96-08-2Relevant academic research and scientific papers
Oxygen Atom Transfer Mechanism for Vanadium-Oxo Porphyrin Complexes Mediated Aerobic Olefin Epoxidation
Han, Qi,Huang, Jia-Ying,Ji, Hong-Bing,Liu, Xiao-Hui,Tao, Lei-Ming,Xue, Can,Yu, Hai-Yang,Zhou, Xian-Tai,Zou, Wen
supporting information, p. 115 - 122 (2021/12/04)
The development of catalytic aerobic epoxidation by numerous metal complexes in the presence of aldehyde as a sacrificial reductant (Mukaiyama epoxidation) has been reported, however, comprehensive examination of oxygen atom transfer mechanism involving free radical and highly reactive intermediates has yet to be presented. Herein, meso-tetrakis(pentafluorophenyl) porphyrinatooxidovanadium(IV) (VOTPFPP) was prepared and proved to be efficient toward aerobic olefin epoxidation in the presence of isobutyraldehyde. In situ electron paramagnetic resonance spectroscopy (in situ EPR) showed the generation, transfer pathways and ascription of free radicals in the epoxidation. According to the spectral and computational studies, the side-on vanadium-peroxo complexes are considered as the active intermediate species in the reaction process. In the cyclohexene epoxidation catalyzed by VOTPFPP, the kinetic isotope effect value of 1.0 was obtained, indicating that epoxidation occurred via oxygen atom transfer mechanism. The mechanism was further elucidated using isotopically labeled dioxygen experiments and density functional theory (DFT) calculations.
Liquid-phase oxidation of olefins with rare hydronium ion salt of dinuclear dioxido-vanadium(V) complexes and comparative catalytic studies with analogous copper complexes
Maurya, Abhishek,Haldar, Chanchal
, (2021/02/26)
Homogeneous liquid-phase oxidation of a number of aromatic and aliphatic olefins was examined using dinuclear anionic vanadium dioxido complexes [(VO2)2(salLH)]? (1) and [(VO2)2(NsalLH)]? (2) and dinuclear copper complexes [(CuCl)2(salLH)]? (3) and [(CuCl)2(NsalLH)]? (4) (reaction of carbohydrazide with salicylaldehyde and 4-diethylamino salicylaldehyde afforded Schiff-base ligands [salLH4] and [NsalLH4], respectively). Anionic vanadium and copper complexes 1, 2, 3, and 4 were isolated in the form of their hydronium ion salt, which is rare. The molecular structure of the hydronium ion salt of anionic dinuclear vanadium dioxido complex [(VO2)2(salLH)]? (1) was established through single-crystal X-ray analysis. The chemical and structural properties were studied using Fourier transform infrared (FT-IR), ultraviolet–visible (UV–Vis), 1H and 13C nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry (ESI-MS), electron paramagnetic resonance (EPR) spectroscopy, and thermogravimetric analysis (TGA). In the presence of hydrogen peroxide, both dinuclear vanadium dioxido complexes were applied for the oxidation of a series of aromatic and aliphatic alkenes. High catalytic activity and efficiency were achieved using catalysts 1 and 2 in the oxidation of olefins. Alkenes with electron-donating groups make the oxidation processes easy. Thus, in general, aromatic olefins show better substrate conversion in comparison to the aliphatic olefins. Under optimized reaction conditions, both copper catalysts 3 and 4 fail to compete with the activity shown by their vanadium counterparts. Irrespective of olefins, metal (vanadium or copper) complexes of the ligand [salLH4] (I) show better substrate conversion(%) compared with the metal complexes of the ligand [NsalLH4] (II).
Kinetic investigation of aerobic epoxidation of limonene over cobalt substituted mesoporous SBA-16
Madadi, Sara,Bergeron, Jean-Yves,Kaliaguine, Serge
, p. 594 - 611 (2021/02/09)
Incorporation of low coordination Co2+within the structure of mesoporous silica SBA-16 has been accomplished through a facile and green “pH adjusting” method. The resulting materials were used as heterogeneous catalysts for aerobic Mukaiyama epoxidation of limonene in the presence of isobutyraldehyde, under very mild conditions. The structural integrity during the pH adjustment procedure at various loadings and states of cobalt ions within the mesoporous structure were determined using characterization techniques including nitrogen physisorption, X-ray fluorescence, diffuse reflectance UV-vis, scanning electron microscopy, temperature-programmed reduction, X-ray photoelectron spectroscopy and powder X-ray diffraction. These catalysts showed quite high reactivity for the epoxidation of limonene with high epoxide yields under optimized oxygen pressure. In this work, a thorough kinetic analysis of aerobic epoxidation of limonene was investigated to allow proposing a reaction scheme. A new mechanism, in which a surface reaction between a Co3+OO?peroxo intermediate and limonene was found to be involved in the formation of the epoxidized limonene. The kinetics developed from the proposed mechanism was accurately fitted with extensive experimental initial reaction rate data. The activation energy for limonene mono epoxide formation was determined to be 22 kJ mol?1
A new and efficient methodology for olefin epoxidation catalyzed by supported cobalt nanoparticles
Rossi-Fernández, Lucía,Dorn, Viviana,Radivoy, Gabriel
supporting information, p. 519 - 526 (2021/03/31)
A new heterogeneous catalytic system consisting of cobalt nanoparticles (CoNPs) supported on MgO and tert-butyl hydroperoxide (TBHP) as oxidant is presented. This CoNPs@MgO/t-BuOOH catalytic combination allowed the epoxidation of a variety of olefins with good to excellent yield and high selectivity. The catalyst preparation is simple and straightforward from commercially available starting materials and it could be recovered and reused maintaining its unaltered high activity.
New heptacoordinate tungsten(II) complexes with α-diimine ligands in the catalytic oxidation of multifunctional olefins
Vasconcellos-Dias, Maria,Nunes, Carla D.,Félix, Vítor,Brand?o, Paula,Calhorda, Maria José
, (2021/02/26)
New tungsten(II) and molybdenum(II) heptacoordinate complexes [MX2(CO)3(LY)] (MXLy: M = W, Mo; X = Br, I; LY = C5H4NCY = N(CH2)2CH3 with Y = H (L1), Me (L2), Ph (L3)) were synthesized and characterized by spectroscopic techniques and elemental analysis. The two tungsten complexes WXL1 (X = Br, I) were also structurally characterized by single crystal X-ray diffraction. The metal coordination environment is in both a distorted capped octahedron. The complexes with L1 and L2 ligands were grafted in MCM-41, after functionalization of the ligands with a Si(OEt)3 group. The new materials were characterized by elemental analysis, N2 adsorption isotherms, 29Si MAS and 13C MAS NMR. The tungsten(II) complexes and materials were the first examples of this type reported. All complexes and materials were tested as homogeneous and heterogeneous catalysts in the oxidation of multifunctional olefins (cis-hex-3-en-1-ol, trans-hex-3-en-1-ol, geraniol, S-limonene, and 1-octene), with tert-butyl hydroperoxide (TBHP) as oxidant. The molybdenum(II) catalyst precursors are in general very active, reaching 99% conversion and 100% selectivity in the epoxidation of trans-hex-3-en-1-ol. Their performance is comparable with that of the [Mo(η3-C3H5)X(CO)2(LY)] complexes, but it increases with immobilization. On the other hand, most of the W(II) complexes display an activity similar or inferior to that of the Mo(II) analogues and it decreases after they are supported in MCM-41. DFT calculations show that tungsten complexes and iodide ligands are more easily oxidized from M(II) to M(VI) than molybdenum ones, while the energies of relevant species in the catalytic cycle are very similar for all complexes, making the theoretical rationalization of experimental catalytic data difficult.
Anchoring of a terpyridine-based Mo(VI) complex on manganese ferrite as a recoverable catalyst for epoxidation of olefins under solvent-free conditions
Fadaei Sarabi, Mahsa,Bezaatpour, Abolfazl,Mahmoudi, Ali
, p. 1597 - 1612 (2021/03/29)
A magnetically separable heterogeneous nanocatalyst was obtained by anchoring a terpyridine-based Mo(VI) complex on modified MnFe2O4 nanoparticles and characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and diffuse reflectance spectroscopies (DRS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analysis. The catalytic activity of the supported molybdenum based catalyst was evaluated in the selective epoxidation of various olefins (cyclooctene, limonene, 1-dodecane, 1-heptene, styrene, 1-indene, α-pinene, cyclohexene) with tert-butyl hydroperoxide (TBHP) as an oxidant under solvent-free conditions. This nanocatalyst was easily separated by using an external magnetic field and reused consecutively at least five times with no significant loss in selectivity and catalytic activity. The short reaction time, simple preparation, high conversion, good physicochemical stability and magnetic recycling of the catalysts are beneficial.
Heterogeneous catalysis with an organic-inorganic hybrid based on MoO3chains decorated with 2,2′-biimidazole ligands
Amarante, Tatiana R.,Neves, Patrícia,Almeida Paz, Filipe A.,Gomes, Ana C.,Pillinger, Martyn,Valente, Anabela A.,Gon?alves, Isabel S.
, p. 2214 - 2228 (2021/04/12)
The discovery of selective heterogeneous catalytic systems for industrial oxidation processes remains a challenge. Molybdenum oxide-based polymeric hybrid materials have been shown to be oxidation catalysts under mild reaction conditions, although difficulties remain with catalyst recovery/reuse since most perform as homogeneous catalysts or possess low activity. The present study shows that the hybrid material [MoO3(2,2′-biimidazole)]·H2O (1) is a superior catalyst regarding these issues. The structure of1was confirmed (by single crystal and synchrotron X-ray powder diffraction) to comprise one-dimensional chains of corner-sharing {MoO4N2} octahedra. Strong MoO?H-N hydrogen bonds separate adjacent chains to afford parallel channels that are occupied by disordered water molecules. Hybrid1was additionally characterised by FT-IR spectroscopy,1H and13C MAS NMR, scanning electron microscopy and thermogravimetric analysis. The catalytic studies highlighted the versatility of1for oxidation reactions withtert-butylhydroperoxide as oxidant. By complementing with characterisation studies, it was verified that the reaction occurs in the heterogeneous phase, the catalyst has good stability and is recoverableviasimple procedures. The chemical reaction scope covered epoxidation and sulfoxidation, and the substrate scope included biomass-deriveddl-limonene and fatty acid methyl esters to give renewable bio-products, as well as thiophene and thioanisole substrates.
Aldehyde-catalyzed epoxidation of unactivated alkenes with aqueous hydrogen peroxide
Kokotos, Christoforos G.,Kokotou, Maroula G.,Lotter, Dominik,Sparr, Christof,Triandafillidi, Ierasia
, p. 10191 - 10196 (2021/08/12)
The organocatalytic epoxidation of unactivated alkenes using aqueous hydrogen peroxide provides various indispensable products and intermediates in a sustainable manner. While formyl functionalities typically undergo irreversible oxidations when activating an oxidant, an atropisomeric two-axis aldehyde capable of catalytic turnover was identified for high-yielding epoxidations of cyclic and acyclic alkenes. The relative configuration of the stereogenic axes of the catalyst and the resulting proximity of the aldehyde and backbone residues resulted in high catalytic efficiencies. Mechanistic studies support a non-radical alkene oxidation by an aldehyde-derived dioxirane intermediate generated from hydrogen peroxide through the Payne and Criegee intermediates.
Limonene dioxide as a building block for 100% bio-based thermosets
Mija, Alice,Louisy, Elodie,Lachegur, Sara,Khodyrieva, Veronika,Martinaux, Philippe,Olivero, Sandra,Michelet, Veronique
supporting information, p. 9855 - 9859 (2021/12/24)
This study valorises the benign epoxidation of (R)-(+)-limonene to generate novel bio-resourced limonene dioxide monomers. Without additional steps of separation or functionalization, the racemic limonene dioxide was cured with glutaric and dimethylglutaric anhydrides leading to thermosets with a high Tg (～98 °C) and good mechanical properties (σ = 27 MPa; ? = 3.5%; E = 1150 MPa; E′ = 1650 MPa, Shore D = 78). This journal is
Sustainable catalytic epoxidation of biorenewable terpene feedstocks using H2O2as an oxidant in flow microreactors
Bull, Steven D.,Cunningham, William B.,Plucinski, Pawel,Tibbetts, Joshua D.,Vezzoli, Massimiliano
supporting information, p. 5449 - 5455 (2021/08/16)
Solvent-free continuous flow epoxidation of the alkene bonds of a range of biorenewable terpene substrates have been carried out using a recyclable tungsten-based polyoxometalate phase transfer catalyst and aqueous H2O2 as a benign oxidant. These sustainable flow epoxidation reactions are carried out in commercial microreactors containing static mixing channels that enable common monoterpenes (e.g. untreated crude sulfate turpentine, limonene, etc.) to be safely epoxidized in short reaction times and in good yields. These flow procedures are applicable for the flow epoxidation of trisubstituted and disubstituted alkenes for the safe production of multigram quantities of a wide range of epoxides. This journal is
