96-09-3Relevant articles and documents
Aminopropyl group-modified SBA-15 covalent attachment Mn(salen) complexes as catalysts for styrene epoxidation
Liu, Lili,Hu, Jianglei,He, Jiaojiao,Lu, Haojie,Xu, Yong,Shi, Fengwei
, p. 76 - 81 (2016)
A series of aminopropyl group-modified ordered mesoporous silica materials impregnated with Mn(salen) were prepared using successive grafting procedures. The prepared composite catalysts were well characterized by inductively coupled plasma atomic emissio
Are MnIV species involved in Mn(salen)-satalyzed Jacobsen-Katsuki epoxidations? A mechanistic elucidation of their formation and reaction modes by EPR spectroscopy, mass-spectral analysis, and product studies: Chlorination versus oxygen transfer
Adam, Waldemar,Mock-Knoblauch, Cordula,Saha-Moeller, Chantu R.,Herderich
, p. 9685 - 9691 (2000)
EPR and ESI-MS/MS evidence is presented that in the absence of an olefinic substrate the reaction between the MnIII(salen) complexes A1 (X = Cl) and A2 (X = PF6) and PhIO or NaOCl as oxygen sources leads to paramagnetic MnIV(salen) complexes. Depending on the solvent and the counterion, two distinct MnIV-(salen) complexes intervene. In CH2Cl2, regardless of the counterion, a ClOMnIV(salen) complex (B1) and a HOMnIV(salen) complex (B1′) are formed by Cl and H atom abstraction from CH2Cl2, and the latter deprotonates to the neutral OMnIV(salen) complex (B2). In EtOAc as solvent, only the complex B2 is obtained from A1 (X = Cl), presumably by inner-sphere electron transfer from the chloride ion. The MnIV(salen) complexes display the following reaction modes toward 1,2-dihydronaphthalene (1), styrene (2), and the radical probe 3 as substrates: Complex B1 chlorinates the olefins 1/2 through an electrophilic pathway to yield the 1,2-dichloro adducts 1a/2a and the chlorohydrins 1b/2b (nucleophilic trapping of the initially formed benzylic cation), while with olefin 3 the ring-opened dichloro product 3a results. Complex B2, however, epoxidizes these olefins through a radical pathway, as evidenced by the formation of isomerized stilbene oxide 4c (cis/trans ratio 36: 64) from cis-stilbene (4). The relevance of these paramagnetic MnIV(salen) species in Jacobsen-Katsuki catalytic epoxidations is scrutinized.
Gold nanoparticles supported on cellulose aerogel as a new efficient catalyst for epoxidation of styrene
Keshipour, Sajjad,Khezerloo, Masoumeh
, p. 1107 - 1112 (2017)
A new efficient heterogeneous catalyst was introduced for the epoxidation of styrene. The catalyst was obtained from deposition of gold nanoparticles on the cellulose aerogel. The catalyst was characterized with XRD, TGA, EDX, BET, FAAS and SEM. High yield and excellent selectivity were achieved for the epoxidation of styrene in solvent-free conditions at room temperature using H2O2 as a green oxidant during 1?h. The reaction has some advantages such as solvent-free and mild reaction conditions, low catalyst loading, high yield, excellent selectivity, green oxidant and short reaction duration. In addition, the catalyst is recyclable and applicable for six times without decrease in yield.
Colloidal gold immobilized on mesoporous silica as a highly active and selective catalyst for styrene epoxidation with H2O2
Linares,Canlas,Garcia-Martinez,Pinnavaia
, p. 50 - 53 (2014)
Colloidal gold nanoparticles were synthesized by different procedures affording suspensions with two different mean sizes (2 and 5 nm). Au catalysts were prepared by sol immobilization onto several silica frameworks with different 2D and 3D mesoporosities. The catalysts were tested in styrene oxidation reactions showing excellent efficiency and selectivity. The effect of nanoparticle size and mesoporous framework on the physical and catalytic properties of the final materials was studied. The most selective catalyst was prepared from the 5 nm Au nanoparticles and the more interconnected silica framework (3D mesoporosity).
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.
Self-assembly of reverse micelle nanoreactors by zwitterionic polyoxometalate-based surfactants for high selective production of β?hydroxyl peroxides
An, Sai,Chang, Wen,Hu, Guicong,Qi, Bo,Song, Yu-Fei
supporting information, (2022/03/08)
Surfactants with polyoxometalates (POMs) as polar head groups have shown fascinating self-assembly behaviors and various functional applications. However, self-assembly them into reverse micelles is still challenging owing to the large molecular size and intermolecular strong electrostatic repulsions of POM heads. In this work, a zwitterionic POM-based surfactant was synthesized by covalently grafting two cationic long alkyl tails onto the lacunary site of [PW11O39]7?. With decreased electrostatic repulsions and increased hydrophobic effect, the POM-based reverse micelles with an average diameter of 5 nm were obtained. Interestingly, when these reverse micelles were applied for catalyzing the oxidation of styrene, an unprecedented β?hydroxyl peroxide compound of 2?hydroxyl-2-phenylethan-1?tert-butylperoxide was produced in high selectivity of 95.2%. In comparison, the cetyltrimethylammonium electrostatically encapsulated POMs mainly generated the epoxides or 1,2-diols. A free radical mechanism was proposed for the oxidation reaction catalyzed by the zwitterionic POM surfactants.
