- Colloidal gold nanoparticles: An unexpected catalytic activity in aqueous phase with dioxygen
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Selective oxidations of alkenes were investigated using molecular oxygen in aqueous solution under mild conditions. Colloidal gold nanoparticles are particularly versatile catalysts for oxidation reaction with exceptionally high efficiency and significant selectivity. Gold nanorods (Au NRs) exhibited a slightly enhanced activity compare to gold nanospheres.
- Salari, Hadi,Robatjazi, Hossein,Hormozi-Nezhad, Mohammad Reza,Padervand, Mohsen,Gholami, Mohammad Reza
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- Alkoxysilylation of Ti-MWW lamellar precursors into interlayer pore-expanded titanosilicates
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Silylation of Ti-MWW lamellar precursor and subsequent calcination constructed an interlayer expanded structure, leading to novel titanosilicates with large pores. The silylating agents suitable for pore expansion were diethoxydimethylsilane, trimethylethoxysilane and triethoxymethylsilane containing methyl groups, which inhibited the intermolecular condensation of silanes effectively. In contrast to well-known 3D Ti-MWW with only medium pores of 10-membered rings, the silylation led to new crystalline structures with more open pores by ca. 2.5 A, as evidenced by the shift of layer-related diffractions to the lower-angle region in XRD patterns and the enlarged interlayer pores in HRTEM images. The interlayer expanded Ti-MWW was prepared readily from the corresponding hydrothermally synthesized precursors with a wide range of Ti contents (Si/Ti = 20-100). In addition, the pore expansion by silylation was realized under mild acid conditions with 0.1 M HNO3. The interlayer expanded Ti-MWW exhibited 3-7 times higher turnover number than 3D Ti-MWW in the oxidation of cyclohexene with H2O2. The Royal Society of Chemistry 2009.
- Wang, Lingling,Wang, Yong,Liu, Yueming,Wu, Haihong,Li, Xiaohong,He, Mingyuan,Wu, Peng
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- Catalytic olefin epoxidation over cobalt(ii)-containing mesoporous silica by molecular oxygen in dimethylformamide medium
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A cobalt(ii) Schiff base complex has been immobilized onto the surface of Si-MCM-41 to prepare a new catalyst. The amine group-containing organic moiety 3-aminopropyl-triethoxysilane had first been anchored on the surface of Si-MCM-41 via a silicon alkoxide route. Upon condensation with salicylaldehyde, the amine group affords a bidentate Schiff-base moiety in the mesoporous matrix, which is subsequently used for anchoring of cobalt(ii) centers. The prepared catalyst has been characterized by UV-vis, infrared (IR), EPR spectroscopic and small angle X-ray diffraction (XRD) analyses, and N2 sorption studies. The catalytic activity was tested in epoxidation reactions of olefinic compounds, including styrene and allyl alcohol, with molecular oxygen at atmospheric pressure in dimethylformamide medium in the absence of additional sacrificial reductant. The reactions seemed to proceed through a radical formation mechanism. The immobilized catalyst showed good activity and epoxide selectivity in the alkene epoxidation. Notably, the catalyst can be recovered and reused without any loss of activity. This journal is the Partner Organisations 2014.
- Bhunia, Susmita,Jana, Sreyashi,Saha, Debraj,Dutta, Buddhadeb,Koner, Subratanath
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- Fast catalytic epoxidation with H2O2 and [γ-SiW10O36(PhPO)2]4- in ionic liquids under microwave irradiation
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(Figure Presented) Olefin epoxidation by [γ-SiW10O 36(PhPO)2]4- and H2O2 occurs in hydrophobic ionic liquids (ILs), with yields and selectivity up to >99%. The catalytic IL phase is recyclable. Under MW irradiation the reaction occurs with up to 200 turnovers per minute. Simultaneous cooling is instrumental for quantitative H2O2 conversion.
- Berardi, Serena,Bonchio, Marcella,Carraro, Mauro,Conte, Valeria,Sartorel, Andrea,Scorrano, Gianfranco
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- Synthesis, spectroscopic characterization, thermal studies, catalytic epoxidation and biological activity of chromium and molybdenum hexacarbonyl bound to a novel N2O2 Schiff base
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Complexes of M(CO)6 (M = Cr and Mo) with novel Schiff base N,N′-bis(salicylidene)4,5-dichloro-1,2-phenylenediamine (H2L) were prepared in benzene in two different conditions: (i) under reduced pressure resulting the dicarbonyl precursors [Cr(CO)2(H2L)] and [Mo(CO)2(L)] and (ii) in air resulting the oxo complex [Cr(O)(L)] and the dioxo complex [Mo(O)2(L)]. The complexes were characterized by elemental analysis, IR, 1H NMR, mass spectrometry, and magnetic measurement. Thermal behaviors of the complexes were also studied by using thermogravimetric analysis (TGA). The catalytic activity of the novel complexes in the epoxidation of cyclooctene, cyclohexene, 1-octene and 1-hexene with tert-butyl-hydroperoxide (TBHP) in methylene chloride was investigated. The antimicrobial activities of the ligand and their complexes have been screened against various strains of bacteria and fungi and the results have been compared with some known antibiotics.
- Abdel Aziz, Ayman A.
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- Enhancement of alkene epoxidation activity of titanosilicates by gas-phase ammonia modification
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Novel ammonia-treated titanosilicates have been prepared by heating the samples of Ti-MWW, TS-1 and Ti-Beta under pure ammonia gas flow at 673 K for a period of time. The ammonia modification improved their catalytic performance in liquid-phase oxidations. Especially, the catalytic activities of ammonified Ti-MWW, N-Ti-MWW, were enhanced greatly in the epoxidation of 1-hexene with H2O2. The reason that the ammonia treatment played such an important role in post-modification of titanosilicate was investigated in details. In comparison to the parent Ti-MWW catalyst, N-Ti-MMW was more robust and produced less coke in oxidation reactions.
- Zhang, Liyan,Xu, Le,Sun, Jingjing,Jiang, Jingang,Liu, Yueming,Wu, Haihong,Wu, Peng
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- Nanoparticulate tungsten oxide for catalytic epoxidations
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A combination of spectroscopic and catalytic investigations led to the surprising conclusion that not isolated WVI species but WO 3 oxide is the most active and stable phase for olefin epoxidation with H2O2. Opt
- Hammond, Ceri,Straus, Julian,Righettoni, Marco,Pratsinis, Sotiris E.,Hermans, Ive
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- A recyclable hybrid manganese(III) porphyrin magnetic catalyst for selective olefin epoxidation using molecular oxygen
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The synthesis and characterization of a hybrid Mn(III)-porphyrin magnetic nanocomposite is described. Moreover, a sustainable methodology for epoxidation of olefins is reported, using O2 as a green oxidant and the magnetic nanoparticle as a rec
- Dias, Lucas D.,Carrilho, Rui M.B.,Henriques, César A.,Piccirillo, Giusi,Fernandes, Auguste,Rossi, Liane M.,Filipa Ribeiro,Calvete, Mário J.F.,Pereira, Mariette M.
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- Manganese(III) Tetraphenylporphyrin Encapsulated by Ion-Modified Hexagonal Mesoporous Silica With Unexpected Enhanced Epoxidation Selectivity
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Tetraphenylporphyrin manganese (III) chloride (Mn-TPP) was encapsulated into hexagonal mesoporous silica (HMS) modified by different Lewis acid ions Al, Ti, Zr, and W, which have been tested for selective oxidation of unsaturated olefins and more challeng
- Zhang, Weijie,Jiang, Pingping,Wang, Ying,Zhang, Jian,Zhang, Pingbo
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- Highly effective peroxidic epoxidation of olefins using hexathiocyanatorhenate(IV) as catalyst and bicarbonate as co-catalyst
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In the presence of bicarbonate as co-catalyst hexathiocyanatorhenate(IV) functions as an extremely effective catalyst in the epoxidation of olefins using aqueous hydrogen peroxide as the terminal oxidant.
- Dinda, Subhajit,Roy Chowdhury, Sujoy,Abdul Malik,Bhattacharyya, Ramgopal
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- Schiff base-functionalized boehmite nanoparticle-supported molybdenum and vanadium complexes: Efficient catalysts for the epoxidation of alkenes
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Boehmite nanoparticles were prepared using aluminium 2-butoxide. They were covalently functionalized with 3-(trimethoxysilyl)propylamine, after which all the terminal amine groups were changed to Schiff base by refluxing with salicylaldehyde in order to support vanadium oxosulfate and molybdenum hexacarbonyl complexes. These catalysts were applied in the epoxidation of olefins with tert-BuOOH in CCl4. The catalytic procedures for both catalysts were optimized for various parameters such as solvent, oxidant, temperature and time.
- Mirzaee, Mahdi,Bahramian, Bahram,Amoli, Adonis
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- Methyltrioxorhenium/pyrazole - A highly efficient catalyst for the epoxidation of olefins
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A biphasic system consisting of 35% H2O2 and methyltrioxorhenium(VII)/pyrazole in CH2Cl2 catalyzes the epoxidation of a wide range of olefins in excellent yields. Both the reactivity and selectivity of the new c
- Herrmann, Wolfgang A.,Kratzer, Roland M.,Ding, Hao,Thiel, Werner R.,Glas, Holger
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- A hexanuclear cobalt(II) cluster incorporated in a banana-shaped tungstovanadate: [(Co(OH2)Co2VW9O 34)2(VW6O26)]17-
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The hexanuclear cobalt-containing tungstovanadate complex, Na 17[(Co(OH2)Co2VW9O 34)2(VW6O26)]·31H 2O (1) has been synthesized through reaction of cobalt nitrate, sodium tungstate, and V2O5 in acetate buffer solution. The title compound has been characterized by X-ray crystallography, elemental analysis, FTIR, UV/Vis, and 51V NMR spectroscopy and by cyclic voltammetry. Complex 1 crystallizes in the monoclinic space group P2 1/c (a = 15.706(3) A, b = 21.973(5) A, c = 35.080(8) A, α = 90°, β = 97.420(3)°, γ = 90°; V = 12005(5) A3; Z = 4; based on 192337 independent reflections), which consists of two tri-CoII substituted B-α-[(Co(OH 2)Co2VW9O39)] Keggin units bridged by one unique [VW6O16] fragment leading to a banana-shaped structure with idealized C2ν symmetry. Stability studies show that polyoxoanion 1 ultimately transforms into the tetracobalt-containing sandwich-type polyoxoanion, 2, as confirmed by 51V NMR and X-ray crystallographic analyses. Polyoxoanion 1 shows catalytic activity for the H2O2-based epoxidation of 1-hexene and cyclohexene in 1,2-dichloroethane solvent. Copyright
- Lv, Hongjin,Song, Jie,Geletii, Yurii V.,Guo, Weiwei,Bacsa, John,Hill, Craig L.
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- Hydrogen peroxide activation by fluorophilic polyoxotungstates for fast and selective oxygen transfer catalysis
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Fluorophilic polyoxotungstates perform the selective epoxidations of internal and terminal double bonds by hydrogen peroxide (H2O2) activation in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), under mild temperature conditions. A hybrid synergy of supramolecular interactions, involving the inorganic cluster and the fluorinated solvent, is envisaged to boost H2O2 activation and the oxygen transfer mechanism. 1,2-Epoxides have been obtained with >99% selectivity and 98% yield at T = 40-70 °C.
- Carraro, Mauro,Gardan, Martino,Sartorel, Andrea,Maccato, Chiara,Bonchio, Marcella
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- Non-redox metal ions accelerated oxygen atom transfer by Mn-Me3tacn complex with H2O2 as oxygen resource
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This work demonstrates a novel strategy that the introduction of non-redox metal ions as Lewis acids to the classic dinuclear manganese complex [MnIV2(μ-O)3(Me3tacn)2](PF6)2 can greatly promote the alkene epoxidation efficiency under mild conditions with H2O2 as the solely terminal oxidant because of its economic and environmental advantages. When [MnIV2(μ-O)3(Me3tacn)2](PF6)2 was used as the catalyst in the absence of Lewis acids, only 16.4% conversion of cyclooctene with 6.2% yield of epoxide was obtained and the obvious decomposition of H2O2 was observed. However, the oxygen transfer efficiency of the catalyst was sharply improved with 100% conversion and 90.2% yield of epoxide under identical conditions when the non-redox metal ion, such as Sc3+, was introduced to the catalytic system. The novel strategy was successfully applied to the epoxidation reactions of different types of alkenes. Through UV–vis, FT-IR, EPR and CV characterizations, it was evidenced that the non-redox metal ions with high positive charge as Lewis acids could dissociate the sluggish dinuclear Mn-(μ-O)3-Mn core and the open-loop dinuclear manganese complex, HO-MnIII-(μ-O)-MnIV = O or O = MnIV-(μ-O)-MnIV = O, was proposed as the active species, which was capable of the alkene epoxidation process. This work illustrated an alternative protocol to manipulate the reactivity of those sluggish catalysts by the introduction of non-redox metal ions and provided clues to understand the role of non-redox metal ions in metalloenzymes and heterogeneous catalysts.
- Lv, Zhanao,Choe, Cholho,Wu, Yunfeng,Wang, Haibin,Chen, Zhuqi,Li, Guangxing,Yin, Guochuan
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- Scope and limitations of one-pot multistep reactions with heterogeneous catalysts: The case of alkene epoxidation coupled to epoxide ring-opening
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The combination of two reactions in one-pot multistep system requires the compatibility not only between the catalysts of both reactions, but also between all the reaction components and conditions. In the case of the coupling of alkene epoxidation and epoxide ring opening, it has been possible to synthesize cyanohydrin and azidohydrin derivatives through a simple process that involves a one-pot multistep process by using a mixture of two heterogeneous catalysts, a silica-grafted Ti catalyst and ytterbium chloride, whose efficiency depends on the reactivity of the starting alkene. In addition, in some cases the mixture of catalysts can be recovered and reused in several one-pot multistep cycles. However, this system is not possible with electron-deficient alkenes, as the basic catalyst required for epoxidation has shown to be incompatible with the ring-opening process.
- Fraile, José M.,García, Nuria,Herrerías, Clara I.,Mayoral, José A.
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- Synthesis and catalytic activity of Ti-ITQ-7: A new oxidation catalyst with a three-dimensional system of large pore channels
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Isomorphous substitution of Si by Ti in the framework of ITQ-7, the crystalline silica polymorph of lowest density, has been achieved by direct synthesis, affording its three dimensional system of large pore channels to be used in selective oxidation reactions.
- Diaz-Cabanas, Maria-Jose,Villaescusa, Luis A.,Camblor, Miguel A.
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- Oxidation of Olefins with Hydrogen Peroxide and tert-Butyl Hydroperoxide on Ti-Beta Catalyst
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The oxidation of a number of linear, branched, and cyclic olefins catalyzed by the large-pore Ti-Beta catalyst in the presence of H2O2 and TBHP as oxidants has been carried out under mild conditions.The influence of the olefin structure on its reactivity towards oxidation has been studied.Depending on the particular olefin structure, the reaction rate was seen to be mostly influenced by the intrinsic reactivity of the double bond, diffusional limitations, or steric factors.The latter were seen to be more pronounced in the oxidations with TBHP, owing to the bulkier Ti-OO-C(CH3)3 species which would be formed inside the zeolite pores.Oxidations with TBHP also proceeded at a lower rate than with H2O2.Close to 100percent selectivities to epoxides were found when TBHP was used as oxygen donor.In the case of H2O2 solvolysis of the oxirane ring in methanol solutions was the major secondary reaction observed.The rate of this reaction was seen to depend on the structure of the epoxide formed in the first step.In both cases, very little peroxide decomposition was observed under the reaction conditions used.
- Corma, A.,Esteve, P.,Martinez, A.,Valencia, S.
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- Molybdenum and Tungsten Carbonyl Complexes with N2 Schiff Base Donors: Syntheses, Spectral, Electrochemical, Thermal, Catalytic Epoxidation, and Biological Activity Studies
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Thermal reactions of Mo(CO)6 with the Schiff base 4-nitro-N-(pyridine-2-yl-methylene)aniline (NPMA) in THF in absence and presence of triphenyl phosphine (PPh3), pyridine (py) or thiourea (Tu) gave the four carbonyl complexes, [Mo(CO
- Mohamed, Rania G.,Elantabli, Fatma M.,Helal, Nadia H.,El-Medani, Samir M.
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- Selective oxidation of olefins with aqueous hydrogen peroxide over phosphomolybdic acid functionalized knitting aryl network polymer
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A phosphomolybdic acid (PMA)-based heterogeneous catalyst, denoted as PMA/KAP, was prepared by immobilizing PMA onto a knitting aryl network polymer (KAP) based on triphenylphosphine (PPh3). The catalytic property of PMA/KAP was investigated for the selective oxidation of olefins with aqueous hydrogen peroxide (H2O2) as oxidant. When using ethyl acetate (EAC) as reaction medium, PMA/KAP performs higher activity and selectivity to epoxide for a variety of olefins, and it can be reused for several times without obvious loss of activity. When the reaction was carried out in acetonitrile (AN) medium, deactivation of PMA/KAP catalyst can be observed immediately. A variety of characterization results suggest that the degradation of PMA unit to (PO4[MoO(O2)2]4)3- occurs easily when the PMA/KAP catalyst is operated in H2O2/AN system, while such degradation behavior could be significantly inhibited when the catalyst is used in the system of H2O2/EAC. We proposed that the neighbouring P-containing ligands dispersed in the framework of KAP can produce a steric pocket with low electron density, which can promote the formation of multi-weak coordination interaction between PMA unit and several P ligands. Such multi-weak interaction can inhibit the degradation of PMA to (PO4[MoO(O2)2]4)3-, thus avoiding the leaching of active species from the KAP support, and resulting in the formation of relatively stable heterogeneous PMA supported catalyst for olefin epoxidation with H2O2 in the media of EAC.
- Song, Xiaojing,Zhu, Wanchun,Yan, Yan,Gao, Hongcheng,Gao, Wenxiu,Zhang, Wenxiang,Jia, Mingjun
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- Synthesis of a silicalite-1-coated titanium silicalite-1 (TS-1) zeolite and its catalytic activity in liquid-phase oxidation
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Silicalite-1/titanium silicalite-1 (TS-1) composites were synthesized by growing silicalite-1 on the surface of TS-1. Oxidation of 1-hexene was studied using both the silicalite-1/TS-1 composite and uncoated TS-1. The silicalite-1/TS-1 composite showed a higher selectivity toward 1,2-epoxyhexane than uncoated TS-1 because sequential reactions on the external surface of TS-1 were inhibited. The catalytic activity of the silicalite-1/TS-1 composite was almost the same as that of TS-1, suggesting that the silicalite-1 layer is very thin and that the diffusion resistance is negligibly small.
- Sugiura, Yusuke,Hirota, Yuichiro,Uchida, Yoshiaki,Nishiyama, Norikazu
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- Synthesis, Crystal Structures, and Catalytic Properties of Dioxomolybdenum(VI) Complexes Derived from 4-Chloro-2-{[4-Diethylamino-2-Hydroxybenzylidene]amino}phenol
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Abstract: Two new dioxomolybdenum(VI) complexes, [MoO2L(EtOH)] (I) and [MoO2L(Sal)] (II), where L is the dianionic form of 4-chloro-2-{[4-(diethylamino)-2-hydroxybenzylidene]amino}phenol (H2L), Sal is 4-diethylaminosalicyl
- Zhu
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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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- Catalytic performance of [Ti,Al]-beta in the alkene epoxidation controlled by the postsynthetic ion exchange
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The catalytic performance of [Ti,Al]-Beta in the alkene epoxidation controlled by the postsynthetic ion exchange was studied. When as-synthesized [Ti,Al]-Beta was treated with aqueous ammonium nitrate solution and successively calcined at low temperature, a dramatic enhancement of epoxide selectivity was attained in the liquid-phase epoxidation of cyclohexene using H2O2 as an oxidant in protic solvent methanol. Addition of H2O2 to the system of three non-titanosilicates (H-ZSM-5, silicalite-1, and deboronated B-Beta) produced no enhancement effect in the solvolysis of cyclohexene oxide. The optimum thermal treatment temperature to achieve the maximum epoxide yield was 473 K, where the postsynthetic [Ti,Al]-Beta exhibited a catalytic activity comparable to the sample directly calcined at 793 K; nevertheless, the epoxide selectivity was ≤ 63% for the former in contrast to 0% for the latter. [Ti,Al]-Beta ion-exchanged with quaternary ammonium acetate followed by mild calcination showed similarly high epoxide selectivity. Tetramethylammonium acetate was the best modifier, resulting in almost no loss of epoxidation activity. Regeneration of the ion-exchange treatments catalysts was achieved by the repeated calcination and ion-exchange treatments, making the catalyst reusable. The pH in the ion-exchange treatment strongly influenced the catalytic performance. The optimal pH of the treatments was ~ 10. High pH treatments caused the partial dissolution of [Ti,Al]-Beta frameworks to increase the activity but decreased the epoxide selectivity.
- Goa, Yasuhide,Wu, Peng,Tatsumi, Takashi
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- Synthesis of an Ultralarge Pore Titanium Silicate Isomorphous to MCM-41 and its Application as a Catalyst for Selective Oxidation of Hydrocarbons
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An ultralarge pore titanium silicate with MCM-41 structure has been prepared by direct hydrothermal synthesis; this material gives rise to useful catalysts for the selective oxidation of small and large organic compounds.
- Corma, A.,Navarro, M. T.,Pariente, J. Perez
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- Alkylaminophosphazenes as Efficient and Tuneable Phase-Transfer Agents for Polyoxometalate-Catalysed Biphasic Oxidation with Hydrogen Peroxide
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Alkylaminophosphazenes (RPN) are efficient and tuneable phase-transfer agents for environmentally benign biphasic oxidation with hydrogen peroxide catalysed by polyoxometalates (POMs). Substituent groups on the phosphazene ring can be varied to modify the
- Craven, Michael,Yahya, Rana,Kozhevnikova, Elena F.,Robertson, Craig M.,Steiner, Alexander,Kozhevnikov, Ivan V.
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- Hydrophobicity enhancement of Ti-MWW catalyst and its improvement in oxidation activity
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The effect of the preparation conditions of the Ti-MWW catalyst on the hydrophobicity of the catalyst and its catalytic activity was investigated. Our findings demonstrated that the condensation of interlayer hydroxyl groups was greatly affected by the preparation conditions, in particular washing conditions of the as-synthesized lamellar precursor of Ti-MWW, then further controlling the final hydrophobicity and oxidation properties. Using organic solvents, especially EAOH, instead of water to wash the wet lamellar precursor would synchronize the interlayer hydroxyl condensation with the decrease of interlayer distance mainly caused by the leaching of piperidine, which was used as structure-directing agent (SDA). After acid-treatment, less SDA was kept in the EAOH washed sample and 3D-MWW with less defects was formed by calcination. Both drying temperature and acid-treatment would also affect the amount of SDA occluded in the interlayer void space of the acid-treated samples and then further affect the final interlayer hydroxyl condensation upon the following calcination. The lower both drying temperature and acid-treatment temperature were favorite to unequal interlayer dehydroxylation to form MCM-56, while higher drying temperature such as 150 C not only caused the anatase phase in the calcined samples but also occluded more SDA molecules in the acid-treated samples which greatly affect the further interlayer hydroxyl condensation upon the calcination. Ti-MWW-OH-100 containing smallest amount of silanols and less defect sites showed the best hydrophobicity and the highest catalytic activity in 1-hexene oxidation.
- Zhao, Hong,Yokoi, Toshiyuki,Kondo, Junko N.,Tatsumi, Takashi
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- Anchoring of copper(II) complexes onto the organically modified MCM-41: Preparation, characterization and catalytic epoxidation
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[Cu(diamine)(NO3)2] complexes have been anchored by substituting easily replaceable nitrate ligand with the amine groups of the organic-modified MCM-41. The amine group containing organic moiety (3-aminopropyl)triethoxysilane has been first anchored on the surface of MCM-41 via silicon alkoxide route. Then the [Cu(diamine)(NO3)2] [where diamine = N,N′-dimethyl-1,2-ethanediamine (NN′dmen) N,N-dimethyl-1,2-ethanediamine (NNdmen), and N,N-diethyl-1,2-ethanediamine (NNdeten)] complex was allowed to react with the modified MCM-41 for tethering the complexes onto mesoporous silica matrix. Copper complexes containing different substituted diamine ligands viz. N,N′-dimethyl-1,2- ethanediamine, N,N-dimethyl-1,2-ethanediamine, and N,N-diethyl-1,2-ethanediamine have also been prepared to compare the catalytic efficiency. The prepared catalysts have been characterized by infrared (FT-IR) and UV-vis spectroscopic, electron paramagnetic resonance (EPR), small-angle X-ray diffraction and N 2 sorption study. The catalytic efficacy in the epoxidation reaction depends on the bulkiness of the substituted group in diamine. Notably, styrene shows an impressive conversion (94%) with tert-butylhydroperoxide (tert-BuOOH) over the Cu(NNdmen)-MCM-41 catalyst. Whereas, conversion in styrene to styrene-oxide reaction were only 78% and 48% with Cu(NNdeten)-MCM-41 and Cu(NN′dmen)-MCM-41 catalysts, respectively.
- Jana, Sreyashi,Bhunia, Susmita,Dutta, Buddhadeb,Koner, Subratanath
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- Olefin epoxidation with hydrogen peroxide using octamolybdate-based self-separating catalysts
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Mo8O264- based organic polyoxomolybdate salts of general formula [Hmim]4Mo8O26 (Hmim = 1-hexyl-3-methylimidazolium), [Dhmim]4Mo8O26 (Dhmim = 1,2-dimethyl-3-hexylimidazolium) and [Hpy]4Mo8O26·H2O (Hpy = 1-hexylpyridinium) have been prepared and characterized. These compounds were applied as catalysts for olefin epoxidation using hydrogen peroxide (H2O2) as oxidant in CH3CN. The polyoxomolybdate salts exhibit excellent catalytic performance and are also self-separating, a great advantage for catalyst recycling. The catalysts can be reused for at least 10 runs without significant loss of activity. This journal is
- Zhou, Ming-Dong,Liu, Mei-Ju,Huang, Liang-Liang,Zhang, Jian,Wang, Jing-Yun,Li, Xue-Bing,Kühn, Fritz E.,Zang, Shu-Liang
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- Catalysis of the epoxidation of olefins
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By analogy between the oxo forms of vanadium (V) and iron (IV), the latter being the active species in oxidations by cytochrome P-450, the system constituted by vanadium oxide (catalyst) and 6-butylhydroperoxide (oxidant) gives good results in the conversion of olefins to the corresponding epoxides.
- Laszlo,Levart,Singh
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- Stereochemistry of the biotransformation of 1-hexene and 2-methyl-1- hexene with rat liver microsomes and purified p450s of rats and humans
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The epoxidation of 1-hexene (1a) and 2-methyl-1-hexene (1b), two hydrocarbons present in the ambient air as pollutants, is catalyzed by some human and rat P450 enzymes. The enantioselectivities of these processes, when the reactions were carried out using rat and human liver microsomal preparations, were modest and dependent on both P450 composition and substrate concentrations. Various P450 isoforms (rat P450 2B1 and human P450 2C10 and 2A6) catalyzed the double bond oxidation of 1a and 1b with different product enantioselectivities. In the case of 1a, a moderately enantioselective hydroxylation at the allylic C(3) with the formation of 1- hexen-3-ol (4a) by microsomes from control or preinduced rats was also observed. The oxidation of this metabolite was, in turn, catalyzed by rat liver microsomes and mainly by rat P450 2C11, leading exclusively to the formation of 1-hexen-3-one, with no double bond epoxidation being observed. The stereochemical course of the microsomal epoxide hydrolase-catalyzed hydrolysis of the epoxy alcohols, threo-(±)- and erythro-(±)-1,2- epoxyhexan-3-ol, theoretically expected to be formed from 4a, has been investigated.
- Chiappe, Cinzia,De Rubertis, Antonietta,Amato, Giada,Gervasi, Pier Giovanni
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- In situ fabricated MOF-cellulose composite as an advanced ROS deactivator-convertor: Fluoroswitchable bi-phasic tweezers for free chlorine detoxification and size-exclusive catalytic insertion of aqueous H2O2
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Combining the merits of structural diversity, and purposeful implantation of task-specific functionalities, metal-organic frameworks (MOFs) instigate targeted reactive oxygen species (ROS) scavenging and concurrent detoxification via self-calibrated emission modulation. Then again, grafting of catalytically active sites in MOFs can benefit developing a greener protocol to convert ROS generators to technologically important building blocks, wherein tailorable MOF-composite fabrication is highly sought for practical applications, yet unexplored. The chemo-robust and hydrogen-bonded framework encompassing free -NH2 moiety affixed pores serves as an ultra-fast and highly regenerable fluoro-probe for selective detection of toxic ROS producers hypochlorite ion (ClO-) and H2O2 with record-level nanomolar sensitivity. While the bio-relevant antioxidant l-ascorbic acid (AA) imparts notable quenching to the MOF, a significant 3.5 fold emission enhancement with bi-phasic colorimetric variation ensues when it selectively scavenges ClO- from uni-directional porous channels through an unprecedented molecular tweezer approach. Apart from a battery of experimental evidence, density functional theory (DFT) results validate "on-off-on"fluoroswitching from redistribution of MOF orbital energy levels, and show guest-mediated exclusive transition from "Tight state"to "Loose state". The coordination frustrated metal site engineered pore-wall benefits the dual-functionalized MOF in converting the potential ROS generator H2O2via selective alkene epoxidation under mild-conditions. Importantly, sterically encumbered substrates exhibit poor conversion and demonstrate first-ever pore-fitting-induced size selectivity for this benign oxidation. Judiciously planned control experiments in combination with DFT-optimized intermediates provide proof-of-concept to the ionic route of ROS conversion. Considering an effective way to broaden the advanced applications of this crystalline material, reconfigurable MOF@cotton fiber (CF) is fabricated via in situ growth, which scavenges free chlorine and concomitantly squeezes it upon exposure to AA with obvious colorimetric changes over multiple real-life platforms. Furthermore, multi-cyclic alkene epoxidation by MOF@CF paves the way to futuristic continuous flow reactors that truly serves this smart composite as a bimodal ROS deactivator-convertor and explicitly denotes it as an advanced promising analogue from contemporary state-of-the-art materials.
- Bankar, Balasaheb D.,Biradar, Ankush V.,Goswami, Ranadip,Neogi, Subhadip,Pillai, Renjith S.,Rajput, Sonal,Seal, Nilanjan
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p. 4316 - 4332
(2022/03/07)
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- MCM-41 supported heterogeneous catalyst for the conversion of alkene to epoxide: Synthesis, characterization and catalytic studies
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A new hybrid catalyst has been prepared by the immobilization of copper(II) α-diimine complex on the surface of mesoporous silica, MCM-41. The symmetrical α-diimine ligand has been prepared from dimethyl glyoxal and p-amino benzoic acid (PABA). The catalyst has been characterized by different analytical techniques such as elemental analysis, FT-IR, N2 sorption, small angle X-ray diffraction, thermogravimetric analysis (TGA), SEM and TEM. The PXRD and TEM measurements showed that the heterogeneous catalyst has mesoporosity. The catalyst has been tested in the conversion of alkene into epoxide using tert-butyl-hydroperoxide (tert-BuOOH) as oxidant in acetonitrile medium. The maximum yield (100%) was obtained with trans stilbene. The compared catalytic studies demonstrated that this catalyst is more effective in terms of reactivity and stability than its counter parts. This can be recycled and reused several times without significant loss of activity.
- Sharma, Saurabh,Singh, Udai P.
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- Synthesis, characterization and catalytic activities of nonheme manganese(III) complexes: Preferential formation of cis olefin oxide owing to steric hindrance
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Three mononuclear nonheme MnIII(salophen) complexes, 1a-1c, with tetradentate ligands containing two deprotonated phenolates ([(X2-tert-butyl-salophen)Mn(OAc)(H2O)] (tert-butyl-salophen = N,N′-bis(6-di-tert-butylsalicylidene)-1,2-phenylenediaminato, 1a for X = Cl, 1b for X = H, and 1c for X = CH3)) were synthesized and characterized using 1H NMR, 13C NMR, elemental analysis and ESI-Mass spectrometry. These Mn(III) complexes were used to efficiently catalyze the epoxidation reactions of diverse aliphatic, aromatic and terminal alkenes to form the corresponding epoxides with MCPBA (m-chloroperoxybenzoic acid) as an oxidant under mild conditions. Notably, catalysts 1a-1c preferably react with the cis-alkene because of the steric hindrance between the reactive intermediate MnIII-OOC(O)R and the trans-type substrate. A Hammett study and product analysis using PPAA (peroxyphenylacetic acid) as a mechanistic indicator suggested that the peracid reacted with the Mn(III) complex to generate the MnIII-OOC(O)R intermediate, which underwent both homolysis and heterolysis to form MnIV=O or MnV=O. The reactive MnV=O might participate in the alkene epoxidation with good stereospecificity, whereas the MnIV=O species might trigger radical-type oxidation to produce non-stereospecific by-products, such as ketones and aldehyde. On the other hand, MnIII-OOC(O)R (2) could oxidize the reactive cyclohexene to the epoxide, whereas it was unable to epoxidize the poorly reactive 1-octene.
- Kim, Cheal,Lee, Jiyoung,Moon, Sungjin,Park, Soyoung
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- Rhenium-containing compound(PyHReO4): synthesis, characterization and catalytic application in olefin epoxidation and baeyer-villiger oxidation
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A novel compound based on catalytic functional metal rhenium, pyridinium perrhenate(PyHReO4) was synthesized and characterized. The pyridinium perrhenate was used as catalyst in two types of reactions. One is the epoxidation of cyclooctene, the other is the Baeyer-Villiger oxidation of cyclic ketones to lactones. The effects of catalyst, oxidant, solvent, reaction time and temperature were investigated, which confirmed the optimum reaction conditions of the catalyst system. Both types of catalytic reactions exhibit high yields and high selectivity. Graphical abstract: The synthesized novel compound based on catalytic functional metal rhenium, pyridinium perrhenate(PyHReO4) exhibit excellent catalytic activity. The system with PyHReO4 as a catalyst provided an effective, easy separation, mild and convenient method in two different types of reactions(One is the epoxidation of cyclooctene, the other is the Baeyer-Villiger oxidation of 2-adamantanone). [Figure not available: see fulltext.]
- Dong, Yingnan,Li, Yucai,Song, Shiwei,Wang, Gang,Wang, Han,Wang, Jian,Wang, Shuaijie,Zhang, Dong,Zhao, Yan
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- Proton Switch in the Secondary Coordination Sphere to Control Catalytic Events at the Metal Center: Biomimetic Oxo Transfer Chemistry of Nickel Amidate Complex
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High-valent metal-oxo species are key intermediates for the oxygen atom transfer step in the catalytic cycles of many metalloenzymes. While the redox-active metal centers of such enzymes are typically supported by anionic amino acid side chains or porphyrin rings, peptide backbones might function as strong electron-donating ligands to stabilize high oxidation states. To test the feasibility of this idea in synthetic settings, we have prepared a nickel(II) complex of new amido multidentate ligand. The mononuclear nickel complex of this N5 ligand catalyzes epoxidation reactions of a wide range of olefins by using mCPBA as a terminal oxidant. Notably, a remarkably high catalytic efficiency and selectivity were observed for terminal olefin substrates. We found that protonation of the secondary coordination sphere serves as the entry point to the catalytic cycle, in which high-valent nickel species is subsequently formed to carry out oxo-transfer reactions. A conceptually parallel process might allow metalloenzymes to control the catalytic cycle in the primary coordination sphere by using proton switch in the secondary coordination sphere.
- Kim, Soohyung,Jeong, Ha Young,Kim, Seonghan,Kim, Hongsik,Lee, Sojeong,Cho, Jaeheung,Kim, Cheal,Lee, Dongwhan
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supporting information
p. 4700 - 4708
(2021/02/12)
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- Nonheme manganese(III) complexes for various olefin epoxidation: Synthesis, characterization and catalytic activity
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Three mononuclear imine-based non-heme manganese(III) complexes with tetradentate ligands which have two deprotonated phenolate moieties, ([(X2saloph)Mn(OAc)(H2O)], 1a for X = Cl, 1b for X = H, and 1c for X = CH3, saloph = N,N-o-phenylenebis(salicylidenaminato)), were synthesized and characterized by 1H NMR, 13C NMR, ESI-Mass and elemental analysis. MnIII complexes catalysed efficiently various olefin epoxidation reactions with meta-chloroperbenzoic acid (MCPBA) under the mild condition. MnIII complexes 1a and 1c with the electron-withdrawing group -Cl and electron-donating group –CH3 showed little substituent effect on the epoxidation reactions. Product analysis, Hammett study and competition experiments with cis- and trans-2-octene suggested that MnIV = O, MnV = O, and MnIII-OOC(O)R species might be key oxidants in the epoxidation reaction under this catalytic system. In addition, the use of PPAA as a mechanistic probe demonstrated that Mn-acylperoxo intermediate (MnIII-OOC(O)R) 2 generated from the reaction of peracid with manganese complexes underwent both the heterolysis and the homolysis to produce MnV = O (3) or MnIV = O species (4). Moreover, the MnIII-OOC(O)R 2 species could react directly with the easy-to-oxidize substrate to give epoxide, whereas the species 2 might not be competent to the difficult-to-oxidize substrate for the epoxidation reaction.
- Lee, Sojeong,Park, Soyoung,Lee, Myoung Mi,Lee, Jiyoung,Kim, Cheal
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- An Amphiphilic (salen)Co Complex – Utilizing Hydrophobic Interactions to Enhance the Efficiency of a Cooperative Catalyst
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An amphiphilic (salen)Co(III) complex is presented that accelerates the hydrolytic kinetic resolution (HKR) of epoxides almost 10 times faster than catalysts from commercially available sources. This was achieved by introducing hydrophobic chains that increase the rate of reaction in one of two ways – by enhancing cooperativity under homogeneous conditions, and increasing the interfacial area under biphasic reaction conditions. While numerous strategies have been employed to increase the efficiency of cooperative catalysts, the utilization of hydrophobic interactions is scarce. With the recent upsurge in green chemistry methods that conduct reactions ‘on water’ and at the oil-water interface, the introduction of hydrophobic interactions has potential to become a general strategy for enhancing the catalytic efficiency of cooperative catalytic systems. (Figure presented.).
- Solís-Mu?ana, Pablo,Salam, Joanne,Ren, Chloe Z.-J.,Carr, Bronte,Whitten, Andrew E.,Warr, Gregory G.,Chen, Jack L.-Y.
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supporting information
p. 3207 - 3213
(2021/06/01)
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- Tris-imidazolinium-based porous poly(ionic liquid)s as an efficient catalyst for decarboxylation of cyclic carbonate to epoxide
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A series of imidazolinium-based porous poly(ionic liquid)s (PILs) with different anions prepared by free-radical copolymerization of an arene-bridged tris-vinylimidazolium salt and divinylbenzene (DVB) were constructed. The as-prepared PILs were characterized by BET, SEM, TEM, TGA and Elemental Analysis (EA), and the results showed that they had plentiful ionic sites, and abundant and stable mesopores. In particular, the density of ionic sites and pore structure of PILs could be controlled by adjusting the content of DVB. Moreover, the PILs were used as efficient heterogeneous catalysts for the decarboxylation of cyclic carbonates to epoxides for the first time. Results showed that the catalytic activity of PILs was positively correlated with the nucleophilicity of the anions in PILs, and PDVB-[PhTVIM]Cl-1 with a chloride anion-enriched skeleton displayed the best catalytic performance. Without any solvent or cocatalyst, PDVB-[PhTVIM]Cl-1 achieved a TOF value of 108.1 h-1and the yield of butylene oxide of 89.6%, which was even better than the homogeneous IL-based catalysts (TOF value: 8.7 h-1) that had been previously reported. Meanwhile, PDVB-[PhTVIM]Cl-1 also exhibited excellent recyclability and substrate compatibility.
- Li, Yang,Wang, Liguo,Cao, Yan,Xu, Shuang,He, Peng,Li, Huiquan,Liu, Hui
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p. 14193 - 14202
(2021/04/22)
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- Cu(ii)Cl2containing bispyridine-based porous organic polymer support preparedviaalkyne-azide cycloaddition as a heterogeneous catalyst for oxidation of various olefins
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A new type of porous organic polymer (POP) based heterogeneous catalystCu-POPwas prepared by immobilizing Cu(ii)Cl2into bpy containing POP preparedviaalkyne-azide cycloaddition. This new catalyst showed efficient catalytic activities and outstanding reusability. Remarkably, one batch ofCu-POPwas continuously used for all olefins without losing its activity by simply washing.
- Choi, Hye Min,Lee, Suk Joong,Yoon, Jongho
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supporting information
p. 9149 - 9152
(2020/06/17)
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- Mixed tetradentate NHC/1,2,3-triazole iron complexes bearing cis labile coordination sites as highly active catalysts in Lewis and Br?nsted acid mediated olefin epoxidation
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Two bio-inspired non-heme iron complexes bearing mixed tetradentate N-heterocyclic carbene/1,2,3-triazole ligands with cis labile coordination sites are reported. The compounds are studied in olefin epoxidation catalysis using H2O2 as oxidant. Sc(OTf)3, HClO4 and HOAc are applied as additives resulting in significant improvement of catalytic performance. Under optimized conditions the most active catalyst exhibits activities of 76,000 turnovers per hour, which is the highest reported value for an iron(II) catalyst. The complexes reveal comparably high stability and enable the challenging epoxidation of functionalized olefins. These results prove 1,2,3-triazoles to be promising and tunable ligands for iron catalyzed oxidation reactions.
- Dyckhoff, Florian,Jakob, Christian H. G.,Kühn, Fritz E.,Nguyen, Linda,Reich, Robert M.,Schlagintweit, Jonas F.
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p. 144 - 152
(2020/02/04)
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- Stereospecific Epitaxial Growth of Bilayered Porous Molecular Networks
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Stereocontrolled multilayer growth of supramolecular porous networks at the interface between graphite and a solution was investigated. For this study, we designed a chiral dehydrobenzo[12]annulene (DBA) building block bearing alkoxy chains substituted at the 2 position with hydroxy groups, which enable van der Waals stabilization in a layer and potential hydrogen-bonding interactions between the layers. Bias voltage-dependent scanning tunneling microscopy (STM) experiments revealed the diastereospecificity of the bilayer with respect to both the intrinsic chirality of the building blocks and the supramolecular chirality of the self-assembled networks. Top and bottom layers within the same crystalline domain were composed of the same enantiomers but displayed opposite supramolecular chiralities.
- Fang, Yuan,Lindner, Benjamin D.,Destoop, Iris,Tsuji, Takashi,Zhang, Zhenzhe,Khaliullin, Rustam Z.,Perepichka, Dmitrii F.,Tahara, Kazukuni,Feyter, Steven De,Tobe, Yoshito
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supporting information
p. 8662 - 8671
(2020/12/23)
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- Conglomerated system of Ag nanoparticles decorated Al2O3 supported cobalt and copper complexes with enhanced catalytic activity for oxidation reactions
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In this study, our aim is to increase the effectiveness of heterogeneous catalysts by reducing its drawback. For this purpose we have developed a new method to synthesize heterogeneous catalyst by dispersion of Silver nanoparticles onto Alumina supported cobalt and copper Schiff base complexes (AgNPs-Al2O3@ML).Initially Schiff base and its corresponding Co (III) complex, (CoL) and Cu (II) complex, (CuL)(L = Schiff base) were synthesized. Both the complexes were immobilized on Al2O3 to generate Al2O3@CoL (HT1) and Al2O3@CuL (HT2). Finally, Silver was dispersed onto both the heterogeneous complexes to generate our desired heterogeneous catalyst Ag NPs-Al2O3@CoL (AgHT1) and Ag NPs-Al2O3@CuL (AgHT2).A hike in BET surface area from HT1 to AgHT1 highlighted the fruitfulness of decoration of Ag NPs onto HT1. FESEM studies of AgHT1 and AgHT2 reveal the formation of pyramidal type silver nanoparticle onto HT1 and HT2. The catalytic ability of CoL, CuL (homogeneous catalyst), HT1, HT2 and AgHT1, AgHT2 (heterogeneous catalyst) were investigated by enrolling it on oxidation of alcohols, alkanes and epoxidation of alkenes using H2O2 as oxidant. Among the four heterogeneous catalysts AgHT1 showed highest activity. Finally a plausible mechanism has been put forward to elucidate the role of each substituent of the catalytic system. The heterogeneous catalysts HT1, HT2, AgHT1 and AgHT2 can be reused up to six times without any significant loss in its catalytic activity.
- Chakraborty, Tonmoy,Chakraborty, Aratrika,Maity, Suvendu,Das, Debasis,Chattopadhyay, Tanmay
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p. 104 - 113
(2018/11/21)
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- Aromatic Donor-Acceptor Interaction-Based Co(III)-salen Self-Assemblies and Their Applications in Asymmetric Ring Opening of Epoxides
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Aromatic donor-acceptor interaction as the driving force to assemble cooperative catalysts is described. Pyrene/naphthalenediimide functionalized Co(III)-salen complexes self-assembled into bimetallic catalysts through aromatic donor-acceptor interactions and showed high catalytic activity and selectivity in the asymmetric ring opening of various epoxides. Control experiments, nuclear magnetic resonance (NMR) spectroscopy titrations, mass spectrometry measurement, and X-ray crystal structure analysis confirmed that the catalysts assembled based on the aromatic donor-acceptor interaction, which can be a valuable noncovalent interaction in supramolecular catalyst development.
- Liang, Jian,Soucie, Luke N.,Blechschmidt, Daniel R.,Yoder, Aaron,Gustafson, Addie,Liu, Yu
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supporting information
p. 513 - 518
(2019/01/14)
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- Polymer-anchored mononuclear and binuclear CuII Schiff-base complexes: Impact of heterogenization on liquid phase catalytic oxidation of a series of alkenes
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Liquid phase catalytic oxidation of a number of alkenes, for example, cyclohexene, cis-cyclooctene, styrene, 1-methyl cyclohexene and 1-hexene, was performed using polymer-anchored copper (II) complexes PS-[Cu (sal-sch)Cl] (5), PS-[Cu (sal-tch)Cl] (6), PS-[CH2{Cu (sal-sch)Cl}2] (7) and PS-[CH2{Cu (sal-tch)Cl}2] (8). Neat complexes [Cu (sal-sch)Cl] (1), [Cu (sal-tch)Cl] (2), [CH2{Cu (sal-sch)Cl}2] (3) and [CH2{Cu (sal-tch)Cl}2] (4) were isolated by reacting CuCl2·2H2O with [Hsal-sch] (I), [Hsal-tch] (II), [H2bissal-sch] (III) and [H2bissal-tch] (IV), respectively, in refluxing methanol. Complexes 1–4 have been covalently anchored in Merrifield resin through the amine nitrogen of the semicarbazide or thiosemicarbazide moiety. A number of analytical, spectroscopic and thermal techniques, such as CHNS analysis, Fourier transform-infrared, UV–Vis, PMR, 13C-NMR, electron paramagnetic resonance, scanning electron microscopy, energy-dispersive X-ray analysis, thermogravimetric analysis, atomic force microscopy, atomic absorption spectroscopy, and electrospray ionization-mass spectrometry, were used to analyze and establish the molecular structure of the ligands (I)–(IV) and complexes (1)–(8) in solid state as well as in solution state. Grafted complexes 5–8 were employed as active catalysts for the oxidation of a series of alkenes in the presence of hydrogen peroxide. Copper hydroperoxo species ([CuIII (sal-sch)-O-O-H]), which is believed to be the active intermediate, generated during the catalytic oxidation of alkenes, are identified. It was found that supported catalysts are very economical, green and efficient in contrast to their neat complexes as well as most of the recently reported heterogeneous catalysts.
- Maurya, Abhishek,Kesharwani, Neha,Kachhap, Payal,Mishra, Vivek Kumar,Chaudhary, Nikita,Haldar, Chanchal
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- Room Temperature Iron-Catalyzed Transfer Hydrogenation and Regioselective Deuteration of Carbon-Carbon Double Bonds
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An iron catalyst has been developed for the transfer hydrogenation of carbon-carbon multiple bonds. Using a well-defined β-diketiminate iron(II) precatalyst, a sacrificial amine and a borane, even simple, unactivated alkenes such as 1-hexene undergo hydrogenation within 1 h at room temperature. Tuning the reagent stoichiometry allows for semi- and complete hydrogenation of terminal alkynes. It is also possible to hydrogenate aminoalkenes and aminoalkynes without poisoning the catalyst through competitive amine ligation. Furthermore, by exploiting the separate protic and hydridic nature of the reagents, it is possible to regioselectively prepare monoisotopically labeled products. DFT calculations define a mechanism for the transfer hydrogenation of propene with nBuNH2 and HBpin that involves the initial formation of an iron(II)-hydride active species, 1,2-insertion of propene, and rate-limiting protonolysis of the resultant alkyl by the amine N-H bond. This mechanism is fully consistent with the selective deuteration studies, although the calculations also highlight alkene hydroboration and amine-borane dehydrocoupling as competitive processes. This was resolved by reassessing the nature of the active transfer hydrogenation agent: experimentally, a gel is observed in catalysis, and calculations suggest this can be formulated as an oligomeric species comprising H-bonded amine-borane adducts. Gel formation serves to reduce the effective concentrations of free HBpin and nBuNH2 and so disfavors both hydroboration and dehydrocoupling while allowing alkene migratory insertion (and hence transfer hydrogenation) to dominate.
- Espinal-Viguri, Maialen,Neale, Samuel E.,Coles, Nathan T.,MacGregor, Stuart A.,Webster, Ruth L.
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supporting information
p. 572 - 582
(2019/01/08)
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- Epoxidation of Cyclooctene Using Water as the Oxygen Atom Source at Manganese Oxide Electrocatalysts
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Epoxides are useful intermediates for the manufacture of a diverse set of chemical products. Current routes of olefin epoxidation either involve hazardous reagents or generate stoichiometric side products, leading to challenges in separation and significant waste streams. Here, we demonstrate a sustainable and safe route to epoxidize olefin substrates using water as the oxygen atom source at room temperature and ambient pressure. Manganese oxide nanoparticles (NPs) are shown to catalyze cyclooctene epoxidation with Faradaic efficiencies above 30%. Isotopic studies and detailed product analysis reveal an overall reaction in which water and cyclooctene are converted to cyclooctene oxide and hydrogen. Electrokinetic studies provide insights into the mechanism of olefin epoxidation, including an approximate first-order dependence on the substrate and water and a rate-determining step which involves the first electron transfer. We demonstrate that this new route can also achieve a cyclooctene conversion of ~50% over 4 h.
- Jin, Kyoungsuk,Maalouf, Joseph H.,Lazouski, Nikifar,Corbin, Nathan,Yang, Dengtao,Manthiram, Karthish
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supporting information
p. 6413 - 6418
(2019/05/02)
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- Enantioselective Resolution Copolymerization of Racemic Epoxides and Anhydrides: Efficient Approach for Stereoregular Polyesters and Chiral Epoxides
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Herein we report an efficient strategy for preparing isotactic polyesters and chiral epoxides via enantioselective resolution copolymerization of racemic terminal epoxides with anhydrides, mediated by enantiopure bimetallic complexes in conjunction with a nucleophilic cocatalyst. The chirality of both the axial linker and the diamine backbones of the ligand are responsible for the chiral induction of this kinetic resolution copolymerization process. The catalyst systems exhibit exceptional levels of enantioselectivity with a kinetic resolution coefficient exceeding 300 for various racemic epoxides, affording highly isotactic copolymers (selectivity factors of more than 300) with a completely alternating structure and low polydispersity index. Most of the produced isotactic polyesters are typical semicrystalline materials with melting temperatures in the range from 77 to 160 °C.
- Li, Jie,Ren, Bai-Hao,Wan, Zhao-Qian,Chen, Shi-Yu,Liu, Ye,Ren, Wei-Min,Lu, Xiao-Bing
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supporting information
p. 8937 - 8942
(2019/06/11)
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- Synthesis, Crystal Structure, and Catalytic Property of a Dioxomolybdenum(VI) Complex Derived from N'-(3-Bromo-5-Chloro-2-Hydroxybenzylidene)-4-Nitrobenzohydrazide
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New dioxomolybdenum(VI) complex [MoO2(L)(CH3OH)], where L is the dianionic form of N'- (3-bromo-5-chloro-2-hydroxybenzylidene)-4-nitrobenzohydrazide (H2L), was prepared and characterized by IR and UV-Vis spectra, as well as single crystal X-ray diffraction (CIF file ССDС no. 1567063). The complex crystallizes as the monoclinic space group P21/c with unit cell dimensions a = 13.8471(10), b = 7.5618(6), c = 17.9445(12) ?, β = 90.107(2)°, V = 1878.9(2) ?3, Z = 4, R1 = 0.0821, wR2 = 0.0907, GOOF = 1.024. X-ray analysis indicates that the complex is a dioxomolybdenum(VI) species with the Mo atom in octahedral coordination. The catalytic oxidation property of the complex with tert-butylhydroperoxide in CH2Cl2 was studied.
- Zhu
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p. 421 - 424
(2018/07/06)
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- Synthesis, crystal structures and catalytic property of dioxomolybdenum(VI) complexes derived from tridentate Schiff bases
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A pair of structurally similar new dioxomolybdenum(VI) complexes, [MoO2L1(EtOH)] · EtOH (1) and [MoO2L2(MeOH)] (2), where L1 and L2 are the dianionic form of 2-[(2-hydroxyphenylimino)methyl
- Zhu, Xue-Wen
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p. 939 - 945
(2019/02/15)
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- Mn(III)-Porphyrin Containing Heterogeneous Catalyst based on Microporous Polymeric Constituents as a New Class of Catalyst Support
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Mn(III)-porphyrin containing #heterogeneous catalyst based on microporous polymeric constituents as a new class of #catalyst support from Korea University and Seoul National University of Science and Technology.
- Yi, Jigyoung,Jeong, Ha Young,Shin, Dae Yong,Kim, Cheal,Lee, Suk Joong
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p. 3974 - 3977
(2018/09/25)
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- Catalysis of alkene epoxidation by manganese(II) and (III) complexes of both Schiff base and reduced Schiff base ligands utilizing environmentally benign H2O2
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Mono and disubstituted tridentate Schiff base ligands were synthesized from the reaction of 2(2-aminoethyl)pyridine with 5-bromosalicylaldehyde (H-L1) and 3,5-dibromosalicylaldehyde (H-L2) respectively, which were subsequently reacte
- Egekenze, Rita,Gultneh, Yilma,Butcher, Ray
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p. 198 - 209
(2018/02/15)
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- Non-Heme Iron Catalysts for Olefin Epoxidation: Conformationally Rigid Aryl–Aryl Junction To Support Amine/Imine Multidentate Ligands
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Atom-transfer chemistry represents an important class of reactions catalyzed by metalloenzymes. As a functional mimic of non-heme iron enzymes that deliver oxygen atoms to olefins, we have designed monoiron complexes supported by new N-donor chelates. These ligands take advantage of heme-like conformational rigidity of the π-conjugated molecular backbone, and synthetic flexibility of tethering non-heme donor groups for additional steric and electronic control. Iron complexes generated in situ can be used to carry out catalytic epoxidation of a wide range of olefin substrates by using mCPBA as a terminal oxidant. The fate of initial iron-peracid adduct and the involvement of iron-oxo species in this process were investigated further by mechanistic probes and isotope exchange studies. Our findings suggest that anilidopyridyl-derived [N,N]-bidentate motif could serve as a versatile structural platform to build non-heme ligands for catalytic oxidation chemistry.
- Park, Hyunchang,Ahn, Hye Mi,Jeong, Ha Young,Kim, Cheal,Lee, Dongwhan
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supporting information
p. 8632 - 8638
(2018/05/30)
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- Copper based coordination polymers based on metalloligands: Utilization as heterogeneous oxidation catalysts
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This work presents the synthesis and characterization of two Cu(ii)-based coordination polymers prepared by utilizing two different Co(iii)-based metalloligands offering appended arylcarboxylic acid groups. Both coordination polymers are three-dimensional in nature and present pores and channels filled with water molecules. Both coordination polymers function as heterogeneous catalysts for the epoxidation of various olefins using O2 while employing isobutyraldehyde as the coreductor and for peroxide-mediated oxidation of assorted benzyl alcohols. The catalytic results illustrate efficient oxidation reactions, whereas the hot-fltration test and leaching experiments indicate the true heterogeneous nature of the catalysis.
- Kumar, Gulshan,Hussain, Firasat,Gupta, Rajeev
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p. 16985 - 16994
(2019/01/03)
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- Two-fold interpenetrating btc based cobaltous coordination polymer: A promising catalyst for solvent free oxidation of 1-hexene
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This work describes the synthesis of a new 2-D coordination polymer (CP), [Co3(btc)2(dmp)8]n (btc = 1,3,5-benzenetricarboxylate and dmp = 3,5-dimethylpyrazole) and its catalytic activity towards the oxidation reaction of 1-hexene to form oxygenated compounds under solvent free condition. Structural analysis reveals that Co(II) cations in this polymeric compound are linked by btc3- anions with alternate tetrahedral/octahedral coordination forming a two-fold interpenetrated 3-connected hcb underlying net. Electronic spectrum of the cobaltous polymer has been calculated using TDDFT/B3LYP method for making the appropriate assignments of electronic transitions. Catalytic results show good conversions of the starting material to oxygenated products with high selectivities for 1,2-epoxyhexane and 1-hexanal.
- Bora, Sanchay J.,Paul, Rima,Nandi, Mithun,Bhattacharyya, Pradip K.
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- Co(II) Schiff base complex decorated on polysalicylaldehyde as an efficient, selective, heterogeneous and reusable catalyst for epoxidation of olefins in mild and self-coreductant conditions
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Abstract: A new Co(II)-Schiff base complex was decorated on a polysalicylaldehyde (PSA) framework and used as a selective and efficient catalyst for the epoxidation of alkenes in the presence of O2 as a green source of oxygen without aco-reductant. The catalyst was characterized step by step by FTIR, UV–Vis, 1H NMR, TGA, CHN, XPS and EDX analyses. Loading an amount of Co ions in the catalyst as well as its leaching amount were studied by an ICP-OES instrument. The catalyst demonstrated excellent activity for the of a variety of alkenes in a mild, inexpensive and efficient protocol. Also, the catalyst can be simply recovered from the reaction mixture and reused for several times without any noteiceable loss in its activity. Reaction parameters including temperature, oxygen flow volume, catalyst amount and solvent were screened by reaction time. Catalytic studies including XPS spectroscopy and some blank experiments were performed to obtain an initial insight into the reaction mechanism. Also, the reactivity of the novel catalyst was evaluated as the turnover frequency. Graphical Abstract: A new and efficient protocol have been developed for the selective epoxidation of olefins using a heterogeneous recyclable Co(II)-Schiff base complex of polysalicylaldehyde in mild and self-coreductant conditions by molecular oxygen.
- Kazemnejadi, Milad,Shakeri, Alireza,Nikookar, Mahsa,Mohammadi, Mohammad,Esmaeilpour, Mohsen
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p. 6889 - 6910
(2017/10/05)
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- Cubane cluster type catalyst, synthesizing method of the same and epoxidation of olefin using of the same
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The present invention relates to a cubane cluster type catalyst, a synthesizing method thereof, and an epoxidation method of olefin using the same, and more specifically, to a cobalt metal complex used as a catalyst of an oxidation reaction of hydrocarbon, a synthesizing method thereof, and an epoxidation method of olefin using the same. The epoxidation method of olefin according to one embodiment of the present invention comprises the steps of: (a) synthesizing (S10) a cobalt complex compound in a cubane cluster type; (b) using the cubane cluster type cobalt complex compound as a catalyst and for a solvent having 1:1 of a volume ratio of acetonitrile (CH_3CN) and methylene chloride (CH_2Cl_2), using olefin as a substrate and adding (S20) meta-Chloroperoxybenzoic (mCPBA) acid, an oxidant; and (c) performing an epoxidation reaction at a room temperature. The purpose of the present invention is to provide a cubane cluster type catalyst, a synthesizing method thereof, and an epoxidation method of olefin using the same which can replace a role of metal enzymes playing a catalyst role in oxidation reactions, and in oxidation reactions of various organic substrates, has an excellent catalytic activation without a high temperature and a high pressure and can be used in organic synthesis which is commercially used.COPYRIGHT KIPO 2017
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Paragraph 0037-0040
(2018/03/23)
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- Dinuclear Iron(III) and Nickel(II) Complexes Containing N-(2-Pyridylmethyl)-N′-(2-hydroxyethyl)ethylenediamine: Catalytic Oxidation and Magnetic Properties
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Dinuclear FeIII and NiII complexes, [(phenO)Fe(N3)]2(NO3)2 (1) and [(phenOH)Ni(N3)2]2 (2), were prepared by treating Fe(NO3)3?9 H2O and Ni(NO3)2?6 H2O in methanol, respectively, with phenOH (=N-(2-pyridylmethyl)-N′-(2-hydroxyethyl)ethylenediamine) and NaN3; both 1 and 2 were characterized by elemental analysis, IR spectroscopy, X-ray diffraction, and magnetic susceptibility measurements. Two ethoxo-bridged FeIII and two azido-bridged NiII were observed in 1 and 2, respectively; corresponding antiferromagnetic interaction via the bridged ethoxo groups and strong ferromagnetic coupling via the bridged end-on azido ligands within the dimeric unit were observed. Complex 1 did not exhibit any catalytic activity, while 2 exhibited excellent catalytic activities for the epoxidation of aliphatic, aromatic, and terminal olefins.
- Jeong, Ah Rim,Shin, Jong Won,Jeong, Jong Hwa,Bok, Kwon Hee,Kim, Cheal,Jeong, Donghyun,Cho, Jaeheung,Hayami, Shinya,Min, Kil Sik
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p. 3023 - 3033
(2017/03/13)
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- Synthesis, Characterization, and Catalytic Activities of A Nickel(II) Monoamido-Tetradentate Complex: Evidence For NiIII–Oxo and NiIV–Oxo Species
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A new mononuclear nickel(II) complex, [NiII(dpaq)Cl] (1), containing a tetradentate monoamido ligand, dpaq (dpaq=2-[bis(pyridin-2-ylmethyl)amino]-N-(quinolin-8-yl)acetamide), has been synthesized and characterized by IR spectroscopy, elemental analysis, and UV/Vis spectroscopy. The structure of the nickel complex has been determined by X-ray crystallography. This nonheme NiII complex 1 catalyzed the epoxidation reaction of a wide range of olefins with meta-chloroperoxybenzoic acid (m-CPBA) under mild conditions. Olefin epoxidation using this catalytic system has been proposed to involve a new reactive NiIV–oxo (4) species, based on the evidence from a PPAA (peroxyphenylacetic acid) probe, Hammett studies, H218O exchange experiments, and ESI mass spectroscopic analysis. Moreover, the nature of solvent significantly influenced partitioning between heterolytic and homolytic O?O bond cleavage of the Ni–acylperoxo intermediate (2). The O?O bond of 2 proceeded predominantly through heterolytic cleavage in a protic solvent, such as CH3OH. These results suggest that possibly a NiIV–oxo species is a common reactive intermediate in protic solvents. The two active oxidants, namely NiIV–oxo (3) and NiIII–oxo (4), which are responsible for stereospecific olefin epoxidation and radical-type oxidations, respectively, operate in aprotic solvents.
- Bok, Kwon Hee,Lee, Myoung Mi,You, Ga Rim,Ahn, Hye Mi,Ryu, Ka Young,Kim, Sung-Jin,Kim, Youngmee,Kim, Cheal
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p. 3117 - 3125
(2017/03/14)
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- Synthesis, Characterization, and Efficient Catalytic Activities of a Nickel(II) Porphyrin: Remarkable Solvent and Substrate Effects on Participation of Multiple Active Oxidants
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A new nickel(II) porphyrin complex, [NiII(porp)] (1), has been synthesized and characterized by 1H NMR, 13C NMR and mass spectrometry analysis. This NiII porphyrin complex 1 quantitatively catalyzed the epoxidation reaction of a wide range of olefins with meta-chloroperoxybenzoic acid (m-CPBA) under mild conditions. Reactivity and Hammett studies, H218O-exchange experiments, and the use of PPAA (peroxyphenylacetic acid) as a mechanistic probe suggested that participation of multiple active oxidants NiII?OOC(O)R 2, NiIV-Oxo 3, and NiIII-Oxo 4 within olefin epoxidation reactions by the nickel porphyrin complex is markedly affected by solvent polarity, concentration, and type of substrate. In aprotic solvent systems, such as toluene, CH2Cl2, and CH3CN, multiple oxidants, NiII?(O)R 2, NiIV-Oxo 3, and NiIII-Oxo 4, operate simultaneously as the key active intermediates responsible for epoxidation reactions of easy-to-oxidize substrate cyclohexene, whereas NiIV-Oxo 3 and NiIII-Oxo 4 species become the common reactive oxidant for the difficult-to-oxidize substrate 1-octene. In a protic solvent system, a mixture of CH3CN and H2O (95:5), the NiII?OOC(O)R 2 undergoes heterolytic or homolytic O?O bond cleavage to afford NiIV-Oxo 3 and NiIII-Oxo 4 species by general acid catalysis prior to direct interaction between 2 and olefin, regardless of the type of substrate. In this case, only NiIV-Oxo 3 and NiIII-Oxo 4 species were the common reactive oxidant responsible for olefin epoxidation reactions.
- Ahn, Hye Mi,Bae, Jeong Mi,Kim, Min Jeong,Bok, Kwon Hee,Jeong, Ha Young,Lee, Suk Joong,Kim, Cheal
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p. 11969 - 11976
(2017/09/07)
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- Activated vs. pyrolytic carbon as support matrix for chemical functionalization: Efficient heterogeneous non-heme Mn(II) catalysts for alkene oxidation with H2O2
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Two types of heterogeneous catalytic materials, MnII-L3imid@Cox and MnII-L3imid@PCox, have been synthesized and compared by covalent grafting of a catalytically active [MnII-L3imid] complex on the surface of an oxidized activated carbon (Cox) and an oxidized pyrolytic carbon from recycled-tire char (PCox). Both hybrids are non-porous bearing graphitic layers intermixed with disordered sp2/sp3 carbon units. Raman spectra show that (ID/IG)activatedcarbon > (ID/IG)pyrolyticcarbon revealing that oxidized activated carbon(Cox) is less graphitized than oxidized pyrolytic carbon (PCox). The MnII-L3imid@Cox and MnII-L3imid@PCox catalysts were evaluated for alkene oxidation with H2O2 in the presence of CH3COONH4. Both showed high selectivity towards epoxides and comparing the achieved yields and TONs, they appear equivalent. However, MnII-L3imid@PCox catalyst is kinetically faster than the MnII-L3imid@Cox (accomplishing the catalytic runs in 1.5 h vs. 5 h). Thus, despite the similarity in TONs MnII-L3imid@PCox achieved extremely higher TOFs vs. MnII-L3imid@Cox. Intriguingly, in terms of recyclability, MnII-L3imid@Cox could be reused for a 2th run showing a ~20% loss of its catalytic activity, while MnII-L3imid@PCox practically no recyclable. This phenomenon is discussed in a mechanistic context; interlinking oxidative destruction of the Mn-complex with high TOFs for MnII-L3imid@PCox, while the low-TOFs of MnII-L3imid@Cox are preventive for the oxidative destruction of the Mn-complex.
- Simaioforidou,Papastergiou,Margellou,Petrakis,Louloudi
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p. 516 - 525
(2016/12/16)
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- Asymmetric Hydrolytic and Aminolytic Kinetic Resolution of Racemic Epoxides using Recyclable Macrocyclic Chiral Cobalt(III) Salen Complexes
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New chiral macrocyclic cobalt(III) salen complexes were synthesized and used as catalyst for the asymmetric kinetic resolution (AKR) of terminal epoxides and glycidyl ethers with aromatic/aliphatic amines and water as nucleophiles. This is the first occasion where a Co(III) salen complex demonstrated its ability to catalyze AKR as well as hydrolytic kinetic resolution (HKR) reactions. Excellent enantiomeric excesses of the epoxides, the corresponding amino alcohols and diols (upto 99%) with quantitative yields were achieved by using the chiral Co(III) salen complexes in dichloromethane at room temperature. This protocol was further extended for the synthesis of two important drug molecules, i.e., (S)-propranolol and (R)-naftopidil. The catalytic system was also explored for the synthesis of chirally pure diols and chiral cyclic carbonates using carbon dioxide as a greener renewable C1 source. The catalyst was recycled for upto 5 catalytic cycles with retention of enantioselectivity. (Figure presented.).
- Tak, Rajkumar,Kumar, Manish,Menapara, Tusharkumar,Gupta, Naveen,Kureshy, Rukhsana I.,Khan, Noor-ul H.,Suresh
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supporting information
p. 3990 - 4001
(2017/11/22)
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- Production Of Enantiopure alpha-Hydroxy Carboxylic Acids From Alkenes By Cascade Biocatalysis
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The invention provides compositions comprising an alkene epoxidase and a selective epoxide hydrolase, such as a recombinant microorganism comprising a first heterologous nucleic acid encoding an alkene epoxidase and a second heterologous nucleic acid encoding a selective epoxide hydrolase. Exemplary alkene epoxidases include StyAB, while exemplary selective epoxide hydrolases include epoxide hydrolases from Sphingomonas, Solanum tuberosum, or Aspergillus. The invention also provides non-toxic methods of making enantiomerically pure vicinal diols or enantiomerically pure alpha-hydroxy carboxylic acids using these compositions and microorganisms.
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Paragraph 0103; 0104
(2016/05/02)
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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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- Heterometallic Metal-Organic Frameworks That Catalyze Two Different Reactions Sequentially
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A series of copper- and alkaline-earth-metal-based multidimensional metal-organic frameworks, {[CuMg(pdc)2(H2O)4]·2H2O}n (1), [CuCa(pdc)2]n (2), [CuSr(pdc)2(H2O)3]n (3), and {[Cuba(pdc)2(H2O)5]·H2O}n (4), where H2Pdc = pyridine-2,5-dicarboxylic acid, were hydrothermally synthesized and characterized. Two different metals act as the active center to catalyze two kinds of reactions, viz., olefin to its epoxide followed by epoxide ring opening to afford the corresponding vicinal diol in a sequential manner.
- Saha, Debraj,Hazra, Dipak K.,Maity, Tanmoy,Koner, Subratanath
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supporting information
p. 5729 - 5731
(2016/07/06)
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- Trinuclear nickel and cobalt complexes containing unsymmetrical tripodal tetradentate ligands: Syntheses, structural, magnetic, and catalytic properties
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The coordination chemistries of the tetradentate N2O2-type ligands N-(2-pyridylmethyl)iminodiethanol (H2pmide) and N-(2-pyridylmethyl)iminodiisopropanol (H2pmidip) have been investigated with nickel(ii) and cobalt(ii/iii) ions. Three novel complexes prepared and characterized are [(Hpmide)2Ni3(CH3COO)4] (1), [(Hpmide)2Co3(CH3COO)4] (2), and [(pmidip)2Co3(CH3COO)4] (3). In 1 and 2, two terminal nickel(ii)/cobalt(ii) units are coordinated to one Hpmide- and two CH3CO2-. The terminal units are each connected to a central nickel(ii)/cobalt(ii) cation through one oxygen atom of Hpmide- and two oxygen atoms of acetate ions, giving rise to nickel(ii) and cobalt(ii) trinuclear complexes, respectively. Trinuclear complexes 1 and 2 are isomorphous. In 3, two terminal cobalt(iii) units are coordinated to pmidip2- and two CH3CO2-. The terminal units are each linked to a central cobalt(ii) cation through two oxygen atoms of pmidip2- and one oxygen atom of a bidentate acetate ion, resulting in a linear trinuclear mixed-valence cobalt complex. 1 shows a weak ferromagnetic interaction with the ethoxo and acetato groups between the nickel(ii) ions (g = 2.24, J = 2.35 cm-1). However, 2 indicates a weak antiferromagnetic coupling with the ethoxo and acetato groups between the cobalt(ii) ions (g = 2.37, J = -0.5 cm-1). Additionally, 3 behaves as a paramagnetic cobalt(ii) monomer, due to the diamagnetic cobalt(iii) ions in the terminal units (g = 2.53, =D= = 36.0 cm-1). No catalytic activity was observed in 1. However, 2 and 3 showed significant catalytic activities toward various olefins with modest to good yields. 3 was slightly less efficient toward olefin epoxidation reaction than 2. Also 2 was used for terminal olefin oxidation reaction and was oxidised to the corresponding epoxides in moderate yields (34-75%) with conversions ranging from 47-100%. The cobalt complexes 2 and 3 promoted the O-O bond cleavage to ~75% heterolysis and ~25% homolysis.
- Shin, Jong Won,Jeong, Ah Rim,Lee, Sun Young,Kim, Cheal,Hayami, Shinya,Min, Kil Sik
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p. 14089 - 14100
(2016/11/06)
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- POSS-derived mesoporous ionic copolymer-polyoxometalate catalysts with a surfactant function for epoxidation reactions
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A series of novel polyoxometalate (POM)-based stable polymeric hybrids were successfully synthesized using polyhedral oligomeric vinylsilsesquioxanes (POSS) and ionic liquids (IL) bearing hydrophobic alkyl chains as the building blocks, followed by ion exchange with Keggin-type phosphotungstic acid (PW). The obtained hybrids POSS-ILx-PW were demonstrated to be mesostructured and amphiphilic materials with good thermal stability. Catalytic tests for the H2O2-based epoxidation of cyclooctene have shown that these newly designed catalysts exhibit extraordinary catalytic activities, catalytic rates, and quite stable reusability. The unique amphiphilic property and the mesoporous structure are revealed to be responsible for the catalysts' excellent performance in epoxidation reactions with H2O2.
- Zhao, Jiwei,Leng, Yan,Jiang, Pingping,Wang, Jun,Zhang, Chenjun
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p. 1022 - 1028
(2016/02/19)
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- Design and synthesis of nanoporous perylene bis-imide linked metalloporphyrin frameworks and their catalytic activity
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Two nanoporous perylene bis-imide linked metalloporphyrin framework catalysts have been synthesized via condensation of 5,10,15,20-tetrakis-(4 ′ -aminophenyl) iron(III) porphyrin chloride or 5,10, 15,20-tetrakis-(4 ′ -aminophenyl) manganese(III) porphyrin chloride with perylene-3,4,9,10-tetracarboxylic dianhydride. Both the materials were crystalline in nature and were characterized by electron microscopy techniques, solid-state 1H- 13C CP/MS NMR, powder X-ray diffraction (PXRD), and magnetic susceptibility measurements. The nitrogen gas physisorption study has indicated that both materials are porous in nature and have BET surface area with 653 m2/g and 974 m2/g with uniform pore size of 2.8 nm. These materials were found to act as very good heterogeneous catalysts for selective oxidation of alkanes and alkenes with tert-butyl hydroperoxide and were not degraded even after multiple uses up to 10 cycles.
- Singh, Manoj Kumar,Bandyopadhyay, Debkumar
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- Cation-exchange resin towards low-cost synthesis of high-performance TS-1 zeolites in the presence of alkali-metal ions
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Zeolite TS-1 is an important commercial catalyst for green production of oxyfunctionalized chemicals such as alcohols, ketones, epoxides, and oximes. However, the extremely high price greatly restricts its wide applications. In this paper, we developed a new route to synthesize highly active TS-1 zeolites by using low-cost tetrapropylammonium hydroxide (TPAOH) as a starting reagent that contains alkali-metal cations such as Na+ and K+ and is much cheaper than the high-purity TPAOH currently used in reported routes. The key point is the introduction of a cation-exchange resin into the synthetic system to capture the alkali-metal cations via ion exchange between the alkali-metal cations in the synthetic medium and protons in the resin, as well as adjusting the pH value of the TS-1 synthetic system. The present development shows great commercial potential and opens the possibility of preparing cheap TS-1 catalysts by using commercial TPAOH raw materials.
- Wang, Jin-Gui,Wang, Yabo,Chen, Hongzhong,Lim, Jiesheng,Tatsumi, Takashi,Zhao, Yanli
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p. 15615 - 15621
(2016/02/26)
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- Application of homochiral alkylated organic cages as chiral stationary phases for molecular separations by capillary gas chromatography
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Molecular organic cage compounds have attracted considerable attention due to their potential applications in gas storage, catalysis, chemical sensing, molecular separations, etc. In this study, a homochiral pentyl cage compound was synthesized from a condensation reaction of (S,S)-1,2-pentyl-1,2-diaminoethane and 1,3,5-triformylbenzene. The imine-linked pentyl cage diluted with a polysiloxane (OV-1701) was explored as a novel stationary phase for high-resolution gas chromatographic separation of organic compounds. Some positional isomers were baseline separated on the pentyl cage-coated capillary column. In particular, various types of enantiomers including chiral alcohols, esters, ethers and epoxides can be resolved without derivatization on the pentyl cage-coated capillary column. The reproducibility of the pentyl cage-coated capillary column for separation was investigated using nitrochlorobenzene and styrene oxide as analytes. The results indicate that the column has good stability and separation reproducibility after being repeatedly used. This work demonstrates that molecular organic cage compounds could become a novel class of chiral separation media in the near future.
- Xie, Shengming,Zhang, Junhui,Fu, Nan,Wang, Bangjin,Hu, Cong,Yuan, Liming
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- The Activation of Carboxylic Acids via Self-Assembly Asymmetric Organocatalysis: A Combined Experimental and Computational Investigation
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The heterodimerizing self-assembly between a phosphoric acid catalyst and a carboxylic acid has recently been established as a new activation mode in Br?nsted acid catalysis. In this article, we present a comprehensive mechanistic investigation on this activation principle, which eventually led to its elucidation. Detailed studies are reported, including computational investigations on the supramolecular heterodimer, kinetic studies on the catalytic cycle, and a thorough analysis of transition states by DFT calculations for the rationalization of the catalyst structure-selectivity relationship. On the basis of these investigations, we developed a kinetic resolution of racemic epoxides, which proceeds with high selectivity (up to s = 93), giving the unreacted epoxides and the corresponding protected 1,2-diols in high enantiopurity. Moreover, this approach could be advanced to an unprecedented stereodivergent resolution of racemic α-chiral carboxylic acids, thus providing access to a variety of enantiopure nonsteroidal anti-inflammatory drugs and to α-amino acid derivatives.
- Monaco, Mattia Riccardo,Fazzi, Daniele,Tsuji, Nobuya,Leutzsch, Markus,Liao, Saihu,Thiel, Walter,List, Benjamin
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supporting information
p. 14740 - 14749
(2016/11/18)
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- Azidolysis of epoxides catalysed by the halohydrin dehalogenase from Arthrobacter sp. AD2 and a mutant with enhanced enantioselectivity: an (S)-selective HHDH
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Halohydrin dehalogenase from Arthrobacter sp. AD2 catalysed azidolysis of epoxides with high regioselectivity and low to moderate (S)-enantioselectivity (E?=?1–16). Mutation of the asparagine 178 to alanine (N178A) showed increased enantioselectivity towards styrene oxide derivatives and glycidyl ethers. Conversion of aromatic epoxides was catalysed by HheA-N178A with complete enantioselectivity, however the regioselectivity was reduced. As a result of the enzyme-catalysed reaction, enantiomerically pure (S)-β-azido alcohols and (R)-α-azido alcohols (ee???99%) were obtained.
- Mikleu?evi?, Ana,Primo?i?, Ines,Hrenar, Tomica,Salopek-Sondi, Branka,Tang, Lixia,Elenkov, Maja Majeri?
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p. 930 - 935
(2016/09/13)
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- Titanium cis-1,2-diaminocyclohexane (cis-DACH) salalen catalysts for the asymmetric epoxidation of terminal non-conjugated olefins with hydrogen peroxide
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Chiral Ti salalen complexes catalyze the asymmetric epoxidation of terminal non-conjugated olefins with hydrogen peroxide. Modular ligands based on cis-1,2-diaminocyclohexane (cis-DACH) were developed, giving high yields and enantiomeric excesses (ee, up to 96%) at catalyst loadings as low as 0.1-0.5mol%, and even under solvent-free conditions.
- Wang, Qifang,Neud?rfl, J?rg-M.,Berkessel, Albrecht
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p. 247 - 254
(2015/07/07)
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