- Urea-hydrogen peroxide/hexafluoro-2-propanol: An efficient system for a catalytic epoxidation reaction without a metal
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Hexafluoro-2-propanol (HFIP) exhibits a unique ability to release and activate H2O2 from the urea-hydrogen peroxide adduct (UHP). This UHP/HFIP system was investigated in epoxidation of olefins, using various fluoroketones as catalysts. With reactive olefins, no catalyst was required. With monosubstituted olefins, epoxides were obtained in high yields by using catalytic amounts (3-5%) of perfluorodecan-2-one. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Legros, Julien,Crousse, Benoit,Bonnet-Delpon, Daniele,Begue, Jean-Pierre
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- Development of a lipase-mediated epoxidation process for monoterpenes in choline chloride-based deep eutectic solvents
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Chemical syntheses in contemporary process industries today are predominantly conducted using organic solvents, which are potentially hazardous to humans and the environment alike. Green chemistry was developed as a means to overcome this hazard and it also holds enormous potential for designing clean, safe and sustainable processes. The present work incorporates the concepts of green chemistry in its design of a lipase-mediated epoxidation process for monoterpenes; the process uses alternative reaction media, namely deep eutectic solvents (DESs), which have not been reported for such an application before. Choline chloride (ChCl), in combination with a variety of hydrogen bond donors (HBD) at certain molar ratios, was screened and tested for this purpose. The process was optimized through the design of experiments (DoE) using the Taguchi method for four controllable parameters (temperature, enzyme amount, peroxide amount and type of substrate) and one uncontrollable parameter (DES reaction media) in a crossed-array design. Two distinct DESs, namely glycerol:choline chloride (GlCh) and sorbitol:choline chloride (SoCh), were found to be the best systems and they resulted in a complete conversion of the substrates within 8 h. Impurities (esters) were found to form in both the DESs, which was a concern; as such, we developed a novel minimal DES system that incorporated a co-substrate into the DES so that this issue could be overcome. The minimal DES consisted of urea·H2O2 (U·H2O2) and ChCl and exhibited better results than both the GlCh and SoCh systems; complete conversions were achieved within 2 h for 3-carene and within 3 h for both limonene and α-pinene. Product isolation with a simple water/ethyl acetate based procedure gave isolated yields of 87.2 ± 2.4%, 77.0 ± 5.0% and 84.6 ± 3.7% for 3-carene, limonene and α-pinene respectively.
- Ranganathan, Sumanth,Zeitlhofer, Sandra,Sieber, Volker
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- Controlling Selectivity in Alkene Oxidation: Anion Driven Epoxidation or Dihydroxylation Catalysed by [Iron(III)(Pyridine-Containing Ligand)] Complexes
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A highly reactive and selective catalytic system comprising Fe(III) and macrocyclic pyridine-containing ligands (Pc-L) for alkene oxidation by using hydrogen peroxide is reported herein. Four new stable iron(III) complexes have been isolated and characterized. Importantly, depending on the anion of the iron(III) metal complex employed as catalyst, a completely reversed selectivity was observed. When X=OTf, a selective dihydroxylation reaction took place. On the other hand, employing X=Cl resulted in the epoxide as the major product. The reaction proved to be quite general, tolerating aromatic and aliphatic alkenes as well as internal or terminal double bonds and both epoxides and diol products were obtained in good yields with good to excellent selectivities (up to 93 % isolated yield and d.r.=99 : 1). The catalytic system proved its robustness by performing several catalytic cycles, without observing catalyst deactivation. The use of acetone as a solvent and hydrogen peroxide as terminal oxidant renders this catalytic system appealing.
- Tseberlidis, Giorgio,Demonti, Luca,Pirovano, Valentina,Scavini, Marco,Cappelli, Serena,Rizzato, Silvia,Vicente, Rubén,Caselli, Alessandro
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p. 4907 - 4915
(2019/08/30)
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- Syntheses and catalytic activities of new metallodendritic catalysts
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This investigation presents the syntheses of new metallodendritic catalysts from a silsesquioxane core (Silsesq-PrNH3+Cl-) via a new route. For optimization of the syntheses of the catalysts, reaction times, thermodynamic effects, and the amounts of [Mo(η3-C3H5)Br(CO)2(NCCH3)2] (1) and [Mo(CO)3Br2(NCCH3)2] (2) complexes fixed on the second-generation dendrimer (PDG2.0) were studied. After the optimization studies and with the objective of application in catalysis, the catalysts were prepared by reaction of PDG2.0 with the organometallic complexes and characterized by elemental analysis (CNH), FTIR, 13C and 29Si NMR, XRD, TGA, SEM, EDS and BET. The metallodendritic catalysts were tested in the epoxidation of olefins and shown to be a vigorous catalyst with conversion rates between 76 and 97% for PDG2.0-[(Mo(η3-C3H5)(CO)2Br)8] and 30-80% for PDG2.0-[(Mo(CO)3Br2)5], and a high selectivity in the formation of epoxides using tertbutyl hydroperoxide (TBHP) as an oxidant. The catalysts remain highly active after being used for at least 5 cycles. To the best of our knowledge, this study is the first to have reported the preparation of these new dendritic catalysts, as well as the catalytic comparison with their previous generations in the epoxidation of 1-octene, cyclooctene, (S)-limonene, cis-3-hexen-1-ol, trans-3-hexen-1-ol and styrene.
- Vieira, Eduardo Guimar?es,Silva, Rafael Oliveira,Dal-Bó, Alexandre Gon?alves,Frizon, Tiago Elias Allievi,Filho, Newton Luiz Dias
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p. 9403 - 9414
(2016/11/09)
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- Grafted non-ordered niobium-silica materials: Versatile catalysts for the selective epoxidation of various unsaturated fine chemicals
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Two kinds of niobium(V)-silica catalysts for the selective epoxidation were synthesised by post-synthesis modification of non-ordered mesoporous silica supports, starting from niobocene dichloride via solvent-less organometallic precursor dry impregnation
- Tiozzo, Cristina,Bisio, Chiara,Carniato, Fabio,Guidotti, Matteo
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- Use of titanium-containing silica catalysts prepared by rapid and straightforward method in selective oxidations
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A series of titanium-containing silica catalysts (Ti4/SiO 2) with small oligomeric Ti centres is obtained by impregnation of the air-stable and water-soluble tetranuclear Ti complex (NH4) 8[Ti4(C6H4O7) 4(O2)4]·8H2O onto commercial non-ordered mesoporous silica supports. Catalyst preparation is performed under very mild conditions, with no controlled atmosphere, following a simple, cheap, safe and sustainable methodology. Ti4/SiO2 catalysts can be used in the presence of TBHP or aqueous hydrogen peroxide and were tested in the selective oxidation of limonene, cyclohexene, trans-stilbene and 2,3,6-trimethylphenol. These catalysts showed performances fully comparable to (or even better than) those obtained with titanium-silicate materials prepared via conventional post-synthesis grafting approaches from organometallic precursors.
- Pirovano,Guidotti,Dal Santo,Psaro,Kholdeeva,Ivanchikova
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p. 170 - 177
(2013/01/15)
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- Iron(III) porphyrin covalently supported onto magnetic amino-functionalized nanospheres as catalyst for hydrocarbon and herbicide oxidations
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This work describes the covalent immobilization of an ironporphyrin, 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin iron(III) chloride (FeTFPP), onto maghemite/silica magnetic nanospheres covered with aminofunctionalized silica. The resulting material (γ-Fe2O3/SiO 2-NHFeP) was characterized by diffuse reflectance infrared spectroscopy (DRIFTS) and UV-Vis absorption spectroscopy. The catalytic activity of this magnetic ironporphyrin was investigated in the oxidation of hydrocarbons (styrene, (Z)-cyclooctene and R-(+)-limonene) and an herbicide (simazine) by hydrogen peroxide or 3-chloroperoxybenzoic acid. Hydrocarbon and simazine oxidation reaction products were analyzed by gas chromatography (GC) and high performance liquid chromatography (HPLC), respectively. This catalytic system proved to be efficient and selective for hydrocarbon oxidation, leading to high product yields from styrene (89percent), cyclooctene (71percent) and R-(+)-limonene (86percent). Simazine oxidation was attained with 100percent selectivity for a dechlorinated product (OEAT), while several oxidation products were obtained for the same catalyst in homogeneous media. The catalyst can be easily recovered through application of an external magnetic field and washed after reaction. Catalyst reuse experiments for R-(+)-limonene oxidation have shown that the catalytic activity is kept at 90percent after 10 consecutive reactions. ?2012 Sociedade Brasileira de Qui?mica.
- Dos Santos, Joicy S.,Faria, Andre? L.,Da Silva Amorin, Patri?cia M.,La Luna, Franco M.,Caiado, Kely L.,E Silva, De?bora O.C.,Sartoratto, Patri?cia P.C.,Assis, Marilda D.
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p. 1411 - 1420
(2012/11/13)
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- Efficient, regioselective epoxidation of dienes with hydrogen peroxide catalyzed by [γ-SiW10O34(H2O) 2]4-
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A divacant, lacunary, Keggin-type silicotungstate, [γ-SiW 10O34(H2O)2]4-, exhibits high catalytic performance for the epoxidation of various nonconjugated dienes using hydrogen peroxide under mild conditions, high regioselectivity to the more accessible double bonds, and high efficiency of hydrogen peroxide utilization. The high regioselectivity for the [γ-SiW10O34(H 2O)2]4--catalyzed epoxidation would be caused by the steric hindrance of the active site.
- Kamata, Keigo,Nakagawa, Yoshinao,Yamaguchi, Kazuya,Mizuno, Noritaka
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p. 224 - 228
(2007/10/03)
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- A cyclodextrin-modified ketoester for stereoselective epoxidation of alkenes
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A β-cyclodextrin-modified ketoester 2 was prepared by covalent attachment of a reactive ketone moiety to β-cyclodextrin. Treatment of 2 with Oxone as terminal oxidant would produce CD-substituted dioxirane, which can effect stereoselective alkene epoxidation. The 2-mediated (S)-α-terpineol epoxidations proceeded to give terpineol oxides in high yields, and the stereoselectivities (i.e., cis-/trans-epoxide ratio) decreased from 2.5:1 to 1:1.2 with increasing steric bulkiness of the terpenes. This steric-dependent stereoselectivity can be understood based on different binding geometries of the 2/terpene inclusion complexes according to the 1H NMR titration and 2D ROESY experiments. Enantioselective epoxidation of styrenes has also been achieved with 2 as catalyst (20-50 mol %) in aqueous acetonitrile solution, and up to 40% ee was obtained in 4-chlorostyrene epoxidation at 0 °C. Similar enantioselectivities were also obtained for the 2-mediated epoxidation of 1,2-dihydronaphthalene (37% ee), 4-chlorostyrene (36% ee), and trans-stilbene (31% ee).
- Chan, Wing-Kei,Yu, Wing-Yiu,Che, Chi-Ming,Wong, Man-Kin
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p. 6576 - 6582
(2007/10/03)
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- Studies on olefin epoxidation with t-BuOOH catalysed by dioxomolybdenum(VI) complexes of a novel chiral pyridyl alcoholate ligand
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The chiral dioxomolybdenum(VI) complexes [MoCl{(1R,2S,5S)-8-trimethylsilyloxy-1-(2-pyridyl)mentholato}(O)2 (THF)] and [Mo{(1R,2S,5S)-8-trimethylsilyloxy-1-(2-pyridyl)mentholato}2(O) 2] have been prepared in good yields by reaction of the solvent substituted complex [MoCl2O2(THF)2] with one or two equivalents of chiral 2′-pyridyl alcohol. The optically active aminoalcohol was obtained by reaction of 2-pyridyllithium with (-)-(2S,5S)-8-trimethylsilyloxymenthone. The complexes are active catalysts in the homogeneous epoxidation of cyclic and linear olefins, dienes and terpenes by t-BuOOH. They present remarkable activity and excellent product selectivity in cyclooctene epoxidation (cyclooctene oxide was obtained in quantitative yield). In the case of limonene, regioselectivity is high in favour of the epoxidation of the internal cyclic double bond. Ring opening activity was also observed for α-pinene oxide, producing campholenic aldehyde and epoxy campholenic aldehyde.
- Valente,Goncalves,Lopes,Rodriguez-Borges,Pillinger,Romao,Rocha,Garcia-Mera
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p. 959 - 963
(2007/10/03)
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