxygenations. Several practically promising catalytic syntheses with the aid of Mn aminopyridine catalysts are exemplified.
- Ottenbacher, Roman V.,Talsi, Evgenii P.,Bryliakov, Konstantin P.
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- Enhanced Turnover for the P450 119 Peroxygenase-Catalyzed Asymmetric Epoxidation of Styrenes by Random Mutagenesis
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A randomized library is constructed based on pET30a-CYP119-T214V plasmid. This library of random mutants of CYP119-T214V was screened by means of the reduced CO difference spectra and epoxidation of styrene. By using directed evolution, a new CYP119 quadr
- Wang, Li,Wei, Siping,Pan, Xianchao,Liu, Pingxian,Du, Xi,Zhang, Chun,Pu, Lin,Wang, Qin
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p. 2741 - 2749
(2018/02/28)
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- Asymmetric Epoxidation of Olefins with H2O2 Catalyzed by a Bioinspired Aminopyridine N4 Iron Complex
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An iron complex with a chiral aminopyridine N4 ligand bearing strong electron-donating and bulky morpholine groups on the ligand is synthesized and characterized. The iron complex serves to efficiently catalyze the asymmetric epoxidation of various olefins by employing aqueous hydrogen peroxide as the green oxidant, providing the corresponding epoxides in good to excellent yields and enantioselectivities (up to 93 % yield and 99.9 % ee). Owing to the introduction of morpholine functional groups on the ligand, the Fe-catalyzed reaction can proceed with a catalytic amount of the carboxylic acid partner (3 mol %).
- Wang, Wenfang,Sun, Qiangsheng,Xu, Daqian,Xia, Chungu,Sun, Wei
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p. 420 - 424
(2017/02/15)
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- Mn-Schiff base modified MCM-41, SBA-15 and CMK-3 NMs as single-site heterogeneous catalysts: Alkene epoxidation with H2O2 incorporation
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The development of new functional catalytic materials prepared via appropriate chemical modification of mesoporous silica SBA-15, MCM-41 or carbon nanomaterials CMK-3, are presented. Their synthesis has been carried out via two synthetic approaches: (a) a two steps procedure which includes grafting of the Schiff base ligand 1,3-bis[3-aza-3-(1-methyl-3-oxobut-1-enyl)-prop-3-en-1-yl]-2-(4-hydroxy-phenyl)-1,3-imidazolidine (L) onto the suppors and subsequent metalation of the so-formed hybrid material, and (b) an one step procedure which allows covalent grafting of the entire [MnII-Schiff base] catalyst onto the carbonaceous support. The resulting single-site heterogeneous catalysts were characterized and evaluated for alkene epoxidation with H2O2 in the presence of CH3COONH4 as additive. They are efficient and selective towards formation of epoxides. The highest TONs have been achieved by L@MCM-41-MnII and MnII-L@CMK-3. Moreover, MnII-L@CMK-3 is operative for a second use and kinetically very fast, demonstrating remarkably high TOFs 65-634 h-1 that is correlated to its practically zero porosity. Based on the present data, the textural features of the obtained catalysts are discussed in correlation with their catalytic performance.
- Mavrogiorgou,Baikousi,Costas,Mouzourakis,Deligiannakis,Karakassides,Louloudi
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- Ti-salalen mediated asymmetric epoxidation of olefins with H2O2: Effect of ligand on the catalytic performance, and insight into the oxidation mechanism
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The highly enantioselective epoxidation of several conjugated olefins with H2O2 in the presence of five chiral titanium(IV) salalen (dihydrosalen) complexes has been studied, with focus on the effects of substituents (electronic and
- Talsi, Evgenii P.,Rybalova, Tatyana V.,Bryliakov, Konstantin P.
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p. 131 - 137
(2016/06/09)
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- Engineering P450 Peroxygenase to Catalyze Highly Enantioselective Epoxidation of cis-β-Methylstyrenes
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P450 119 peroxygenase and its site-directed mutants are discovered to catalyze the enantioselective epoxidation of methyl-substituted styrenes. Two new site-directed P450 119 mutants, namely T213Y and T213M, which were designed to improve the enantioselectivity and activity for the epoxidation of styrene and its methyl substituted derivatives, were studied. The T213M mutant is found to be the first engineered P450 peroxygenase that shows highly enantioselective epoxidation of cis-β-methylstyrenes, with up to 91 % ee. Molecular modeling studies provide insights into the different catalytic activity of the T213M mutant and the T213Y mutant in the epoxidation of cis-β-methylstyrene. The results of the calculations also contribute to a better understanding of the substrate specificity and configuration control for the regio- and stereoselective peroxygenation catalyzed by the T213M mutant.
- Zhang, Chun,Liu, Ping-Xian,Huang, Lu-Yi,Wei, Si-Ping,Wang, Li,Yang, Sheng-Yong,Yu, Xiao-Qi,Pu, Lin,Wang, Qin
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p. 10969 - 10975
(2016/07/27)
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- Photocatalytic Asymmetric Epoxidation of Terminal Olefins Using Water as an Oxygen Source in the Presence of a Mononuclear Non-Heme Chiral Manganese Complex
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Photocatalytic enantioselective epoxidation of terminal olefins using a mononuclear non-heme chiral manganese catalyst, [(R,R-BQCN)MnII]2+, and water as an oxygen source yields epoxides with relatively high enantioselectivities (e.g., up to 60% enantiomeric excess). A synthetic mononuclear non-heme chiral Mn(IV)-oxo complex, [(R,R-BQCN)MnIV(O)]2+, affords similar enantioselectivities in the epoxidation of terminal olefins under stoichiometric reaction conditions. Mechanistic details of each individual step of the photoinduced catalysis, including formation of the Mn(IV)-oxo intermediate, are discussed on the basis of combined results of laser flash photolysis and other spectroscopic methods.
- Shen, Duyi,Saracini, Claudio,Lee, Yong-Min,Sun, Wei,Fukuzumi, Shunichi,Nam, Wonwoo
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supporting information
p. 15857 - 15860
(2016/12/23)
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- Proton-Promoted and Anion-Enhanced Epoxidation of Olefins by Hydrogen Peroxide in the Presence of Nonheme Manganese Catalysts
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We report a remarkable Br?nsted acid effect in the epoxidation of olefins by nonheme manganese catalysts and aqueous hydrogen peroxide. More specifically, a mononuclear nonheme manganese complex bearing a tetradentate N4 ligand, MnII(Dbp-MCP)(OTf)2 (Dbp-MCP = (1R,2R)-N,N′-dimethyl-N,N′-bis((R)-(3,5-di-tert-butyl-phenyl)-2-pyridinylmethyl)cyclohexane-1,2-diamine; OTf- = CF3SO3-), is a highly efficient catalyst in the epoxidation of olefins by aqueous H2O2 in the presence of H2SO4 (1-3 mol %). The yields of epoxide products as well as the chemo- and enantioselectivities increase dramatically in the presence of H2SO4; no formation of epoxides is observed in the absence of H2SO4. In addition, the product yields and enantioselectivities are dependent significantly on the manganese catalysts and Br?nsted acids. The catalytic epoxidation of olefins by other oxidants, such as peracids, alkyl hydroperoxides, and iodosylbenzene, is also affected by the presence of H2SO4; product yields and enantioselectivities are high and similar irrespective of the oxidants in the presence of H2SO4, suggesting that a common epoxidizing intermediate is generated in the reactions of [MnII(Dbp-MCP)]2+ and the oxidants. Mechanistic studies, performed with 18O-labeled water (H218O) and cumyl hydroperoxide, reveal that a high-valent manganese-oxo species is formed as an epoxidizing intermediate via O-O bond heterolysis of Mn-OOH(R) species. The role of H2SO4 is proposed to facilitate the formation of a high-valent Mn-oxo species and to increase the oxidizing power and enantioselectivity of the Mn-oxo oxidant in olefin epoxidation reactions. Density functional theory (DFT) calculations support experimental results such as the formation of a Mn(V)-oxo species as an epoxidizing intermediate.
- Miao, Chengxia,Wang, Bin,Wang, Yong,Xia, Chungu,Lee, Yong-Min,Nam, Wonwoo,Sun, Wei
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p. 936 - 943
(2016/02/05)
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- Reusable manganese compounds containing pyrazole-based ligands for olefin epoxidation reactions
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We describe the synthesis of new manganese(ii) and manganese(iii) complexes containing the bidentate ligands 2-(3-pyrazolyl)pyridine, pypz-H, and 3(5)-(2-hydroxyphenyl)pyrazole, HOphpz-H, with formula [MnX2(pypz-H)2] (X = Cl-, 1, CF3SO3-, 2, OAc-, 3 or NO3- (4)), [MnCl2(pypz-H)(H2O)2], 5, or [MnCl(Ophpz-H)2], 6. All the complexes have been characterized through analytical, spectroscopic and electrochemical techniques. Single X-ray structure analysis revealed a six-coordinated Mn(ii) ion in complexes 1-5, and a five-coordinated Mn(iii) ion in complex 6. Compound 5 is the first co-crystal of Mn(ii) containing Cl and H2O ligands together with bidentate nitrogen ligands. The catalytic activity of complexes 1-6 has been tested with regard to the epoxidation of styrene and, in the case of 1, 5 and 6, other alkenes have been epoxidized using peracetic acid as oxidant in different media, among which glycerol, a green solvent never used in epoxidation reactions using peracetic acid as oxidant. The catalysts show moderate to high conversions and selectivities towards the corresponding epoxides. For complexes 1, 5 and 6, a certain degree of cis → trans isomerization is observed in the case of cis-β-methylstyrene. These observations have been explained through computational calculations. The reutilization of catalysts 1 and 6 for the epoxidation of alkenes has been evaluated in [bmim]:acetonitrile mixture (bmim = 1-butyl-3-methylimidazolium), allowing the effective recyclability of the catalytic system and keeping high conversion and selectivity values up to 12 successive runs, in all cases.
- Manrique, Ester,Poater, Albert,Fontrodona, Xavier,Solà, Miquel,Rodríguez, Montserrat,Romero, Isabel
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p. 17529 - 17543
(2015/10/19)
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- Synergistic interplay of a non-heme iron catalyst and amino acid coligands in H2O2 activation for asymmetric epoxidation of α-alkyl-substituted styrenes
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Highly enantioselective epoxidation of α-substituted styrenes with aqueous H2O2 is described by using a chiral iron complex as the catalyst and N-protected amino acids (AAs) as coligands. The amino acids synergistically cooperate with the iron center in promoting an efficient activation of H2O2 to catalyze epoxidation of this challenging class of substrates with good yields and stereoselectivities (up to 97% ee) in short reaction times.
- Cuss, Olaf,Ribas, Xavi,Lloret-Fillol, Julio,Costas, Miquel
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supporting information
p. 2729 - 2733
(2015/03/04)
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- A method for producing an optically active epoxy compound
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PROBLEM TO BE SOLVED: To provide a new method for producing an optically active epoxy compound.SOLUTION: The method includes a step of reacting an oxidizing agent with an unsaturated compound that has a double bond within the molecule in the presence of a
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-
Paragraph 0098-0100; 0102-0107
(2019/01/05)
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- Appended corrole manganese complexes: Catalysis and axial-ligand effect
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A series of N-base appended corroles and their manganese complexes were synthesized and their binding constants with three different nitrogenous ligands, triethylamine, N-methylimidazole and pyridine, were evaluated by spectroscopy. Kinetic studies indica
- Ng, Nga-Chun,Mahmood, Mian Hr,Liu, Hai-Yang,Yam, Fei,Yeung, Lam-Lung,Chang, Chi-K.
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supporting information
p. 571 - 574
(2014/05/06)
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- Dinuclear ruthenium complexes containing the Hpbl ligand: Synthesis, characterization, linkage isomerism, and epoxidation catalysis
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Three dinucleating Ru-Cl complexes containing the hexadentate dinucleating ligand [1,1′-(4-methyl-1H-pyrazole-3,5-diyl)bis(1-(pyridin-2-yl)ethanol)] (Hpbl) and the meridional 2,2′:6′,2″-terpyridine ligand (trpy) have been prepared and isolated. These comp
- Francs, Laia,Gonzlez-Gil, Rosa Mara,Moyano, Daniel,Benet-Buchholz, Jordi,Garca-Antn, Jordi,Escriche, Llus,Llobet, Antoni,Sala, Xavier
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p. 10394 - 10402
(2015/02/19)
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- Synthesis, characterization, magnetic and catalytic properties of a ladder-shaped MnII coordination polymer
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[Mn(LH)(H2O)]n {1, where LH2- is the dianion of N-(4-carboxybenzyl)iminodiacetic acid} has been synthesized and its crystal structure has been determined. The crystal of 1 is built from 1D polymeric ladder-shaped chains that extend to a 3D supramolecular architecture through H-bonds. The compound was characterized with spectroscopic and physicochemical techniques. Variable-temperature magnetic data suggest that there are weak antiferromagnetic interactions. Compound 1 has been evaluated as a heterogeneous oxidation catalyst. It catalyzes alkene epoxidation selectively in relatively high yields. Copyright
- Lymperopoulou, Smaragda,Papastergiou, Maria,Louloudi, Maria,Raptopoulou, Catherine P.,Psycharis, Vassilis,Milios, Constantinos J.,Plakatouras, John C.
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p. 3638 - 3644
(2014/08/18)
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- Synthesis, Characterization, Magnetic and Catalytic Properties of a Ladder-Shaped MnII Coordination Polymer
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[Mn(LH)(H2O)]n {1, where LH2- is the dianion of N-(4-carboxybenzyl)iminodiacetic acid} has been synthesized and its crystal structure has been determined. The crystal of 1 is built from 1D polymeric ladder-shaped chains that extend to a 3D supramolecular architecture through H-bonds. The compound was characterized with spectroscopic and physicochemical techniques. Variable-temperature magnetic data suggest that there are weak antiferromagnetic interactions. Compound 1 has been evaluated as a heterogeneous oxidation catalyst. It catalyzes alkene epoxidation selectively in relatively high yields.
- Lymperopoulou, Smaragda,Papastergiou, Maria,Louloudi, Maria,Raptopoulou, Catherine P.,Psycharis, Vassilis,Milios, Constantinos J.,Plakatouras, John C.
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p. 3638 - 3644
(2015/04/27)
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- Manganese complexes with non-porphyrin N4 ligands as recyclable catalyst for the asymmetric epoxidation of olefins
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New chiral manganese complexes of N4 ligands derived from 2-acetylpyridine were prepared and used as catalysts in the enantioselective epoxidation of olefins, using H2O2 as an oxidant to give epoxides, with excellent conversions (up to 99%) and enantiomeric excess (up to 88%) within 1 h at 0°C. A detailed mechanistic study was undertaken based on the information obtained by single crystal X-ray, optical rotation, UV-Vis, CD spectra and kinetic studies, and revealed that the reaction is first order with respect to the concentration of catalyst and oxidant and independent of substrate concentration. The complex (0.1 mol%) was successfully subjected to recyclability experiments over 3 cycles in the epoxidation of styrene with H2O2 as an oxidant and acetic acid as an additive at 0°C with retention of performance.
- Maity, Nabin Ch.,Kumar Bera, Prasanta,Ghosh, Debashis,Abdi, Sayed H. R.,Kureshy, Rukhsana I.,Khan, Noor-Ul H.,Bajaj, Hari C.,Suresh
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p. 208 - 217
(2014/01/06)
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- Asymmetric epoxidation of olefins with hydrogen peroxide by an in situ-formed manganese complex
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Asymmetric epoxidation of a variety of cis, trans, terminal, and trisubstituted olefins in excellent yields (up to 94%) and enantioselectivities (>99% ee) by an in situ-formed manganese complex using H2O 2 has been developed. A relationship between the hydrophobicity of the catalyst imposed by ligand and the catalytic activity has been observed. The influence of the amount and identity of the acid additive was examined, and improved enantioselectivities were achieved through the use of a catalytic amount of a carboxylic acid additive.
- Dai, Wen,Shang, Sensen,Chen, Bo,Li, Guosong,Wang, Lianyue,Ren, Lanhui,Gao, Shuang
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p. 6688 - 6694
(2014/08/05)
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- A mononuclear manganese complex of a tetradentate nitrogen ligand - Synthesis, characterizations, and application in the asymmetric epoxidation of olefins
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A new chiral manganese complex (C1) bearing a tetradentate nitrogen ligand containing chiral bipyrrolidine and benzimidazole moieties was prepared. The structure of C1 was confirmed by ESI-MS and crystallography. This manganese complex is an active catalyst for the asymmetric epoxidation of various olefins with excellent conversion (up to 99%) and high enantiomeric excess (up to 96%ee) with hydrogen peroxide as the oxidant in the presence of 2-ethylhexanoic acid or acetic acid. Compared with previous structurally similar manganese complexes with different diamine backbones (C2, cyclohexanediamine; C3, diamine from L-proline), C1 showed improved asymmetric induction, especially for simple olefins such as styrene derivatives and substituted chromene. The possible reasons for the improvement of the ee values are discussed in the text on the basis of the crystal structures of the manganese complexes.
- Shen, Duyi,Miao, Chengxia,Wang, Shoufeng,Xia, Chungu,Sun, Wei
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supporting information
p. 5777 - 5782
(2015/02/19)
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- Novel chiral (salen)Mn(iii) complexes containing a calix[4]arene unit in 1,3-alternate conformation as catalysts for enantioselective epoxidation reactions of (Z)-aryl alkenes
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Two new chiral calix[4]arene-salen ligands 1a,b, based on calix[4]arene platforms in 1,3-alternate conformation, have been prepared by a new general synthetic pathway. Their Mn(iii) complexes, 3a,b, have shown fairly good efficiency in the asymmetric epoxidation of styrene and substituted styrenes, whereas excellent catalytic activity and selectivity were observed with rigid bicyclic alkenes, namely 1,2-dihydro-naphthalene and substituted 2,2′-dimethyl-chromene. The higher catalytic properties of 3a may be ascribed to the more rigid and inherently chiral structure as proved by molecular modelling, NMR spectroscopy and X-ray data of the similarly structured UO2 complexes 2a,b.
- Bonaccorso, Carmela,Brancatelli, Giovanna,Ballistreri, Francesco P.,Geremia, Silvano,Pappalardo, Andrea,Tomaselli, Gaetano A.,Toscano, Rosa M.,Sciotto, Domenico
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p. 2183 - 2193
(2014/01/17)
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- Organic carbonates as solvents in macrocyclic Mn(III) salen catalyzed asymmetric epoxidation of non-functionalized olefins
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Organic carbonates, e.g., dimethyl carbonate and propylene carbonate were used as reaction media in enantioselective epoxidation of non-functionalized alkenes by using a series of chiral macrocyclic Mn(III) salen complexes (5 mol%) as catalyst with pyridi
- Maity, Nabin Ch.,Rao, Ganga V.S.,Prathap,Abdi, Sayed H.R.,Kureshy, Rukhsana I.,Khan, Noor-Ul H.,Bajaj, Hari C.
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p. 380 - 389
(2013/02/22)
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- Oxygen-atom transfer from iodosylarene adducts of a manganese(IV) salen complex: Effect of arenes and anions on I(III) of the coordinated iodosylarene
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This paper reports preparation, characterization, and reactivity of iodosylarene adducts of a manganese(IV) salen complex. In order to systematically investigate steric and electronic factors that control reactivity and selectivity, we prepared iodosylare
- Wang, Chunlan,Kurahashi, Takuya,Inomata, Kensuke,Hada, Masahiko,Fujii, Hiroshi
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p. 9557 - 9566
(2013/09/12)
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- Titanium salalen catalysts based on cis-1,2-diaminocyclohexane: Enantioselective epoxidation of terminal non-conjugated olefins with H 2O2
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Terminal, non-conjugated olefins, such as 1-octene, are difficult to epoxidize asymmetrically. Ti salalen complexes based on cis-1,2- diaminocyclohexane catalyze this demanding reaction giving high yields and enantioselectivities (up to 95 % ee), with H2O2 as the oxidant. The X-ray structures of the μ-oxo and peroxo complexes shed light on the coordination behavior of this novel class of ligands.
- Berkessel, Albrecht,Guenther, Thomas,Wang, Qifang,Neudoerfl, Joerg-M.
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supporting information
p. 8467 - 8471
(2013/09/02)
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- Highly stereoselective epoxidation with H2O2 catalyzed by electron-rich aminopyridine manganese catalysts
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Fast, efficient, and highly stereoselective epoxidation with H 2O2 is reached by manganese coordination complexes with e-rich aminopyridine tetradentate ligands. It is shown that the electronic properties of these catalysts vary systematically with the stereoselectivity of the O-atom transfer event and exert fine control over the activation of hydrogen peroxide, reducing the amount of carboxylic acid co-catalyst necessary for efficient operation.
- Cusso, Olaf,Garcia-Bosch, Isaac,Font, David,Ribas, Xavi,Lloret-Fillol, Julio,Costas, Miquel
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supporting information
p. 6158 - 6161
(2014/01/17)
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- The elpaN-salen series: Multifunctional ligands based on D-glucose for the Mn(III)-catalyzed enantioselective epoxidation of styrenes
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It is described the simple design of a series of N,N′,O,O′- chiral ligands (elpaN-salen-H2), which represent a subset of the elpaN-type library of ligands based on β-1,2-D-glucodiamine. The corresponding Mn(III) complexes were examined in the asymmetric epoxidation of styrenes with satisfactory results, e.g. cis-β-methylstyrene was functionalised in ees up to 88%.
- Ruffo, Francesco,Bismuto, Alessandro,Carpentieri, Andrea,Cucciolito, Maria E.,Lega, Matteo,Tuzi, Angela
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p. 288 - 294
(2013/10/22)
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- Structure and reactivity of an iodosylarene adduct of a manganese(IV)-salen complex
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O transfer: The X-ray crystal structure of an iodosylarene adduct of a manganese(IV)-salen complex shows bis-iodosylarene coordination with a stepped conformation of the salen ligand. Spectroscopic characterization suggests that the complex maintains the
- Wang, Chunlan,Kurahashi, Takuya,Fujii, Hiroshi
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supporting information; experimental part
p. 7809 - 7811
(2012/09/21)
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- Stereoselective epoxidation of alkenes with hydrogen peroxide using a bipyrrolidine-based family of manganese complexes
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Novel manganese complexes containing N4-tetradentate ligands derived from chiral bipyrrolidinediamines catalyze the stereoselective epoxidation of a wide array of alkenes using low catalyst loadings (0.1 mol%) and hydrogen peroxide (1.2 equiv.) as terminal oxidant. This family of catalysts affords good to excellent yields (80-100%) and moderate to good ees (40-73%) in short reaction times (30 min) making efficient use of hydrogen peroxide.
- Garcia-Bosch, Isaac,Gomez, Laura,Polo, Alfonso,Ribas, Xavi,Costas, Miquel
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supporting information; experimental part
p. 65 - 70
(2012/03/27)
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- Stereoselective benzylic hydroxylation of alkylbenzenes and epoxidation of styrene derivatives catalyzed by the peroxygenase of Agrocybe aegerita
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Here we report on the stereoselective benzylic hydroxylation and C1-C2 epoxidation of alkylbenzenes and styrene derivatives, respectively, by a heme-thiolate peroxygenase (EC 1.11.2.1) from the fungus Agrocybe aegerita. Benzylic hydroxylation led exclusively to the (R)-1-phenylalkanols. For (R)-1-phenylethanol, (R)-1-phenylpropanol and (R)-1-tetralol, the ee reached >99%. For longer chain lengths, the enantiomeric excesses (ee) and total turnover numbers (TTN) decreased while the number of by-products, e.g. 1-phenylketones, increased. Epoxidation of straight chain and cyclic styrene derivatives gave a heterogeneous picture and resulted in moderate to excellent ee values and TTN: e.g., in the case of (1R,2S)-cis-β-methylstyrene oxide formation, an ee >99% and a TTN of 110000 was achieved. Hydroxylation and epoxidation were true peroxygenations, which was demonstrated by the incorporation of 18O from H218O2 into the products. The use of fed-batch devices and varying feeding strategies for the substrate and co-substrate turned out to be a suitable approach to optimize peroxygenase catalysis.
- Kluge, Martin,Ullrich, Rene,Scheibner, Katrin,Hofrichter, Martin
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supporting information; experimental part
p. 440 - 446
(2012/04/10)
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- Immobilized dimeric chiral Mn(III) salen complex on short channel ordered mesoporous silica as an effective catalyst for the epoxidation of non-functionalized alkenes
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Chiral dimeric Mn(III) salen complex with 1R, 2R-(-)-diaminocyclohexane collar was immobilized on short channel large pore sized silica through a long linker of {(CH2)3-NH-melamine-piperazine} to investigate its performance in enanti
- Roy, Tamal,Kureshy, Rukhsana I.,Khan, Noor-Ul H.,Abdi, Sayed H.R.,Sadhukhan, Arghya,Bajaj, Hari C.
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experimental part
p. 6314 - 6322
(2012/08/28)
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- Biaryl-bridged salalen ligands and their application in titanium-catalyzed asymmetric epoxidation of olefins with aqueous H2O2
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A series of biaryl-bridged salalen ligands together with their titanium complexes have been designed and synthesized. The Ti complexes could serve as highly efficient catalysts for the asymmetric epoxidation of a wide range of olefins, giving the corresponding epoxides with high ee values. A biaryl-bridged salalen titanium complex was developed and used in the enantioselective epoxidation of a range of olefins with aqueous hydrogen peroxide as the oxidant. Notably, the intramolecular dinuclear Ti catalyst possessing a biaryl bridge is highly efficient for the reaction, especially using terminal aromatic olefins as substrates.
- Xiong, Donglu,Hu, Xiaoxue,Wang, Shoufeng,Miao, Cheng-Xia,Xia, Chungu,Sun, Wei
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experimental part
p. 4289 - 4292
(2011/09/15)
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- Asymmetric counteranion-directed transition-metal catalysis: Enantioselective epoxidation of alkenes with Manganese(III) salen phosphate complexes
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(Figure Presented) Figure Presentation Paired up: A highly active and enantioselective ion-pair epoxidation catalyst, consisting of an achiral Mn |||-salen complex and a chiral phosphate counteranion, mediates the epoxidization of a wide range of alkenes with high yields and enantioselectivities (see scheme). The unique role of the counteranion is to stabilize an enantiomorphic conformation of the cationic Mn catalyst.
- Liao, Saihu,List, Benjamin
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supporting information; experimental part
p. 628 - 631
(2010/04/06)
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- A diacetate ketone-catalyzed asymmetric epoxidation of olefins
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(Chemical Equation Presented) A fructose-derived diacetate ketone has been shown to be an effective catalyst for asymmetric epoxidation. High ee values have been obtained for a variety of trans and trisubstituted olefins including electron-deficient α,β-unsaturated esters as well as certain cis olefins.
- Wang, Bin,Wu, Xin-Yan,Wong, O. Andrea,Nettles, Brian,Zhao, Mei-Xin,Chen, Dajun,Shi, Yian
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experimental part
p. 3986 - 3989
(2009/09/30)
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- Asymmetric epoxidation catalyzed by α,α-dimethylmorpholinone ketone. Methyl group effect on spiro and planar transition states
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(Chemical Equation Presented) Asymmetric epoxidation of olefins by using an α,α-dimethylmorpholinone-containing chiral ketone catalyst (4) has been investigated. This ketone, which has the combined features of several previously studied catalysts, is an effective catalyst for trans- and trisubstituted olefins, and up to 97% ee has been achieved. The R, R-dimethyl group has significant impact on spiro and planar transition states.
- Wong, O. Andrea,Wang, Bin,Zhao, Mei-Xin,Shi, Yian
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supporting information; experimental part
p. 6335 - 6338
(2009/12/26)
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- Accessible sugars as asymmetric olefin epoxidation organocatalysts: Glucosaminide ketones in the synthesis of terminal epoxides
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A systematically varied series of conformationally restricted ketones, readily prepared from N-acetyl-d-glucosamine, were tested against representative olefins as asymmetric epoxidation catalysts showing useful selectivities against terminal olefins and, in particular, typically difficult 2,2-disubstituted terminal olefins.
- Boutureira, Omar,McGouran, Joanna F.,Stafford, Robert L.,Emmerson, Daniel P. G.,Davis, Benjamin G.
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supporting information; experimental part
p. 4285 - 4288
(2009/12/05)
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- A chiral iron-sexipyridine complex as a catalyst for alkene epoxidation with hydrogen peroxide
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A chiral iron-sexipyridine complex-hydrogen peroxide mixture is a highly efficient catalytic system for styrene epoxidation with excellent reactivity (3 min, 95% yield) and chemoselectivity (98%). The Royal Society of Chemistry.
- Yeung, Ho-Lun,Sham, Kiu-Chor,Tsang, Chui-Shan,Lau, Tai-Chu,Kwong, Hoi-Lun
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scheme or table
p. 3801 - 3803
(2009/02/08)
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- Enantioselective epoxidation of β-methylstyrene catalyzed by immobilized Mn(salen) catalysts in different mesoporous silica supports
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Mesoporous silica-supported chiral Mn(salen) catalysts were prepared and evaluated in the heterogeneous asymmetric epoxidation of β-methylstyrene with NaClO as an oxidant. Homogeneous and immobilized Mn(salen) catalysts exhibit similar cis/trans ratios an
- Zhang, Haidong,Wang, Yi Meng,Zhang, Lei,Gerritsen, Gijsbert,Abbenhuis, Hendrikus C.L.,van Santen, Rutger A.,Li, Can
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p. 226 - 236
(2008/09/21)
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- Asymmetric epoxidation of 1,1-disubstituted terminal olefins by chiral dioxirane via a planar-like transition state
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(Chemical Equation Presented) Various 1,1-disubstituted terminal olefins have been investigated for asymmetric epoxidation using chiral ketone catalysts. Up to 88% ee has been achieved with a lactam ketone, and a planar transition state is likely to be a
- Wang, Bin,Wong, O. Andrea,Zhao, Mei-Xin,Shi, Yian
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supporting information; experimental part
p. 9539 - 9543
(2009/04/07)
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- PROCESS FOR PRODUCING OPTICALLY ACTIVE EPOXY COMPOUND, COMPLEX FOR USE IN THE PROCESS, AND PROCESS FOR PRODUCING THE SAME
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There is provided a method for industrially producing optically active epoxy compounds by asymmetrically epoxidizing prochiral unsaturated compounds with an oxidant using as a catalyst a single substance or a di-μ-oxo dimer derived therefrom represented by any of the following formulae (I), (I'), (II), (II'), (III), (III'), (IV), and (IV'): [wherein R1s are independently an alkyl group or an aryl group; R2s are independently an alkyl group or an aryl group; R3s are independently an alkyl group or an aryl group, provided that two R3s may be bonded with each other to form a ring; R4s are independently a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a nitro group, or a cyano group; M is TiY2 (Y is Cl, alkoxide, or a μ-oxo ligand)].
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Page/Page column 23-24
(2010/11/28)
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- Enantioselective epoxidation of non-functionalized alkenes using carbohydrate based salen-Mn(III) complexes
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Three new salen ligands with carbohydrate moieties were prepared from a salicylaldehyde derivative obtained by reaction of 1,2:5,6-di-O-isopropylidene-α-d-glucofuranose with 3-tert-butyl-5-(chloro-methyl)-2-hydroxybenzaldehyde. These ligands were coordinated with Mn(III) to give three chiral salen-Mn(III) complexes. The complexes were characterized and employed in the asymmetric epoxidation of unfunctionalized alkenes. Catalytic results showed that although there are no chiral groups on the diimine bridge, these complexes had some enantioselectivity, which indicates the carbohydrate moiety has an asymmetric inducing effect in the epoxidation reaction.
- Zhao, Shanshan,Zhao, Jiquan,Zhao, Dongmin
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p. 254 - 258
(2007/10/03)
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- Development and application of versatile bis-hydroxamic acids for catalytic asymmetric oxidation
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In this article, we describe the development and preliminary results of our new designed C2-symmetric bis-hydroxamic acid (BHA) ligands and the application of the new ligands for vanadium-catalyzed asymmetric epoxidation of allylic alcohols as well as homoallylic alcohols. From this success we demonstrate the versatile nature of BHA in the molybdenum catalyzed asymmetric oxidation of unfunctionalized olefins and sulfides.
- Barlan, Allan U.,Zhang, Wei,Yamamoto, Hisashi
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p. 6075 - 6087
(2008/02/03)
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- An N-aryl-substituted oxazolidinone-containing ketone-catalyzed asymmetric epoxidation with hydrogen peroxide as the primary oxidant
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(Chemical Equation Presented) Asymmetric epoxidation of various olefins with an N-aryl-substituted oxazolidinone-containing ketone as catalyst and hydrogen peroxide as the primary oxidant has been investigated, and up to 96% ee was obtained.
- Burke, Christopher P.,Shu, Lianhe,Shi, Yian
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p. 6320 - 6323
(2008/02/09)
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- Trimanganese complexes bearing bidentate nitrogen ligands as a highly efficient catalyst precursor in the epoxidation of alkenes
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A series of trinuclear manganese complexes coordinated with neutral bidentate nitrogen ligands, [Mn3L2-(OAc)6], were prepared from manganese acetate and the corresponding ligands. Using peracetic acid as the oxidant, the air- and moisture-stable manganese clusters exhibited excellent catalytic activity and selectivity in the epoxidation of olefins under mild conditions. The highest activity was observed with a trinuclear complex containing a 2-pyridylimino ligand, [Mn3(ppei) 2(OAc)6] (ppei = 2-pyridinal-1-phenylethylimine). With this system, the substrate scope was extremely wide to include terminal and electron-deficient double bonds of both aliphatic and aromatic alkenes. The high activity was undiminished under the reaction conditions even directly using a mixture of the pyridylimino ligands and manganese acetates, making this process more convenient. It was also observed that analogous trinuclear complexes, such as [Mn3(bipy)2(OAc)6] and [Mn 3(phen)2(OAc)6], displayed excellent activities. While radical intermediacy was inferred from the product distribution, kinetic data revealed that the epoxidation is roughly first-order in manganese cluster precursor and oxidant, respectively, and zero-order in olefin. These results led us to propose that the trinuclear complexes [Mn 3L2(OAc)6] serve as catalyst precursors that dissociate into monomeric species with the formulation of [MnL 2(OAc)2] under the reaction conditions.
- Kang, Byungman,Kim, Min,Lee, Junseong,Do, Youngkyu,Chang, Sukbok
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p. 6721 - 6727
(2007/10/03)
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- Oxidation chemistry of poly(ethylene glycol)-supported carbonylruthenium(ii) and dioxoruthenium(vi) meso-tetrakis(pentafluorophenyl) porphyrin
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[Ru11(F20-tpp)(CO)] (1, F20-tpp = meso-tetrakis(pentafluorophenyl)porphyrinato dianion) was covalently attached to poly(ethylene glycol) (PEG) through the reaction of 1 with PEG and sodium hydride in DMF. The water-soluble PEG-supported ruthenium porphyrin (PEG-1) is an efficient catalyst for 2,6-Cl2pyNO oxidation and PhI=NTs aziridination/amidation of hydrocarbons, and intramolecular amidation of sulfamate esters with PhI (OAc)2. Oxidation of PEG-1 by m-CPBA in CH2C12, dioxane, or water afforded a water-soluble PEG-supported dioxoruthenium(VI) porphyrin (PEG-2), which could react with hydrocarbons to give oxidation products in up to 80 % yield. The behavior of the two PEG-supported ruthenium porphyrin complexes in water was probed by NMR spectroscopy and dynamic light-scattering measurements. PEG-2 is remarkably stable to water. The secondorder rate constants (k2) for the oxidation of styrene and ethylbenzene by PEG-2 in dioxane-water increase with water content, and the k2 values at a water content of 70% or 80% are up to 188 times that obtained in ClCH2CH2Cl.
- Zhang, Jun-Long,Huang, Jie-Sheng,Che, Chi-Ming
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p. 3020 - 3031
(2008/02/04)
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- Asymmetric epoxidation of 6-cyano-2,2-dimethylchromene on Mn(salen) catalyst immobilized in mesoporous materials
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This article reports our recent work on the heterogeneous asymmetric epoxidation catalyzed by chiral Mn(salen) catalyst axially immobilized via phenoxyl groups and organic sulfonic groups. The asymmetric epoxidation of 6-cyano-2,2-dimethylchromene was especially presented in detail. The factors that affected the asymmetric induction, such as the nanopores and the external surface, the linkage length, and the modification of nanopores with methyl groups were discussed. It was found that the enantioselectivities increased with decreasing the nanopore sizes or increasing the linkage length in nanopore, and the Mn(salen) catalyst immobilized into nanopores generally gave higher ee values than those on the external surface. The heterogeneous Mn(salen) catalysts with modified nanopores gave a TOF of 14.8 h-1 and an ee value of 90.6% for the asymmetric epoxidation of 6-cyano-2,2-dimethylchromene, which were higher than the results (TOF 10.8 h-1, ee 80.1%) obtained for the homogeneous catalyst.
- Zhang, Huidong,Li, Can
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p. 6640 - 6649
(2007/10/03)
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