1439-07-2Relevant academic research and scientific papers
Epoxidation and hydroxylation reactions catalyzed by the manganese and iron complexes of 5,10,15,20-tetrakis(2,6-dimethoxyphenyl)porphyrin
Baciocchi, Enrico,Boschi, Tristano,Galli, Carlo,Lapi, Andrea,Tagliatesta, Pietro
, p. 4497 - 4502 (1997)
Manganese(III) and iron(III) complexes of 5,10,15,20-tetrakis-(2,6-dimethoxyphenyl)porphyrin (H2TDMeOPP) were tested as catalysts in the epoxidation of alkenes and in the hydroxylation of adamantane with H2O2 (in the prese
Highly active Ga promoted Co-HMS-X catalyst towards styrene epoxidation reaction using molecular O2
Rahman, Sumbul,Santra, Chiranjit,Kumar, Rawesh,Bahadur, Jitendra,Sultana, Asima,Schweins, Ralf,Sen, Debasis,Maity, Sudip,Mazumdar,Chowdhury, Biswajit
, p. 61 - 68 (2014)
Atom efficient synthesis of various value added products has been focused as an intense research area after Kyoto protocol. Styrene epoxidation is a challenging reaction as styrene epoxide is an important monomer for large number of polymers. It has been found that surface acidity and redox property of the catalyst has a major contribution to the catalytic activity for oxidation reaction. In this study Co-HMS-X catalyst was prepared and characterized by BET surface area and porosity measurement, SAXS, SANS, FESEM, HRTEM, UV-vis spectra, FTIR, 29Si NMR, H2-TPR and NH3-TPD techniques. It is observed that 5 mol% Co-HMS-X showed highest catalytic activity for styrene epoxidation reaction using molecular O2 as an oxidant. Interestingly it is found that among three different dopant (Al, Ga, Tl), the Ga promoted Co-HMS-X catalyst (Si:Co:Ga = 100:5:1.25) showed highest catalytic activity in terms of styrene conversion (100%) and styrene epoxide selectivity (68%). The unusual trend of Al, Ga and Tl towards the activity of Co-HMS-X (5 mol%) catalyst has been discussed from the results obtained in the H 2-TPR and NH3-TPD study.
Cp* iridium complexes give catalytic alkane hydroxylation with retention of stereochemistry
Zhou, Meng,Schley, Nathan D.,Crabtree, Robert H.
, p. 12550 - 12551 (2010)
A series of Cp Ir complexes can catalyze C-H oxidation, with ceric ammonium nitrate as the terminal oxidant and water as the source of oxygen. Remarkably the hydroxylation of cis-decalin and 1,4-dimethylcyclohexane proceeds with retention of stereochemistry. With H2O18, cis-decalin oxidation gave 18O incorporation into the product cis-decalol.
Catalytic activity of Mn(III) and Fe(III) complexes of meso-tetra(n-propyl) porphyrin in oxidation of olefins: Meso-alkyl substituent in comparison with the alkenyl and aryl ones
Zakavi, Saeed,Talebzadeh, Sadegh,Rayati, Saeed
, p. 368 - 372 (2012)
Catalytic activity of Mn(III) and Fe(III) complexes of meso-tetra(n-propyl) porphyrin, MnT(n-Pr)P(X) and FeT(n-Pr)P(X) (X = Cl, SCN, OAc) in oxidation of olefins with tetra-n-butylammonium periodate at room temperature has been studied. The influence of different parameters including the molar ratio of catalyst to imidazole, type of counter ion (X) and oxidative stability of metalloporphyrins on the efficiency of the catalysts was investigated. The results of competitive oxidation of cis- and trans-stilbene suggest the presence of a high-valent Mn-oxo as the predominant oxidant species in equilibrium with a six coordinate complex, MnT(n-Pr)P(ImH)(IO4) in the case of MnT(n-Pr)P(OAc). An unusual preference for trans-stilbene over cis-stilbene was observed in the reaction catalyzed by FeT(n-Pr)P(OAc). Control reaction indicated a significant cis- to trans-isomerization (81%) in oxidation of cis-stilbene catalyzed by FeT(n-Pr)P(OAc) which may explain the observed unusual cis to trans-stilbene oxide ratio. While oxidation of cyclooctene and styrene led to the exclusive formation of the corresponding epoxides, oxidation of cyclohexene gave 2-cyclohexe-1-ol and cyclohexene oxide as the products. However, the results of this study clearly demonstrate the key role played by the group substituted at the meso positions of metalloporphyrins on their catalytic activity, apart from the electron-donating or electron-withdrawing properties of the substituents.
Metal-cation-directed de novo assembly of a functionalized guest molecule in the nanospace of a metal-organic framework
Li, Baiyan,Zhang, Yiming,Ma, Dingxuan,Ma, Tianliang,Shi, Zhan,Ma, Shengqian
, p. 1202 - 1205 (2014)
In this work, a new strategy is developed to encapsulate a metal-functionalized guest molecule into a metal-organic framework (MOF) via metal-cation-directed de novo assembly from the component fragments of the guest molecule. This strategy, as illustrate
Comparative study of catalytic activity of some biomimetic models of cytochrome P450 in oxidation of olefins with tetra-n-butylammonium periodate: Electron-rich Mn-porphyrins versus the electron-deficient ones
Zakavi, Saeed,Heidarizadi, Fatemeh,Rayati, Saeed
, p. 1010 - 1013 (2011)
Oxidation of a wide range of cyclic and acyclic olefins with tetra-n-butylammonium periodate shows different orders of catalytic activity for a series of electron-rich and electron-deficient Mn-porphyrins in oxidation of various alkenes. While the Mn(III) complex of meso-tetra(4-thiomethoxyphenyl) porphyrin, MnT(4-SCH3P)P(OAc), has the highest activity among the series, the β tetra-brominted derivative shows the lowest catalytic efficiency for the oxidation of the used olefins with the exception of cis- and trans-stilbene. The results clearly show that the electron-withdrawing effects of meso- and β-substituents may increase or decrease the catalytic activity of Mn-porphyrins in the case of different olefins.
Oxygen atom transfer from a chiral oxaziridinium salt. Asymmetric epoxidation of unfunctionalized olefins
Bohe, Luis,Lusinchi, Marie,Lusinchi, Xavier
, p. 141 - 154 (1999)
The synthesis of an optically pure oxaziridinium salt from (1S,2R)-(+)- norephedrine and the study of the asymmetric oxygen transfer reactions from this reagent to unfunctionalized olefins are described.
Use of titanium-containing silica catalysts prepared by rapid and straightforward method in selective oxidations
Pirovano,Guidotti,Dal Santo,Psaro,Kholdeeva,Ivanchikova
, p. 170 - 177 (2012)
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.
NiO promoted CuO-NiO/SBA-15 composites as highly active catalysts for epoxidation of olefins
Tang, Yinhai,Gao, Hongyi,Yang, Mu,Wang, Ge,Li, Jie,Zhang, Huan,Tao, Zhang
, p. 8543 - 8548 (2016)
In this paper, CuO-NiO supported on mesoporous silica SBA-15 was developed using the ultrasonic post-grafting method. The bi-metallic oxides were well-dispersed in very small sizes in the mesoporous channels, and the presence of NiO enhanced the surface content of CuO, leading to a redistribution of CuO and good dispersion of CuO nanoparticles, which were characterized by high-resolution transmission electron microscopy (HRTEM), XRD and N2 adsorption and desorption isotherm examination. Compared with the CuO/SBA-15 or NiO/SBA-15, the electron transfer that occurred between the two metal oxides and high dispersion of the active components improved the overall selective olefin oxidation.
Catalytic ferrocenyl sulfides for the asymmetric transformation of aldehydes into epoxides
Miniere, Stephanie,Reboul, Vincent,Metzner, Patrick,Fochi, Mariafrancesca,Bonini, Bianca Flavia
, p. 3275 - 3280 (2004)
Six ferrocenyl sulfides, exhibiting planar and central chiralities, have been screened as a catalytic source of asymmetric sulfonium ylides. A one-pot reaction has been achieved, involving the addition of an aldehyde, benzyl bromide, 20% molar equivalent of the ferrocenyl sulfide, sodium iodide in a mixture of tert-butanol and water. The best results were observed with enantiopure sulfide 3a, bearing a tert-butyl group. Good yields of stilbene oxides were obtained, with enantiomeric excesses ranging from 74% to 94%. trans/cis-Diastereomeric ratios ranged from 60:40 to 86:14. The chiral sulfide was recovered. An unexpected case of stereoconvergence was observed with diastereoisomers 3a and 3b. A model is proposed to account for the asymmetric induction, based on a conformation locked by the tert-butyl group and the interplay of planar and remote central chiralities.
