23202-10-0Relevant articles and documents
Selectively oxidized carbon nanocatalysts for the oxidation of: Cis -cyclooctene
Jarrais, Bruno,Guedes, Alexandra,Freire, Cristina
, p. 2306 - 2319 (2018)
In this work, selectively oxidized carbon nanotubes and graphene flakes were used as carbocatalysts in the mild oxidation of cis-cyclooctene. Firstly, the multi-walled carbon nanotubes and graphene flakes were oxidized using three different oxidation procedures: (i) nitric acid treatment; (ii) nitric acid followed by thermal treatment at 400 °C; (iii) gas phase oxidation with O2, and subsequently characterized by several techniques. Both oxidized nanomaterials showed an overall increase in the oxygen content and revealed that the different oxidation procedures promoted different superficial chemical compositions: nitric acid treated carbon nanotubes and graphene flakes (respectively, MWCNTh and GFh) presented increased amounts of carboxylic acids, anhydrides and phenols up to 552, 84, and 648 μmol g-1, respectively, for material MWCNTh, and 612, 120, and 1392 μmol g-1, respectively, for material GFh; the nanomaterials treated with nitric acid followed by thermal treatment at 400 °C (MWCNTht and GFht) presented a loss of carboxylic acids and an increase in carboxylic anhydride content (36 and 132 μmol g-1, respectively, for material MWCNTht, and 36 and 156 μmol g-1, respectively, for material MWCNTht), when compared to the nitric acid treated materials MWCNTh and GFh; and finally the gas phase treated nanomaterials, MWCNTo and GFo, presented an increase in the amounts of phenols, carbonyls/quinones, and lactones up to 720, 216, and 144 μmol g-1, respectively, for material MWCNTo, and 804, 420, and 144 μmol g-1, respectively, for material GFo. The carbon nanocatalysts showed activity in the selective oxidation of cis-cyclooctene to epoxycyclooctane using mild conditions: hydrogen peroxide was used as oxidant at 80 °C. The modifications introduced in the pristine materials through nitric acid followed by thermal treatment at 400 °C originated the nanocatalysts with the best activity and selectivity: MWCNTht presented 47% of substrate conversion and 79% epoxycyclooctane selectivity whereas GFht showed 57% conversion and 85% epoxycyclooctane selectivity. Reusability experiments revealed no loss of catalytic activity up to three catalytic cycles. The results indicate that the fine tuning of the carbon nanomaterials through appropriate oxidation procedures is crucial in achieving metal-free carbocatalysts with enhanced performance and selectivity in selective oxidation reactions.
Two kinds of cobalt–based coordination polymers with excellent catalytic ability for the selective oxidation of cis-cyclooctene
Zhang, Guangju,Shi, Yang,Wei, Ying,Zhang, Qingguo,Cai, Kedi
, p. 112 - 117 (2017)
Two kinds of cobalt–based coordination polymers {[Co(dsd)(H2O)4]·4,4′-bpy}(1) and {[Co(dsd)(H2O)4]·H2O} (2) with the chain structure possess excellent catalytic ability for the selective oxidation of
Polymer-anchored mononuclear and binuclear CuII Schiff-base complexes: Impact of heterogenization on liquid phase catalytic oxidation of a series of alkenes
Maurya, Abhishek,Kesharwani, Neha,Kachhap, Payal,Mishra, Vivek Kumar,Chaudhary, Nikita,Haldar, Chanchal
, (2019/08/12)
Liquid phase catalytic oxidation of a number of alkenes, for example, cyclohexene, cis-cyclooctene, styrene, 1-methyl cyclohexene and 1-hexene, was performed using polymer-anchored copper (II) complexes PS-[Cu (sal-sch)Cl] (5), PS-[Cu (sal-tch)Cl] (6), PS-[CH2{Cu (sal-sch)Cl}2] (7) and PS-[CH2{Cu (sal-tch)Cl}2] (8). Neat complexes [Cu (sal-sch)Cl] (1), [Cu (sal-tch)Cl] (2), [CH2{Cu (sal-sch)Cl}2] (3) and [CH2{Cu (sal-tch)Cl}2] (4) were isolated by reacting CuCl2·2H2O with [Hsal-sch] (I), [Hsal-tch] (II), [H2bissal-sch] (III) and [H2bissal-tch] (IV), respectively, in refluxing methanol. Complexes 1–4 have been covalently anchored in Merrifield resin through the amine nitrogen of the semicarbazide or thiosemicarbazide moiety. A number of analytical, spectroscopic and thermal techniques, such as CHNS analysis, Fourier transform-infrared, UV–Vis, PMR, 13C-NMR, electron paramagnetic resonance, scanning electron microscopy, energy-dispersive X-ray analysis, thermogravimetric analysis, atomic force microscopy, atomic absorption spectroscopy, and electrospray ionization-mass spectrometry, were used to analyze and establish the molecular structure of the ligands (I)–(IV) and complexes (1)–(8) in solid state as well as in solution state. Grafted complexes 5–8 were employed as active catalysts for the oxidation of a series of alkenes in the presence of hydrogen peroxide. Copper hydroperoxo species ([CuIII (sal-sch)-O-O-H]), which is believed to be the active intermediate, generated during the catalytic oxidation of alkenes, are identified. It was found that supported catalysts are very economical, green and efficient in contrast to their neat complexes as well as most of the recently reported heterogeneous catalysts.
Aerobic oxidation of the C-H bond under ambient conditions using highly dispersed Co over highly porous N-doped carbon
Nie, Renfeng,Chen, Jingwen,Chen, Minda,Qi, Zhiyuan,Goh, Tian-Wei,Ma, Tao,Zhou, Lin,Pei, Yuchen,Huang, Wenyu
, p. 1461 - 1466 (2019/03/26)
Highly dispersed Co sites in highly porous N-doped carbon (Co-NC) were synthesized by high-temperature pyrolysis of Zn/Co bimetallic zeolitic imidazolate framework-8 (CoxZn100-x-ZIF). Wide characterization indicated that the pyrolysis atmosphere and temperature play crucial roles in the metal dispersion and pore structure of the resulting materials. A hydrogen treatment at elevated temperatures is found to favour the Zn volatilization and restrict the pore shrinkage of the ZIF precursor, thus yielding efficient catalysts with highly dispersed Co, a high surface area (1090 m2 g-1) and pore volume (0.89 cm3 g-1). When used as a catalyst for aerobic oxidation of ethylbenzene (EB), Co1Zn99-ZIF-800-H2 contributes to 98.9% EB conversion and 93.1% ketone selectivity under mild conditions (60 °C, 1 atm O2), which is 41.3 times more active in comparison to the ZIF-67-derived Co catalyst. Co-NC is stable and could be reused four times without obvious deactivation. This catalyst displays good chemoselectivity to the corresponding ketones when using a broad scope of hydrocarbon compounds.
"ship in a bottle" Porph@MOMs as highly efficient catalysts for selective controllable oxidation and insights into different mechanisms in heterogeneous and homogeneous environments
Saghian,Dehghanpour,Sharbatdaran
, p. 12872 - 12881 (2018/08/01)
In the present work, three "ship in a bottle" Porph@MOMs are reported as biomimetic oxidation catalysts for different reactions. These frameworks are constructed from trimesic acid and metal ions (M = Fe, Co and Mn) in which tetra(N-methyl-4-pyridyl)porphyrin (MTMPyP) is encapsulated within the cavities. Additionally, the catalytic activities of the corresponding homogeneous compounds, FeTMPyP, CoTMPyP and MnTMPyP, and the frameworks without porphyrins within the cavities were investigated in the foregoing oxidation reactions. The prepared 3D porous structures have the ability to control selectivity toward the desired product. Furthermore, they are capable of acting as effective peroxidase mimics, which successfully catalyze the oxidation of diverse olefins as well as hydrocarbons using TBHP as an oxidant. The heterogeneous catalysts significantly enhance conversion in contrast to their corresponding homogeneous systems. Remarkably, an insight into the catalyst behavior was gained from the proposed mechanism based on the reversal of selectivity. Investigation of the stability and reusability of the catalysts revealed the heterogeneity character of the catalyst with no desorption during the course of oxidation reactions. The high yields, clean reactions, high thermal stability and reusability of the catalysts make them good candidates for heterogeneous catalysts in various oxidation reactions.
Chiral Co(II) metal-organic framework in the heterogeneous catalytic oxidation of alkenes under aerobic and anaerobic conditions
Tuci, Giulia,Giambastiani, Giuliano,Kwon, Stephanie,Stair, Peter C.,Snurr, Randall Q.,Rossin, Andrea
, p. 1032 - 1039 (2014/04/03)
The chiral Co(II) MOF [Co(l-RR)(H2O)·H2O] ∞ [1; l-RR = (R,R)-thiazolidine-2,4-dicarboxylate] has been exploited in the catalytic oxidation of different alkenes (cyclohexene, (Z)-cyclooctene, 1-octene) using either tert-butyl hydroperoxide ( tBuOOH) or molecular oxygen (O2) as oxidants. Different chemoselectivities are observed, both substrate- and oxidant-dependent. A moderate enantioselectivity is also obtained in the case of prochiral precursors, revealing the chiral induction ability of the optically pure metal environment. The interaction of O2 with the exposed metal sites in 1 (after material preactivation and consequent removal of the coordinated aquo ligand) has been studied through TPD-MS analysis combined with DFT calculations, with the aim of probing effective oxygen uptake by the heterogeneous catalyst and unraveling the nature of the active species in the catalytic oxidation process under aerobic conditions. Theoretical results indicate the presence of an η1-superoxo species at the cobalt center, with concomitant Co(II) ? Co(III) oxidation. Finally, the experimental estimation of the O2 adsorption enthalpy is found to be in good agreement with the calculated binding energy.
Effective oxidation of benzylic and alkane C-H bonds catalyzed by sodium o-iodobenzenesulfonate with Oxone as a terminal oxidant under phase-transfer conditions
Cui, Li-Qian,Liu, Kai,Zhang, Chi
experimental part, p. 2258 - 2265 (2011/05/08)
Catalytic oxidation of benzylic C-H bonds could be efficiently realized using IBS as a catalyst which was generated in situ from the oxidation of sodium 2-iodobenzenesulfonate (1b) by Oxone in the presence of a phase-transfer catalyst, tetra-n-butylammonium hydrogen sulfate, in anhydrous acetonitrile at 60 °C. Various alkylbenzenes, including toluenes and ethylbenzenes, several oxygen-containing functionalities substituted alkylbenzenes, and a cyclic benzyl ether could be efficiently oxidized. And, the same reagent system of cat. 1b/Oxone/cat. n-Bu4NHSO4 could be applied to the effective oxidation of alkanes as well.
Novel transition-metal-free heterogeneous epoxidation catalysts discovered by means of high-throughput experimentation
Pescarmona, Paolo P.,Janssen, Kris P. F.,Jacobs, Pierre A.
, p. 6562 - 6572 (2008/03/15)
Various transition-metal-free oxides have been studied as catalysts for the epoxidation of cyclooctene with hydrogen peroxide by means of high-throughput experimentation. Different boron, aluminium, and gallium oxides were prepared according to various synthesis methods. A number of pure aluminium and gallium oxides showed very good catalytic performances, while the results obtained with boron oxides or mixed oxides were less positive. The best results were obtained with a gallium oxide catalyst, which gave an epoxide yield of 71 % and a selectivity of 99% after reaction for 4 h at 80°C. Gallium oxides had not been reported previously as active epoxidation catalysts. The use of high-throughput experimentation proved useful both for discovering new active catalysts and for identifying a number of relationships between the synthesis conditions and the catalytic properties of the transition-metal-free oxides.
Copper-catalyzed rearrangement of vinyl oxiranes
Batory, Lindsay A.,McInnis, Christine E.,Njardarson, Jon T.
, p. 16054 - 16055 (2007/10/03)
A novel copper-catalyzed vinyl oxirane ring expansion protocol has been developed. A wide range of vinyl oxiranes can be rearranged to 2,5-dihydrofurans in excellent yields in the presence of electrophilic copper(II) acetylacetonate catalysts. Regioisomeric vinyl oxiranes can be converted to a single dihydrofuran product using these conditions. This method uses low catalyst loadings (0.5-5 mol %), has good tolerance of substitution patterns, and can be done in the absence of solvent. Copyright
Acetonitrile-assisted highly selective photocatalytic epoxidation of olefins on Ti-containing silica with molecular oxygen
Shiraishi, Yasuhiro,Morishita, Masatsugu,Hirai, Takayuku
, p. 5977 - 5979 (2008/01/27)
Highly selective photocatalytic epoxidation of olefins proceeds on Ti-containing silica with tetrahedrally coordinated Ti-oride species with molecular oxygen and a simple addition of MeCN. The Royal Society of Chemistry 2005.
