203719-54-4Relevant articles and documents
Environmentally friendly epoxidation of olefins under phase-transfer catalysis conditions with hydrogen peroxide
Mahha, Yahdih,Salles, Laurent,Piquemal, Jean-Yves,Briot, Emmanuel,Atlamsani, Ahmed,Bregeault, Jean-Marie
, p. 338 - 348 (2007)
Several catalysis systems, WO3sH2O/H2O2 -H2O-H3O+/Q+A-/H3 PO4/H2SO4/solvent (Q+A- = Arquad 2HT, [CH3(n-C8H17)3N]+ Cl-; [CH3(n-C8H17)3N]+ HSO4-, [CH3(n-C8H17)3N]+ H2PO4-; solvent: CHCl3 or toluene) were used to selectively and efficiently convert olefins to their corresponding epoxides at room temperature. With cyclooctene and using Arquad 2HT as the phase-transfer agent, there is a synergy when both phosphate and sulfate anions are present in the reaction medium compared with systems using either one or the other. The importance of the tungsten(VI) source is, as found previously, underlined by the strong activity increase when WO3sH2O is used instead of Na2WO4s2H2O, even at room temperature. The influence of the phase-transfer agent Q+A- has been evaluated for the system WO3sH2O/H2O2 -H2O-H3O+/Q+A-/toluene. With Q+A- (Q+ = [CH3(n-C8H17)3N]+ and A- = Cl-, HSO4-, and H2PO4-), the best results for the conversion of cyclooctene at room temperature are obtained with [CH3(n-C8H17)3N]+ H2PO4-. 31P NMR experiments show the transfer in the organic phase of the [PO4{W2O2(μ-O2) 2(O2)2}2]3- and [HPO4{W2O2(μ-O2) 2(O2)2}]2- complexes with H3PO4 and H2PO4-, whereas only [PO4{W2O2(μ-O2) 2(O2)2}2]3- can be identified with the addition of H3PO4/HSO4- or H2PO4-/H2SO4. Moreover, acid-sensitive epoxides can be prepared using buffers generated by the addition of sodium hydrogenocarbonate or, preferably, disodium hydrogenophosphate, leading to high selectivities toward the corresponding epoxides. The data show that disodium hydrogenophosphate gives the best results even if the reaction time has to be increased to obtain high conversions. The WO3sH2O/H2O2 -H2O/[CH3(n-C8H17) 3N]+H2PO4-/toluene catalysis system can be reused in 5 consecutive runs with no loss in activity.
Catalytic performance of bulk and colloidal Co/Al layered double hydroxide with Au nanoparticles in aerobic olefin oxidation
Leandro, Sónia R.,Fernandes, Cristina I.,Viana,Mourato,Vaz, Pedro D.,Nunes, Carla D.
, (2019/08/07)
A Co/Al layered double hydroxide material was synthesized in both bulk and exfoliated (colloidal) forms. Anion exchange with methionine allowed immobilization of Au nanoparticles previously prepared by a biomimetic method using an anti-oxidant tea aqueous extract to reduce the Au salt solution. The catalytic performance of bulk and exfoliated clays Au-hybrid materials was assessed in aerobic olefin epoxidation. Both catalysts were very active towards the epoxide products and with very interesting substrate conversion levels after 80 h reaction time. The Au-exfoliated material, where the nanosheets work as large ligands, yielded higher product stereoselectivity in the case of limonene epoxidation. This arises from a confined environment around the Au nanoparticles wrapped by the clay nanosheets modulating access to the catalytic active centres by reagents. Mechanistic assessment was also accomplished for styrene oxidation by DFT methods.
Organocatalyzed epoxidation of alkenes in continuous flow using a multi-jet oscillating disk reactor
Spaccini, Raffaele,Liguori, Lucia,Punta, Carlo,Bj?rsvik, Hans-René
scheme or table, p. 261 - 265 (2012/05/05)
The times are changing: A batch process, the Minisci epoxidation, is transformed into a continuous-flow protocol for the selective aerobic radical epoxidation of alkenes. The use of a novel reactor type allows to considerably shorten reactor residence times. Experimental results suggest that two different reaction mechanisms exist for the oxidation: one for the batch conditions and a different one for flow synthesis protocol. Copyright
A Ti-substituted polyoxometalate as a heterogeneous catalyst for olefin epoxidation with aqueous hydrogen peroxide
Hua, Li,Qiao, Yunxiang,Yu, Yinyin,Zhu, Wenwen,Cao, Ting,Shi, Yu,Li, Huan,Feng, Bo,Hou, Zhenshan
experimental part, p. 1836 - 1841 (2011/10/10)
The Ti-substituted polyoxometalates ([C12mim] 5PTiW11O40, [CTA]5PTiW 11O40 and [TBA]5PTiW11O 40) were prepared and characterized by FT-IR, NMR, UV-vis and ICP-AES. Then the polyoxometalates (POM) were used as catalysts for the epoxidation of various olefins. It was found that the organic countercations had a considerable effect on the catalytic performance. In addition, UV-vis and the FT-IR spectroscopy indicated that the peroxo structure regarded as the active site for oxygen transfer was present even after the reaction, which led to the increasing reaction rate in the second run due to the disappearance of the induction period, as compared with that in the first run. A heterogeneous reaction mechanism has been suggested in olefin epoxidation catalyzed by a Ti-substituted polyoxometalate ([C12mim]5PTiW 11O40) with aqueous hydrogen peroxide in ethyl acetate. The heterogeneous POM catalyst can be easily separated and recycled eight times without decreasing the catalytic activities.
Facile methods for the separation of the cis- and trans-diastereomers of limonene 1,2-oxide and convenient routes to diequatorial and diaxial 1,2-diols
Blair, Michael,Andrews, Philip C.,Fraser, Benjamin H.,Forsyth, Craig M.,Junk, Peter C.,Massi, Massimiliano,Tuck, Kellie L.
, p. 1523 - 1527 (2008/02/08)
Facile methods are described for accessing four diastereomerically pure products from the commercial mixture of limonene oxide. The use of either an aqueous mercury(II)-mediated or H+-catalysed hydration, afforded a kinetic separation of (+)-limonene oxide (cis- or trans-isomer could be respectively recovered) from the commercially available diastereomeric mixture in good recovery yields and high diastereoselectivity (>98% de). The hydrolysed limonene oxide products, either trans-diequatorial or trans-diaxial diols, are also formed in good conversion yields and high diastereoselectivity (>98% de). Georg Thieme Verlag Stuttgart.
Interaction of a chirally functionalised porphyrin derivative with chiral micellar aggregates. Construction of a system with stereoselective cytochrome-P450 biomimetic activity
Cantonetti, Veronica,Monti, Donato,Venanzi, Mariano,Bombelli, Cecilia,Ceccacci, Francesca,Mancini, Giovanna
, p. 1969 - 1977 (2007/10/03)
The inclusion behaviour of porphyrin derivative manganese [5-(4-(carboxyphenyl-(N-L-proline)))-10-15-20-triphenylporphyrinyl] chloride 1MnCl in micellar aggregates of sodium N-dodecanoyl-L-prolinate L-SDP and of sodium dodecylsulfate SDS has been studied by means of several spectroscopic techniques. The catalytic activity in the epoxidation reaction of some test chiral olefins has been also investigated. Comparison with the case of the related manganese[5-(4-carboxyphenyl)-10-15-20-triphenylporphyrinyl] chloride 2MnCl, gave evidence that suggests the presence of a chiral functionality on the periphery of porphyrin macrocycles affects their aggregation mode within the biomembrane models. This results in the modulation of their stereoselective Cytochrome P450 biomimetic activity.
A cyclodextrin-modified ketoester for stereoselective epoxidation of alkenes
Chan, Wing-Kei,Yu, Wing-Yiu,Che, Chi-Ming,Wong, Man-Kin
, p. 6576 - 6582 (2007/10/03)
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).