- Low-temperature oxidation of isopropylbenzene mediated by the system of NHPI, Fe(acac)3 and 1,10-phenanthroline
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Highly efficient oxidation of isopropylbenzene mediated by the system of NHPI/Fe(acac)3/Phen has been carried out at temperature as low as 60 °C. Significant improvement of catalysis by NHPI was associated with an enhanced oxidizing ability of Fe(III) tandem with Phen, which caused the intense generation of PINO. Furthermore, NMR observations revealed formation of a hydrogen-bonded NHPI-Phen adduct soluble in acetonitrile and isopropylbenzene. Based on this phenomenon, the system was applicable for the oxidation of solvent-free isopropylbenzene. The promise of the system of NHPI/Fe(acac)3/Phen for the selective synthesis of isopropylbenzene hydroperoxide was demonstrated by oxidation at a low content of Fe(acac)3.
- Babushkin, D. E.,Koscheeva, O. S.,Kuznetsova, L. I.,Kuznetsova, N. I.,Zudin, V. N.
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- Zeolite Effect on the Oxidation of Hydrocarbons with Irradiated TiO2 Semiconductor
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The effect of an acidic zeolite on the photocatalytic oxidation of isopropylbenzene and α-methylstyrene over irradiated TiO2 leads to either an increase or a decrease in oxidation rate depending on the substrate but, in both cases, an increase in selectivity is observed.
- Beaune, Olivia,Finiels, Annie,Geneste, Patrick,Graffin, Patrick,Olive, Jean-Louis,Saaedan, Ahmed
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- PHOTOOXIDATION OF SOME AROMATIC SULFONIC ACIDS WITH ALKALINE HYPOCHLORITE.
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Photochemical oxidation of aromatic sulfonic acids such as p-cumenesulfonic, 2-mesitylenesulfonic, 1- and 2-naphthalensulfonic acids with aqueous sodium hypochlorite has been studied. Addition of a large excess of alkali enhances the decomposition of sulfonic acids remarkably. p-Cumenesulfonic and 2-mesitylenesulfonic acids are oxidized faster than 1- and 2-naphthalenesulfonic acids. The photooxidation of sulfonic acids with an equimolar amount of hypochlorite gives intermediary oxidation products involving desulfonation to parent hydrocarbons, aromatic hydroxylation, side-chain oxidation, and ring cleavage; e. g. , p-cumenesulfonic acid gives cumene, 2- and 4-isopropylphenol and 2-phenyl-2-propanol; 1- and 2-naphthalenesulfonic acids give phthalic anhydride. Light-absorbing aromatic sulfonic acids sensitize the decomposition of hypochlorite ion leading to hydroxyl radical, which reacts mainly with ground state sulfonic acid to give radical intermediates.
- Kimura,Ogata
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- Kinetic regularities of conversion of ozone complexes with arenes
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The kinetic regularities of conversion of ozone complexes with several substituted benzenes (ArX = C6H5Me, C6H5Et, C6H5CHMe2, C6H5CMe3, C6H5F, C6H5Cl, m-BrC6H5Me, and C6H5CH2Cl) were studied by spectrophotometry. The rate of consumption of ArX·O3 in a CH2Cl2-ArX solution obeys the kinetic equation W = k0[ArX·O3]+k1[ArX·O 3][ArX]. The values of the rate constants k0 and k1 for the complexes studied were determined at -60÷0°C.
- Avzyanova,Kabal'nova,Shereshovets
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- Aerobic oxidation of cumene catalysed by 4-Alkyloxycarbonyl-N- Hydroxyphthalimide
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4-Hexyloxycarbonyl-, 4-dodecyloxycarbonyl- and 4-hexadecyloxycarbonyl-N- hydroxyphthalimides were synthesised using trimellitic anhydride chloride as the starting material. The obtained lipophilic derivatives of N-hydroxyphthalimide were applied as catalysts of the cumene oxidation reaction with oxygen performed in polar acetonitrile, in non-polar tert-butylbenzene and in the absence of a solvent. The courses of reactions catalysed by N-hydroxyphthalimide and its derivatives were compared. Versita Sp. z o.o.
- Kasperczyk, Kornela,Orlinska, Beata,Zawadiak, Jan
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- Phosphonium ionic liquids as reaction media for strong bases
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Phosphonium ionic liquids are compatible with strong bases; for example, solutions composed of commercially available phenylmagnesium bromide in THF are persistent in tetradecyl(trihexyl)phosphonium chloride for several hours-days: their stability appears to be couched in kinetic terms.
- Ramnial, Taramatee,Ino, Daisuke D.,Clyburne, Jason A. C.
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- Characterization and Reactivity of a Tetrahedral Copper(II) Alkylperoxido Complex
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A tetrahedral CuII alkylperoxido complex [CuII(TMG3tach)(OOCm)]+ (1OOCm) (TMG3tach={2,2′,2′′-[(1s,3s,5s)-cyclohexane-1,3,5-triyl]tris-(1,1,3,3-tetramethyl guanidine)}, OOCm=cumyl peroxide) is prepared and characterized by UV/Vis, cold-spray ionization mass spectroscopy (CSI-MS), resonance Raman, and EPR spectroscopic methods. Product analysis of the self-decomposition reaction of 1OOCm in acetonitrile (MeCN) indicates that the reaction involves O?O bond homolytic cleavage of the peroxide moiety with concomitant C?H bond activation of the solvent molecule. When an external substrate such as 1,4-cyclohexadiene (CHD) is added, the O?O bond homolysis leads to C?H activation of the substrate. Furthermore, the reaction of 1OOCm with 2,6-di-tert-butylphenol derivatives produces the corresponding phenoxyl radical species (ArO.) together with a CuI complex through a concerted proton-electron transfer (CPET) mechanism. Details of the reaction mechanisms are explored by DFT calculations.
- Shimizu, Ikuma,Morimoto, Yuma,Velmurugan, Gunasekaran,Gupta, Tulika,Paria, Sayantan,Ohta, Takehiro,Sugimoto, Hideki,Ogura, Takashi,Comba, Peter,Itoh, Shinobu
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- Solvent-dependent catalytic behavior of telluride-containing guest artificial glutathione peroxidase using cumene hydroperoxide and 3-carboxyl-4-nitrobenzenethiol as substrates
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To reveal the solvent-dependent catalytic behaviour of a hydrophobic telluride-containing guest artificial glutathione peroxidase (ADA-Te-OH), the catalytic rates were investigated using cumene hydroperoxide and 4-nitrobenzenethiol as substrates. Herein, ethanol, DMSO, DMF and CH3CN were selected as the co-solvents in the determination of catalytic rates. Significantly, the typical solvent-dependent catalytic behaviour of ADA-Te-OH was observed. Especially, the higher catalytic rate was observed when polar protic solvent (ethanol) was used compared with other co-solvents. It suggested that polar protic solvent was the appropriate co-solvent for the assay of catalytic activity of hydrophobic artificial glutathione peroxidase. This study well for the understanding of the catalytic behaviour of hydrophobic guest artificial glutathione peroxidase.
- Jiao,Yin,Zhang,Zhong,Wang,Zhang,Yang
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- Kinetic Studies on the Cobalt(II) Naphthenate Catalyzed Decomposition of "Cumene Hydroperoxide" in Benzene
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The cobalt(II) naphthenate catalyzed decomposition of cumene hydroperoxide (CHP) gave a mixture of α-cumyl alcohol, acetophenone and di-α-cumyl peroxide in benzene at 25 deg C.All experimentally observed time courses of disappearing CHP and an increasing of three products compared well with theoretical values.
- Sawada, Hideo,Ishigaki, Hideyo,Kato, Mitsukuni,Nakayama, Masaharu
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- Autooxidation of hydrocarbons with oxygen in ionic liquids as solvents
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The results of hydrocarbons autooxidation process carried out using several ionic liquids (IL) as solvents are demonstrated. Test studies to check the influence of ILs on this process showed that most ILs can accelerate the initiation rate of autooxidation. The results could be very useful for choosing an IL not only for autooxidation processes but also for catalytic oxidation systems.
- Baj, Stefan,Chrobok, Anna
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- A smart artificial glutathione peroxidase with temperature responsive activity constructed by host-guest interaction and self-assembly
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A smart supramolecular artificial glutathione peroxidase (GPx) with tunable catalytic activity was prepared based on host-guest interaction and a blending process. The functional guest molecules ADA-Te with catalytic center, ADA-Arg with binding site and the cyclodextrin-containing host polymers (CD-PNIPAMs) were first synthesized. The artificial glutathione peroxidase was constructed by host-guest interaction of ADA-Te and a series of CD-PNIPAMs with different molecular weights. Through altering the molar ratio of building blocks (CD-PNIPAM73, ADA-Te, ADA-Arg), the optimum artificial GPx (SGPx max) with vesicle structure was prepared via a blending process. Significantly, SGPxmax displayed a noticeable temperature responsive catalytic activity and exhibited typical saturation kinetics behavior of a real enzyme catalyst. It was proved that the change of the self-assembled structure of SGPxmax during the temperature responsive process played a significant role in altering the temperature responsive catalytic behavior. The construction of SGPxmax not only overcomes the insurmountable disadvantages existing in traditional supramolecular artificial GPxs but also bodes well for development of other biologically related functional supramolecular biomaterials.
- Yin, Yanzhen,Jiao, Shufei,Lang, Chao,Liu, Junqiu
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- A new highly active La2O3-CuO-MgO catalyst for the synthesis of cumyl peroxide by catalytic oxidation
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In this study, different magnesium, copper, lanthanide single metal, and composite multimetal oxide catalysts were preparedviathe coprecipitation route for the aerobic oxidation of cumene into cumene hydroperoxide. All catalysts were characterized using several analytical techniques, including XRD, SEM, EDS, FT-IR, BET, CO2-TPD, XPS, and TG-DTG. La2O3-CuO-MgO shows higher oxidation activity and yield than other catalysts. The results of XRD and SEM studies show that the copper and magnesium particles in the catalyst are smaller in size and have a distribution over a larger area due to the introduction of the lanthanum element. The CO2-TPD results confirmed that the catalyst has more alkali density and alkali strength, which can excite active sites and prevent the decomposition of cumene hydroperoxide. XPS results show that due to the promotional effect of La2O3, there are more lattice and active oxygen species in the catalyst, which can effectively utilize the lattice defects under the strong interaction between metal oxides for rapid adsorption and activation, thus improving the oxidation performance. Besides, La2O3-CuO-MgO exhibits good stability and crystalline structure due to its high oxygen mobility inhibiting coking during the cycle stability test. Finally, the possible reaction pathway and promotional mechanism on La2O3-CuO-MgO in cumene oxidation are proposed. We expect this study to shed more light on the nature of the surface-active site(s) of La2O3-CuO-MgO catalyst for cumene oxidation and the development of heterogeneous catalysts with high activity in a wide range of applications.
- Liu, HanShuang,Wang, KaiJun,Cao, XiaoYan,Su, JiaXin,Gu, Zhenggui
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- A kinetic study of the electron-transfer reaction of the phthalimide-N-oxyl radical (PINO) with ferrocenes
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(Chemical Equation Presented) A kinetic study of the one-electron oxidation of a series of ferrocenes (FcX: X = H, CO2Et, CONH2, CH2CN, CH2OH, Et, and Me2) by PINO generated in CH3CN by reaction of N-hydroxyphthalimide (NHPI) with the cumyloxyl radical produced by 355 nm laser flash photolysis of dicumyl peroxide has been carried out. Ferrocenium cations were formed, and the reaction rate was determined by following the decay of PINO radical at 380 nm as a function of the FcX concentration. Rate constants were very sensitive to the oxidation potential of the substrates and exhibited a good fit with the Marcus equation, from which a λ value of 38.3 kcal mol-1 was calculated for the reorganization energy required in the PINO/ferrocenes electron-transfer process. Knowing the ferrocene/ferrocenium self-exchange reorganization energy it was possible to calculate a value of 49.1 kcal mol-1 for the PINO/PINO- self-exchange reaction in CH3CN. Moreover, from the Marcus cross relation and the self-exchange rates of ferrocene and dimethylferrocene, the intrinsic reactivity of PINO in electron-transfer reactions has been calculated as 7.6 × 102 M-1 s-1. The implications of these values and the comparison with the electron-transfer self-exchange reorganization energies of peroxyl radicals are briefly discussed.
- Baciocchi, Enrico,Bietti, Massimo,Di Fusco, Massimo,Lanzalunga, Osvaldo
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- Heterolytic alkyl hydroperoxide O-O bond cleavage by copper(I) complexes
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The reaction of copper(I) complexes and cumene hydroperoxides was examined to demonstrate that heterolytic O-O bond cleavage of the peroxides proceeds predominantly to give the corresponding alcohols (cumyl alcohols) as the major product, when the stoichiometry of CuI/peroxide is 2:1. The result is in sharp contrast to the 1:1 reaction between the copper(II) complexes and cumene hydroperoxide, which provides the ketone (acetophenone) as the major product through homolytic O-O bond cleavage.
- Tano, Tetsuro,Sugimoto, Hideki,Fujieda, Nobutaka,Itoh, Shinobu
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- Mechanism of the Reaction of Cumyloxyl Radicals in a Mixture of Hydrocarbons
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Decay reactions of cumyloxyl radicals have been studied in a mixture of cyclohexane and aromatic hydrocarbon.The hydrogen transfer from solvent to oxyl radical increases considerably when small amounts of the aromatic hydrocarbon are present.The addition of cyclohexyl radical to the aromatic ring plays a decisive role in the mechanism of this reaction.
- Chodak, Ivan,Bakos, Dusan,Mihalov, Vincent
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- Reactivity of copper nanopowders in a model reaction of isopropylbenzene oxidation
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The reactivity of copper nanopowders produced by an electric explosion of a conductor or mechanochemically was studied. Oxidation of isopropylbenzene was used as a model reaction. The dependence of the oxygen uptake rate on the specific surface area of a copper nanopowder and on the method used for its production is discussed. A possible mechanism of isopropylbenzene oxidation in the presence of copper nanopowders is suggested.
- Skorokhodova,Kobotaeva,Sirotkina
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- High-temperature organic reactions at room temperature using plasmon excitation: Decomposition of dicumyl peroxide
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Photoexcitation of gold nanoparticles in their plasmon transition around 530 nm provides the means to carry high-energy reactions at room temperature. In the case of dicumyl peroxide (with activation energy of 34.3 kcal/mol) the reaction occurs in less than 1 min under 532 nm laser excitation. The results suggest that the peroxide is exposed to temperatures of ～500 °C for submicrosecond times, and provides a guide as to which type of organic reactions may benefit from plasmon-mediated energy delivery.
- Fasciani, Chiara,Alejo, Carlos J. Bueno,Grenier, Michel,Netto-Ferreira, Jose Carlos,Scaiano
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- N-Hydroxyphthalimide in combination with Cu(II), Co(II) or Mn(II) salts as catalytic systems for the oxidation of isopropyl-aromatic hydrocarbons with oxygen
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Catalytic systems consisting of N-hydroxyphthalimide in combination with copper(II), cobalt(II) and manganese(II) acetylacetonate, acetate or chloride were applied to the oxidation of cumene with oxygen. The use of these catalytic systems decreases cumyl hydroperoxide selectivity as a result of the decomposition reaction of hydroperoxide to 2-phenyl-2-propanol and acetophenone. It has been demonstrated that the use of N-hydroxyphthalimide in combination with copper salts at 60 °C results in high alcohol content whereas ketone is the major product at 90 °C. The results can be used to develop a method for alcohol or ketone synthesis from other isopropyl-aromatic hydrocarbons.
- Orlińska, Beata
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- Synthesis, characterization, cis-ligand substitution and catalytic alkane hydroxylation by mononuclear nickel(II) complexes stabilized with tetradentate tripodal ligands
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The synthesis and spectroscopic characterization of the mononuclear complexes [Ni(bqenH2)(H2O)2](ClO4)2 1 and [Ni(bqenMe2)(H2O)2](ClO4)2 2 (where bqenH2 = N,N′-bis(8-quinolyl)ethane-1,2-diamine and bqenMe2 = N,N′-dimethyl-N,N′-bis(8-quinolyl)ethane-1,2-diamine) is reported. The bqenMe2 ligand was prepared by a simple modification to the earlier procedure. The reaction of 1 and 2 with 1,10-phenanthroline (phen) or 2,2′-bipyridine (bpy) resulted in the formation of [Ni(bqenH2)(phen)](ClO4)2 3, [Ni(bqenMe2)(phen)](ClO4)2 CH3CN 4, [Ni(bqenH2)(bpy)](ClO4)2 5, and [Ni(bqenMe2)(bpy)](ClO4)2 6. The redox properties of 1-6 are reported. The crystal structures of 3 and 4 consist of distorted octahedral [Ni(bqenH2)(phen)]2+ and [Ni(bqenMe2)(phen)]2+ cations which are stabilized by N-H-O and C-H-O interactions. Compounds 1 and 2 afforded hydroxylation of alkanes with high alcohol to ketone ratio in the presence of m-CPBA oxidant.
- Narulkar, Dattaprasad D.,Patil, Amit R.,Naik, Chandan C.,Dhuri, Sunder N.
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- Copper salt-crown ether systems as catalysts for the oxidation of cumene with 1-methyl-1-phenylethylhydroperoxide to bis(1-methyl-1- phenylethyl)peroxide
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Evidence for phase transfer catalysis in the oxidation of cumene with 1- methyl-1-phenylethylhydroperoxide to bis-(1-methyl-1-phenylethyl)peroxide in the presence of copper salt - crown ether catalysts is given.
- Zawadiak, Jan,Gilner, Danuta,Mazurkiewicz, Roman
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- A copper complex supported by an N2S-tridentate ligand inducing efficient heterolytic O-O bond cleavage of alkylhydroperoxide
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We have recently reported a copper(ii)-superoxide complex supported by an N3-tridentate ligand (LN3), which exhibits a similar structure and reactivity to those of a putative reactive intermediate involved in the catalytic reactions of copper monooxygenases such as peptidylglycine α-hydroxylating monooxygenase (PHM) and dopamine β-monooxygenase (DβM). In this study, we have synthesised and characterised copper complexes supported by a related sulphur-containing ligand (LN2S) to get insight into the notable electronic effect of the sulphur donor atom in the reaction with cumene hydroperoxide, inducing efficient heterolytic O-O bond cleavage.
- Tano, Tetsuro,Mieda, Kaoru,Sugimoto, Hideki,Ogura, Takashi,Itoh, Shinobu
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- Substitution of an amino acid residue axially coordinating to the heme molecule in hexameric tyrosine-coordinated hemoprotein to enhance peroxidase activity
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To convert an originally tyrosine-coordinated heme to histidine-coordinated heme in hexameric tyrosine-coordinated hemoprotein, HTHP, Tyr45, a residue coordinating to the heme cofactor, and Arg25 located in the distal site are replaced with Phe45 and His25, respectively in each of the subunits of the protein. The obtained HTHP mutant (HTHPR25H/Y45F) was characterized by SDS-PAGE, ESI-TOF MS, dynamic light scattering measurements and size exclusion chromatography. These analyses indicate that HTHPR25H/Y45F maintains its stable hexameric structure with the altered ligation of each of the heme cofactors. Comparison of UV-vis absorption spectra of the ferric-, ferrous-, CO-and CN-forms of HTHPR25H/Y45F with those of several well-known His-ligated hemoproteins indicates that heme is coordinated by the His25 residue. The reaction of HTHPR25H/Y45F with cumene hydroperoxide produces both cumyl alcohol and acetophenone in a 2.3:1 ratio, indicating that heterolytic O-O bond cleavage dominantly occurs to form the two-electron oxidized species known as compound I. Peroxidase activity of HTHPR25H/Y45F is found to follow Michaelis-Menten kinetics. The kcat values of HTHPR25H/Y45Ffor H2O2-dependent oxidation of ABTS and guaiacol are 10-and 100-fold higher, respectively, than those of wild type HTHP (HTHPWT). The kcat/Km values of HTHPR25H/Y45F for both substrates are increased 30-fold relative to that of HTHPWT. Moreover, HTHPR25H/Y45F is capable of promoting catalytic sulfoxidation of thioanisole with H2O2 with a turnover number ca. 2-fold higher than that of HTHPWT. The present findings demonstrate that proximal His ligation to the heme is significantly effective to increase the peroxidase activity in the HTHP matrix.
- Mashima, Tsuyoshi,Oohora, Koji,Hayashi, Takashi
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- Direct Comparison of Photoefficiencies of C-C Bond Scission in Radical Cations generated by Photosensitized Electron-Transfer and by Irradiation of Charge-transfer Complexes
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Quantum yields for C-C bond scission are at least 50 times larger in radical cations of methoxybicumenes (1.*) generated by quenching of the p-tetrachlorobenzoquinone (TCBQ) excited state (a process that results in triplet solvent-separeted ion pairs) than in those obtained by the irradiation of charge-transfer complexes (a reaction that yields singlet contact ion pairs).
- Maslak, Przemyslaw,Chapman, Jr. William H.
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- Kinetic solvent effects on hydrogen abstraction reactions
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Kinetic solvent effects on hydrogen abstractions, namely, acceleration in nonpolar solvents, have been presumed to be restricted to O-H hydrogen donors. We demonstrate that also abstractions from C-H and even Sn-H bonds by cumyloxyl radicals and n,πz.ast;-excited 2,3-diazabicyclo[2.2.2]oct-2-ene are fastest in the gas phase and nonpolar solvents but slowest in acetonitrile. Accordingly, solvent effects on hydrogen abstractions are more general, presumably due to stabilization of the reactive oxygen or nitrogen species in polar solvents.
- Koner, Apurba L.,Pischel, Uwe,Nau, Werner M.
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- Role of electron transfer processes in the oxidation of aryl sulfides catalyzed by nonheme iron complexes
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The oxidation of a series of aryl 1-methyl-1-phenylethyl sulfides with H2O2catalyzed by the two tetradentate nonheme-iron complexes [(PDP)FeII(SbF6)2] and [(BPMCN)FeII(OTf)2] occurs by an electron transfer-oxygen transfer (ET/OT) mechanism as supported by the observation of products deriving from fragmentation of the corresponding radical cations in association with S-oxidation products (sulfoxides).
- Barbieri, Alessia,Di Stefano, Stefano,Lanzalunga, Osvaldo,Lapi, Andrea,Mazzonna, Marco,Olivo, Giorgio
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- Absolute rate constants for hydrogen atom transfer from tertiary amides to the cumyloxyl radical: Evaluating the role of stereoelectronic effects
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A time-resolved kinetic study of the hydrogen atom transfer (HAT) reactions from a series of alkanamides to the cumyloxyl radical (CumO?) was carried out. With N,N-dialkylformamides HAT preferentially occurs from the formyl C-H bond, while in N-formylpyrrolidine HAT mostly occurs from the ring α-C-H bonds. With the acetamides and the alkanamides almost exclusive HAT from the C-H bonds that are α to nitrogen was observed. The results obtained show that alignment between the C-H bond being broken and the amide π-system can lead to significant increases in the HAT rate constant (k H). This finding points toward the important role of stereoelectronic effects on the HAT reactivity and selectivity. The highest kH values were measured for the reactions of CumO? with N-acylpyrrolidines. These substrates have ring α-C-H bonds that are held in a conformation that is optimally aligned with the amide π-system, thus allowing for the relatively facile HAT reaction. The lowest kH value was measured for the reaction of N,N-diisobutylacetamide, wherein the steric bulk associated with the N-isobutyl groups increases the energy barrier required to reach the most suitable conformation for HAT. The experimental results are well supported by the computed BDEs for the C-H bonds of the most representative substrates.
- Salamone, Michela,Milan, Michela,Dilabio, Gino A.,Bietti, Massimo
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- Inverse axial-ligand effects in the activation of H2O 2 and ROOH by an MnIII corrolazine
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(Chemical Equation Presented) Upside-down push: Reaction of an Mn III corrolazine complex with H2O2 or ROOH leads to O-O-bond cleavage to give an MnV≡O complex (see scheme). Dramatic and unexpected axial-ligand (or "push") effects are observed, namely, the more electron-poor the axial ligand L, the faster and more heterolytic the cleavage.
- Lansky, David E.,Narducci Sarjeant, Amy A.,Goldberg, David P.
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- Carbon nanotubes as catalyst for the aerobic oxidation of cumene to cumene hydroperoxide
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The effective oxidation reaction system using the commercial carbon nanotubes (CNTs) as catalysts for the liquid aerobic oxidation of cumene to cumene hydroperoxide (CHP) under low temperature is reported in this paper. Several reaction parameters, including the temperature, catalyst content, oxygen flow rate and reaction time were carefully studied. Under optimal conditions, cumene conversion of 24.1% with CHP selectivity of 88.4%, close to that of metal catalyst, was obtained. Cumene oxidation catalyzed by CNTs was proved a radical-involved reaction, and the outstanding catalytic performance was attributed to CHP decomposition catalyzed by CNTs to produce free radicals. Oxygenated functional groups on the surface of catalyst showed a negative effect on cumene oxidation due to the localization of electrons after the introducing of defects and oxygenated functional groups. CNTs as catalysts also showed desirable recyclability after five cycling tests. This study not only provides an applicable method for selective oxidation of cumene to CHP, but also gives some useful information on catalytic role of CNTs-catalyzed liquid-phase oxidation reactions of aromatic hydrocarbons.
- Liao, Shixia,Peng, Feng,Yu, Hao,Wang, Hongjuan
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- Investigation of solvent-dependent catalytic behaviour of hydrophobic guest artificial glutathione peroxidase
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To reveal the relation between the catalytic rate of artificial glutathione peroxidase (GPx) and the property of solvent used in the determination of catalytic behaviour of glutathione peroxidase (ADA-Te-ADA) was investigated. Ethanol, DMSO, DMF and CHsu
- Yin,Wei,Shi,Shi,Hu,Jiao,Chen
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- Ruthenium Aqua Complexes Supported by the Kl?ui Tripodal Ligand: Synthesis, Structure, and Application in Catalytic C–H Oxidation in Water
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Water-soluble ruthenium(III) aqua complexes supported by the Kl?ui tripodal ligand [Co(η5-C5H5){P(O)(OEt)2}3]– (LOEt–) have been synthesized and structurally characterized, and their use as catalysts for C–H oxidation in water has been studied. The treatment of [Ru(LOEt)Cl2(MeCN)] with N-donor ligands afforded the adducts [Ru(LOEt)Cl2(L)] (L = tBuNH2 (1), pyridine (2), imidazole (3)). Refluxing [Ru(LOEt)Cl2(MeCN)] in neat tBuNH2 gave the amidine complex [Ru(LOEt)Cl2{N(H)C(Me)NHtBu}] (4). Chloride abstraction of 1–3 with AgOTs (OTs = tosylate) in 1 M p-toluenesulfonic acid afforded the water-soluble RuIII diaqua complexes [Ru(LOEt)(H2O)2(L)](OTs)2 (L= tBuNH2 (5), pyridine (6), imidazole (7)), whereas that for 4 yielded the triaqua complex [Ru(LOEt)(H2O)3](OTs)2 (8). The crystal structures of 4, 5, 7, and 8 have been determined. The reduction of 5 with Zn dust in D2O gave a diamagnetic RuII species, whereas that in MeCN led to isolation of the RuII acetonitrile complex [RuII(LOEt)(MeCN)2(tBuNH2)](PF6) (9), which has been characterized by X-ray diffraction. The RuIII aqua complexes proved to be moderately efficient catalysts for C–H bond oxidation with tert-butyl hydroperoxide in water. For example, the oxidation of ethylbenzene with tert-butyl hydroperoxide in water at room temperature in the presence of 0.1 mol-% of 8 afforded acetophenone in ca. 62 % yield.
- So, Yat-Ming,Wong, Kang-Long,Sung, Herman H. Y.,Williams, Ian D.,Leung, Wa-Hung
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- Synthesis and characterization of N3Py2 ligand-based cobalt(II), nickel(II) and copper(II) catalysts for efficient conversion of hydrocarbons to alcohols
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Three new complexes [Co(N3Py2)(H2O)](ClO4)2 1, [Ni(N3Py2)(H2O)](ClO4)2 2 and [Cu(N3Py2)](ClO4)2 3 (N3Py2 is N,N′-dimethyl-N-(2-(methyl(pyridin-2-ylmethyl)amino)ethyl)-N′-(pyridin-2-ylmethyl)ethane-1,2-diamine) have been synthesized and characterized. Non-heme ligand N3Py2 have been prepared by Eschweiler-Clarke method and reported for the first time. Compounds 1 and 2 were characterized by single crystal X-ray structure analysis. The structure of 1 and 2 revealed that Co(II) cation in 1 and Ni(II) cation in 2 are bonded to the five nitrogen atoms of N3Py2 and a water molecule thus forming an octahedral motif [M(N3Py2)(H2O)]2+. For compound 3, a square pyramidal geometry has been proposed based on the spectroscopic, elemental analysis and ESI-MS data. Compounds 1–3 were tested as catalysts in the oxidation of cumene and adamantane using m-CPBA. Comparative effect of counter anions on the product yields was observed when the perchlorates anions of 1–3 were replaced with tetraphenylborates to give compounds 1a–3a. The turnover numbers of alcohol over ketone product increased in order of catalysts, 1(1a) > 2(2a) > 3(3a).
- Narulkar, Dattaprasad D.,Srivastava, Anant Kumar,Butcher, Raymond J.,Ansy, Kanakappan M.,Dhuri, Sunder N.
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- Theoretical calculations of carbon-oxygen bond dissociation enthalpies of peroxyl radicals formed in the autoxidation of lipids
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Theoretical calculations were carried out to provide a framework for understanding the free radical oxidation of unsaturated lipids. The carbon-hydrogen bond dissociation enthalpies (BDEs) of organic model compounds and oxidizable lipids (R-H) and the carbon-oxygen bond dissociation enthalpies of peroxyl radical intermediates (R-OO.) have been calculated. The carbon-hydrogen BDEs correlate with the rate constant for propagation of free radical autoxidation, and the carbon-oxygen BDEs of peroxyl radicals correlate with rate constants for β-fragmentation of these intermediates. Oxygen addition to intermediate carbon radicals apparently occurs preferentially at centers having the highest spin density. The calculated spin distribution therefore provides guidance about the partitioning of oxygen to delocalized carbon radicals. Where the C-H BDEs are a function of the extent of conjugation in the parent lipid and the stability of the carbon radical derived therefrom, C-OO. BDEs are also affected by hyperconjugation. This gives way to different rates of β-fragmentation of peroxyl radicals formed from oxygen addition at different sites along the same delocalized radical. We have also studied by both theory and experiment the propensity for benzylic radicals to undergo oxygen addition at their ortho and para carbons which, combined, possess an equivalent unpaired electron spin density as the benzylic position itself. We find that the intermediate peroxyl radicals in these cases have negative C-OO. BDEs and, thus, have rate constants β-fragmentation that exceed the diffusion-controlled limit for the reaction of a carbon-centered radical with oxygen.
- Pratt, Derek A.,Mills, Jeremy H.,Porter, Ned A.
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- Cobalt(II) Bipyrazolate Metal-Organic Frameworks as Heterogeneous Catalysts in Cumene Aerobic Oxidation: A Tag-Dependent Selectivity
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Three metal-organic frameworks with the general formula Co(BPZX) (BPZX2- = 3-X-4,4′-bipyrazolate, X = H, NH2, NO2) constructed with ligands having different functional groups on the same skeleton have been employed as heterogeneous catalysts for aerobic liquid-phase oxidation of cumene with O2 as oxidant. O2 adsorption isotherms collected at pO2 = 1 atm and T = 195 and 273 K have cast light on the relative affinity of these catalysts for dioxygen. The highest gas uptake at 195 K is found for Co(BPZ) (3.2 mmol/g (10.1 wt % O2)), in line with its highest BET specific surface area (926 m2/g) in comparison with those of Co(BPZNH2) (317 m2/g) and Co(BPZNO2) (645 m2/g). The O2 isosteric heat of adsorption (Qst) trend follows the order Co(BPZ) > Co(BPZNH2) > Co(BPZNO2). Interestingly, the selectivity in the cumene oxidation products was found to be dependent on the tag present in the catalyst linker: while cumene hydroperoxide (CHP) is the main product obtained with Co(BPZ) (84% selectivity to CHP after 7 h, pO2 = 4 bar, and T = 363 K), further oxidation to 2-phenyl-2-propanol (PP) is observed in the presence of Co(BPZNH2) as the catalyst (69% selectivity to PP under the same experimental conditions).
- Nowacka, Anna,Vismara, Rebecca,Mercuri, Giorgio,Moroni, Marco,Palomino, Miguel,Domasevitch, Kostiantyn V.,Di Nicola, Corrado,Pettinari, Claudio,Giambastiani, Giuliano,Llabrés I Xamena, Francesc X.,Galli, Simona,Rossin, Andrea
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- Dual-site aqua mononuclear nickel(II) complexes of non-heme tetradentate ligands: Synthesis, characterization and reactivity
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Mononuclear compounds [Ni(BQCNMe2)(H2O)2](ClO4)2 1 and [Ni(BQCNH2)(H2O)2](ClO4)2 2 of N,N′-dimethyl-N,N′-di(quinolin-8-yl)cyclohexane-1,2-diamine (BQCNMe2) and N,N′-di(quinolin-8-yl)cyclohexane-1,2-diamine (BQCNH2) were synthesised and characterized by elemental analysis, IR/UV-Vis spectroscopy, cyclic voltammetry (CV)/differential pulse voltammetry (DPV) and X-ray powder pattern. [Ni(BQCNMe2)(en)](ClO4)2 3 and [Ni(BQCNMe2)(phen)](ClO4)2 4 were prepared by reacting 1 with ethylenediamine (en) and 1,10-phenanthroline (phen) respectively while [Ni(BQCNH2)(en)](ClO4)2 5 and [Ni(BQCNH2)(phen)](ClO4)2 6 were obtained from the reaction of 2. Compounds [Ni(BQENMe2)(en)](ClO4)2 7 and [Ni(BQENH2)(en)](ClO4)2.CH3CN 8 (BQENMe2 is N,N′-dimethyl-N,N′-bis(8-quinolyl)ethane-1,2-diamine) and BQENH2 is N,N′-bis(8-quinolyl)ethane-1,2-diamine) were synthesised similarly. Compounds 6 and 8 were characterized by single crystal X-ray diffractometry and their structural features are presented. The reactivity of 2 with H2O2/base was investigated. A new peak at 570 nm in the UV-Vis spectrum corresponding to 2a was obtained which on addition of 2-phenylpropionaldehyde (2-PPA) decays giving pseudo-first order rate constant of 9.2 × 10?3 s?1 and acetophenone as a major product. The catalytic hydroxylation of cumene and ethylbenzene by 1 and 2 in the presence of meta-chloroperbenzoic acid (m-CPBA) was investigated.
- Harmalkar, Sarvesh S.,Narulkar, Dattaprasad D.,Butcher, Raymond J.,Deshmukh, Mahesh S.,Kumar Srivastava, Anant,Mariappan, Mariappan,Lama, Prem,Dhuri, Sunder N.
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- Study by methods of electron spin resonance and model oxidation reaction of nanosize metal powders obtained in electric explosion of conductors
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Paramagnetic properties of nanopowders obtained by electric explosion of copper, aluminum, cobalt, and platinum conductors have been studied. The possibility of using ESR and model reaction of isopropylbenzene for testing the electric-explosion powders as
- Fedushchak,Il'ln
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- A highly efficient transformation from cumene to cumyl hydroperoxide via catalytic aerobic oxidation at room temperature and investigations into solvent effects, reaction networks and mechanisms
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Cumyl hydroperoxide (CHP) is an important intermediate for the production of phenol/acetone, but suffers from severe reaction conditions and a low yield industrially. Here, an efficient transformation from cumene to CHP was developed. Different solvents were modulated for cumene oxidation catalyzed by NHPI/Co, and reaction network and mechanisms were investigated methodically. Hexafluoroisopropanol (HFIP) markedly promoted the transformation from cumene to CHP compared to other solvents at room temperature. A cumene conversion high up to 64.3% were observed with a selectivity to CHP of 71.7%. The solvent HFIP exhibited a significant promotion on cumene oxidation due to its contribution to the enhancement of the concentration of PINO radicals. Moreover, cumyl, cumyl oxyl and methyl radicals were captured by TEMPO and analyzed by HRMS, and the reaction paths and mechanisms from cumene to products were inferred. The preparation method discovered in this work may open an access to the production of CHP.
- Chen, Chong,Ji, Lijun,Lu, Qiuting,Shi, Guojun,Yuan, Enxian,Zhou, Hongyu
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- Green method for catalyzing deprotection of tetrahydropyrane ether into hydroxyl compound
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The invention provides a green method for catalyzing deprotection of tetrahydropyrane ether into hydroxyl compound, and belongs to the field of green organic chemistry. According to the method, under neutral, open and room-temperature conditions, acetonitrile is used as a reaction solvent, FeBr2 or FeBr3 is used as a catalyst, H2O2 is used as an oxidizing agent, and a tetrahydropyrane ether derivative is converted into a hydroxyl compound within a short time. According to the invention, the catalyst FeBr2 and FeBr3, the oxidizing agent H2O2 and the solvent acetonitrile used in the method are cheap and easy to obtain, the reaction time is short, the condition is mild, the method has wide functional group compatibility, post-treatment is simple, operation is easy, and the method is a current green, environment-friendly and safe method for deprotecting the tetrahydropyrane ether derivative into the hydroxyl compound and has wide application prospects.
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Paragraph 0035-0037
(2022/03/17)
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- LIGHT INDUCED CATALYTIC C-H OXYGENATION OF ALKANES
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A method of oxygenating a benzylic C-H bond is provided. The method comprises light induced activation of an initiator and subsequent reaction with oxygen, resulting in the formation of free radicals. Subsequently, free radicals catalyze the reaction of the benzylic C-H bond with oxygen, thereby forming an oxygenated compound.
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Paragraph 00201; 00207; 00211-00217
(2021/04/02)
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- Room Temperature Aerobic Peroxidation of Organic Substrates Catalyzed by Cobalt(III) Alkylperoxo Complexes
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Room temperature aerobic oxidation of hydrocarbons is highly desirable and remains a great challenge. Here we report a series of highly electrophilic cobalt(III) alkylperoxo complexes, CoIII(qpy)OOR supported by a planar tetradentate quaterpyridine ligand that can directly abstract H atoms from hydrocarbons (R′H) at ambient conditions (CoIII(qpy)OOR + R′H → CoII(qpy) + R′?+ ROOH). The resulting alkyl radical (R′?) reacts rapidly with O2to form alkylperoxy radical (R′OO?), which is efficiently scavenged by CoII(qpy) to give CoIII(qpy)OOR′ (CoII(qpy) + R′OO?→ CoIII(qpy)OOR′). This unique reactivity enables CoIII(qpy)OOR to function as efficient catalysts for aerobic peroxidation of hydrocarbons (R′H + O2→ R′OOH) under 1 atm air and at room temperature.
- Chen, Yunzhou,Shi, Huatian,Lee, Chi-Sing,Yiu, Shek-Man,Man, Wai-Lun,Lau, Tai-Chu
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supporting information
p. 14445 - 14450
(2021/09/18)
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- Efficient oxidation of cumene to cumene hydroperoxide with ambient O2 catalyzed by metalloporphyrins
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A novel and efficient protocol for oxidation of cumene to cumene hydroperoxide was presented using ambient O2 catalyzed by very simple metalloporphyrins. The selectivity toward cumene hydroperoxide reached 98.3% in the cumene conversion of 28.1% with T(4-COOH)PPCu as a catalyst at 80°C. The origin of the higher performance of T(4-COOH)PPCu was mainly ascribed to the low catalytic performance of copper(II) in the cumene hydroperoxide decomposition, and the ability of T(4-COOH)PP in stabilizing cumene hydroperoxide through hydrogen-bond interactions between them. Compared with current industrial processes and academic research in oxidation of cumene to cumene hydroperoxide with O2, the main superiorities of this protocol were the high selectivity, high conversion, simple catalysts, solvent-free, additive-free and mild conditions which made this work an appealing reference for the industrial oxidation of cumene to cumene hydroperoxide, as well as the oxidative functionalization of other C-H bonds in various hydrocarbons. 2021 World Scientific Publishing Company.
- Shen, Hai M.,Ye, Hong L.,Wang, Qin,Hu, Meng Y.,Liu, Lei,She, Yuan B.
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p. 314 - 322
(2021/04/09)
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- Single-atom cobalt-fused biomolecule-derived nitrogen-doped carbon nanosheets for selective oxidation reactions
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Non-noble metal single-atom catalysts hold great promise in selective oxidation reactions, although the progress is still unsatisfactory because of the synthesis challenge and the lack of mechanistic interpretations. Herein, we develop a biomolecule-based strategy to synthesize isolated Co single atom site catalysts by one-step pyrolysis of guanosine and Co precursors. Due to the abundant hydrogen bonding and π-π interaction of guanosine, the as-synthesized Co-N-C catalysts present a hierarchical porous two-dimensional (2D) nanostructure with an ultrahigh specific surface area, large pore volume, and high density of cobalt single atoms. Aberration-corrected electron microscopy and X-ray photoelectron spectroscopy reveal that Co species are present as isolated single sites and stabilized by nitrogen-doped carbon nanosheets. These characteristics make Co-GS-900 suitable as an efficient catalyst for selective oxidation of aromatic alkanes. For oxidation of ethylbenzene, Co-GS-900 exhibits a superior performancefwith 91% conversion and 98% selectivity of acetophenone.
- Huang, Haitao,Wei, Qiao-Hua,Xia, Miao,Xie, Zailai,Zhang, Xuefei
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p. 14276 - 14283
(2021/07/13)
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- Palladium-Aminopyridine Catalyzed C?H Oxygenation: Probing the Nature of Metal Based Oxidant
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A mechanistic study of direct selective oxidation of benzylic C(sp3)?H groups with peracetic acid, catalyzed by palladium complexes with tripodal amino-tris(pyriylmethyl) ligands, is presented. The oxidation of arylalkanes having secondary and tertiary benzylic C?H groups, predominantly yields, depending on the substrate and conditions, either the corresponding ketones or alcohols. One of the three 2-pyriylmethyl moieties, which is pending in the starting catalyst, apparently, facilitates the active species formation and takes part in stabilization of the high-valent Pd center in the active species, occupying the axial coordination site of palladium. The catalytic, as well as isotopic labeling experiments, in combination with ESI-MS data and DFT calculations, point out palladium oxyl species as possible catalytically active sites, operating essentially via C?H abstraction/oxygen rebound pathway. For the ketones formation, O?H abstraction/в-scission mechanism has been proposed.
- Lubov, Dmitry P.,Bryliakova, Anna A.,Samsonenko, Denis G.,Sheven, Dmitriy G.,Talsi, Evgenii P.,Bryliakov, Konstantin P.
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p. 5109 - 5120
(2021/11/10)
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- Preparation method of acetophenone
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The invention provides a preparation method of acetophenone, which comprises the following steps: 1) performing oxidation treatment on an alkaline solution containing isopropylbenzene by using oxygen under a heating condition to obtain an oxidation reaction liquid. 2) The ferrous sulfate solution was added to the oxidation reaction solution for reaction to obtain acetophenone. The method has the advantages of high yield, good economic effect, low reaction cost, environment friendliness and simplicity in operation.
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Paragraph 0050-0109
(2021/12/07)
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- Hydroxylation of Unactivated C(sp3)-H Bonds with m-Chloroperbenzoic Acid Catalyzed by an Iron(III) Complex Supported by a Trianionic Planar Tetradentate Ligand
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Hydroxylation of cyclohexane with m-chloroperbenzoic acid was examined in the presence of an iron(III) complex supported by a trianionic planar tetradentate ligand. The present reaction system shows a high turnover number of 2750 with a high product selectivity of alcohol (93%). The turnover frequency was 0.51 s-1, and the second-order rate constant (k) for the C-H bond activation of cyclohexane was 1.08 M-1 s-1, which is one of the highest values among the iron complexes in the oxidation of cyclohexane so far reported. The present catalytic system can be adapted to the hydroxylation of substrates having only primary C-H bonds such as 2,2,3,3-tetramethylbutane as well as gaseous alkanes such as butane, propane, and ethane. The involvement of an iron(III) acyl peroxido complex as the reactive species was suggested by spectroscopic measurements of the reaction solution.
- Morimoto, Yuma,Hanada, Shinichi,Kamada, Ryusuke,Fukatsu, Arisa,Sugimoto, Hideki,Itoh, Shinobu
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supporting information
p. 7641 - 7649
(2021/02/03)
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- Chromoselective Photocatalysis Enables Stereocomplementary Biocatalytic Pathways**
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Controlling the selectivity of a chemical reaction with external stimuli is common in thermal processes, but rare in visible-light photocatalysis. Here we show that the redox potential of a carbon nitride photocatalyst (CN-OA-m) can be tuned by changing the irradiation wavelength to generate electron holes with different oxidation potentials. This tuning was the key to realizing photo-chemo-enzymatic cascades that give either the (S)- or the (R)-enantiomer of phenylethanol. In combination with an unspecific peroxygenase from Agrocybe aegerita, green light irradiation of CN-OA-m led to the enantioselective hydroxylation of ethylbenzene to (R)-1-phenylethanol (99 % ee). In contrast, blue light irradiation triggered the photocatalytic oxidation of ethylbenzene to acetophenone, which in turn was enantioselectively reduced with an alcohol dehydrogenase from Rhodococcus ruber to form (S)-1-phenylethanol (93 % ee).
- Schmermund, Luca,Reischauer, Susanne,Bierbaumer, Sarah,Winkler, Christoph K.,Diaz-Rodriguez, Alba,Edwards, Lee J.,Kara, Selin,Mielke, Tamara,Cartwright, Jared,Grogan, Gideon,Pieber, Bartholom?us,Kroutil, Wolfgang
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supporting information
p. 6965 - 6969
(2021/03/03)
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- To Rebound or...Rebound? Evidence for the "alternative Rebound" mechanism in Ca'H Oxidations by the systems nonheme Mn Complex/H2O2/carboxylic acid
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In this work, it has been shown that aliphatic Ca'H oxidations by bioinspired catalyst systems Mn aminopyridine complex/H2O2/carboxylic acid in acetonitrile afford predominantly a mixture of the corresponding alcohol and the ester. The alcohol/ester ratio is higher for catalysts bearing electron-donating groups at the aminopyridine core. Isotopic labeling studies witness that the oxygen atom of the alcohol originates from the H2O2molecule, while the ester oxygen comes exclusively from the acid. Oxidation of ethylbenzene in the presence of acetic acid affords enantiomerically enriched 1-phenylethanol and 1-phenyl acetate, with close enantioselectivities and the same sign of absolute chirality. Experimental data and density functional theory calculations provide evidence in favor of the rate-limiting benzylic H atom abstraction by the high-spin (S = 1) [LMnV(O)OAc]2+active species followed by competitive OH/OC(O)R rebound. This mechanism has been unprecedented for Ca'H oxidations catalyzed by bioinspired Mn complexes. The trends governing the alcohol/ester ratios have been rationalized in terms of steric properties of the catalyst, acid, and substrate. copy; 2021 American Chemical Society.
- Ottenbacher, Roman V.,Bryliakova, Anna A.,Shashkov, Mikhail V.,Talsi, Evgenii P.,Bryliakov, Konstantin P.
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p. 5517 - 5524
(2021/05/31)
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- Nonheme Diiron Oxygenase Mimic That Generates a Diferric-Peroxo Intermediate Capable of Catalytic Olefin Epoxidation and Alkane Hydroxylation including Cyclohexane
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Herein are described substrate oxidations with H2O2 catalyzed by [FeII(IndH)(CH3CN)3](ClO4)2 [IndH = 1,3-bis(2′-pyridylimino)isoindoline], involving a spectroscopically characterized (μ-oxo)(μ-1,2-peroxo)diiron(III) intermediate (2) that is capable of olefin epoxidation and alkane hydroxylation including cyclohexane. Species 2 also converts ketones to lactones with a decay rate dependent on [ketone], suggesting direct nucleophilic attack of the substrate carbonyl group by the peroxo species. In contrast, peroxo decay is unaffected by the addition of olefins or alkanes, but the label from H218O is incorporated into the the epoxide and alcohol products, implicating a high-valent iron-oxo oxidant that derives from O-O bond cleavage of the peroxo intermediate. These results demonstrate an ambiphilic diferric-peroxo intermediate that mimics the range of oxidative reactivities associated with O2-activating nonheme diiron enzymes.
- Kaizer, József,Oloo, Williamson N.,Que, Lawrence,Szávuly, Miklós
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- Enhancing Chemo- And Stereoselectivity in C-H Bond Oxygenation with H2O2by Nonheme High-Spin Iron Catalysts- And Role of Lewis Acid and Multimetal Centers
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Spin states of iron often direct the selectivity in oxidation catalysis by iron complexes using hydrogen peroxide (H2O2) on an oxidant. While low-spin iron(III) hydroperoxides display stereoselective C-H bond hydroxylation, the reactions are nonstereoselective with high-spin iron(II) catalysts. The catalytic studies with a series of high-spin iron(II) complexes of N4 ligands with H2O2 and Sc3+ reported here reveal that the Lewis acid promotes catalytic C-H bond hydroxylation with high chemo- and stereoselectivity. This reactivity pattern is observed with iron(II) complexes containing two cis-labile sites. The enhanced selectivity for C-H bond hydroxylation catalyzed by the high-spin iron(II) complexes in the presence of Sc3+ parallels that of the low-spin iron catalysts. Furthermore, the introduction of multimetal centers enhances the activity and selectivity of the iron catalyst. The study provides insights into the development of peroxide-dependent bioinspired catalysts for the selective oxygenation of C-H bonds without the restriction of using iron complexes of strong-field ligands.
- Das, Abhishek,Jana, Rahul Dev,Paine, Tapan Kanti
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supporting information
p. 5969 - 5979
(2021/05/04)
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- Fe-Catalyzed Anaerobic Mukaiyama-Type Hydration of Alkenes using Nitroarenes
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Hydration of alkenes using first row transition metals (Fe, Co, Mn) under oxygen atmosphere (Mukaiyama-type hydration) is highly practical for alkene functionalization in complex synthesis. Different hydration protocols have been developed, however, control of the stereoselectivity remains a challenge. Herein, highly diastereoselective Fe-catalyzed anaerobic Markovnikov-selective hydration of alkenes using nitroarenes as oxygenation reagents is reported. The nitro moiety is not well explored in radical chemistry and nitroarenes are known to suppress free radical processes. Our findings show the potential of cheap nitroarenes as oxygen donors in radical transformations. Secondary and tertiary alcohols were prepared with excellent Markovnikov-selectivity. The method features large functional group tolerance and is also applicable for late-stage chemical functionalization. The anaerobic protocol outperforms existing hydration methodology in terms of reaction efficiency and selectivity.
- Bhunia, Anup,Bergander, Klaus,Daniliuc, Constantin Gabriel,Studer, Armido
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supporting information
p. 8313 - 8320
(2021/03/08)
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- The influence of Fe(III) acetylacetonate and o-phenanthroline towards improvement of NHPI-catalyzed cumene oxidation
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Cumene hydroperoxide (CHP) is the most important product or intermediate in the oxidative processing of cumene. In the present study, cooperative action of NHPI catalyst with Fe(acac)3/Phen additives in oxidation of cumene has been described in terms of oxidation rate and selectivity for products, notably CHP, under variable conditions. The oxidation characteristics were influenced by promoting additives, the main function of which was to generate an active PINO radical. An abundance of the additives might enhance the non-selective conversion of intermediates and decomposition of CHP, which led to a decrease in CHP selectivity. The addition of 0.0003 mol% Fe(acac)3 was sufficient to initiate NHPI catalyzed fast cumene oxidation and very selective CHP production at 50 °°C. Phen showed an impressive multifaceted effect, as the increase in its amount initially lowered the CHP selectivity and then increased to 95% with a large excess of Phen over Fe(acac)3. That was due to the different ability of iron complexes of various compositions to react to NHPI and to CHP. UV-VIZ spectroscopy and DFT calculation was used to elucidate assistance of Phen in reduction of Fe(acac)3 with NHPI and creation of FeII/FeIII –Phen2or3 complexes as reversible single-electron carriers upon catalysis by NHPI. In addition, the selective formation of CHP contributes to the resistance of NHPI to degradation during catalysis.
- Babushkin, D. E.,Karmadonova, I. E.,Kuznetsova, L. I.,Kuznetsova, N. I.
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- Expeditious and practical synthesis of tertiary alcohols from esters enabled by highly polarized organometallic compounds under aerobic conditions in Deep Eutectic Solvents or bulk water
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An efficient protocol was developed for the synthesis of tertiary alcohols via nucleophilic addition of organometallic compounds of s-block elements (Grignard and organolithium reagents) to esters performed in the biodegradable choline chloride/urea eutectic mixture or in water. This approach displays a broad substrate scope, with the addition reaction proceeding quickly (20 s reaction time) and cleanly, at ambient temperature and under air, straightforwardly furnishing the expected tertiary alcohols in yields of up to 98%. The practicability of the method is exemplified by the sustainable synthesis of some representative S-trityl-L-cysteine derivatives, which are a potent class of Eg5 inhibitors, also via telescoped one-pot processes.
- Quivelli, Andrea F.,D'Addato, Giovanna,Vitale, Paola,García-álvarez, Joaquín,Perna, Filippo M.,Capriati, Vito
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- Ti(OiPr)4-Facilitated Formal Deoxygenative Annulation of Alkynyl 1,2-Diketones for the Synthesis of Highly Functionalized Furans
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A unique deoxygenative cyclodimerization of alkynyl 1,2-diketones facilitated by Ti(OiPr)4 is achieved, affording a series of highly functionalized furan products. An unusual C-C bond and CO bond cleavage of the substrates is observed, and Ti(OiPr)4 plays triplicate roles in the reaction. Furthermore, the products show uncommon fluorescent emission in the solid state, indicating the potential practical applications of this work.
- Lan, Shouang,Liu, Rui,Kong, Xiangwen,Liu, Jinggong,Luo, Benlong,Yang, Shuang,Fang, Xinqiang
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supporting information
p. 1504 - 1509
(2021/03/08)
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- Controlling product selectivity with nanoparticle composition in tandem chemo-biocatalytic styrene oxidation
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The combination of heterogeneous catalysis and biocatalysis into one-pot reaction cascades is a potential approach to integrate enzymatic transformations into existing chemical infrastructure. Peroxygenases, which can achieve clean C-H activation, are ideal candidates for incorporation into such tandem systems, however a constant supply of low-level hydrogen peroxide (H2O2) is required. The use of such enzymes at industrial scale will likely necessitate thein situgeneration of the oxidant from cheap and widely available reactants. We show that combing heterogeneous catalysts (AuxPdy/TiO2) to produce H2O2in situfrom H2and air, in the presence of an evolved unspecific peroxygenase fromAgrocybe aegerita(PaDa-I variant) yields a highly active cascade process capable of oxidizing alkyl and alkenyl substrates. In addition, the tandem process operates under mild reaction conditions and utilizes water as the only solvent. When alkenes such as styrene are subjected to this tandem oxidation process, divergent reaction pathways are observed due to the competing hydrogenation of the alkene by palladium rich nanoparticles in the presence of H2. Each pathway presents opportunities for value added products. Product selectivity was highly sensitive to the rate of reduction compared to hydrogen peroxide delivery. Here we show that some control over product selectivity may be exerted by careful selection of nanoparticle composition.
- Alcalde, Miguel,Brehm, Joseph,Davies, Thomas E.,Freakley, Simon J.,Harrison, Susan T. L.,Hutchings, Graham J.,Kotsiopoulos, Athanasios,Lewis, Richard J.,Morgan, David J.,Opperman, Diederik J.,Smit, Martha S.,Wilbers, Derik,van Marwijk, Jacqueline
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supporting information
p. 4170 - 4180
(2021/06/17)
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- Reduced Amino Acid Schiff Base-Iron(III) Complexes Catalyzing Oxidation of Cyclohexane with Hydrogen Peroxide
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The reduced amino acid Schiff base ligands have been prepared and were coordinated with ferric chloride to generate the iron(III) complexes. The ligands and complexes have been characterized using FT-IR, UV-vis, elemental analysis, ICP-AES analysis, mass spectra etc. After the structural characterization, these complexes were applied for the oxidation of cyclohexane using hydrogen peroxide as the oxidant under mild conditions. The activity tests showed that the L-phenylalanine-derived reduced Schiff base iron(III) complex(Ph?FeCl) afforded the highest yield of cyclohexanol and cyclohexanone(total yield up to 23.2 %). Notably, the Ph?FeCl complex catalyzes the reaction via a heterogeneous approach, allowing the complex to be separated and recycled conveniently after the oxidation reaction. Besides, the Ph?FeCl catalyst can also be extended for the selective oxidation of other alkanes and aromatics into alcohols, ketones and phenols etc. Finally, the reaction mechanism of cyclohexane oxidation on the iron(III) complex was proposed as well by the free radical inhibitors and EPR study of active intermediates.
- Zheng, Anna,Zhou, Qingqing,Ding, Bingjie,Li, Difan,Zhang, Tong,Hou, Zhenshan
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p. 3385 - 3395
(2021/08/23)
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- Formation of cobalt-oxygen intermediates by dioxygen activation at a mononuclear nonheme cobalt(ii) center
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A mononuclear nonheme cobalt(ii) complex, [(TMG3tren)CoII(OTf)](OTf) (1), activates dioxygen in the presence of hydrogen atom donor substrates, such as tetrahydrofuran and cyclohexene, resulting in the generation of a cobalt(ii)-alkylperoxide intermediate (2), which then converts to the previously reported cobalt(iv)-oxo complex, [(TMG3tren)CoIV(O)]2+-(Sc(OTf)3)n(3), in >90% yield upon addition of a redox-inactive metal ion, Sc(OTf)3. Intermediates2and3represent the cobalt analogues of the proposed iron(ii)-alkylperoxide precursor that converts to an iron(iv)-oxo intermediateviaO-O bond heterolysis in pterin-dependent nonheme iron oxygenases. In reactivity studies,2shows an amphoteric reactivity in electrophilic and nucleophilic reactions, whereas3is an electrophilic oxidant. To the best of our knowledge, the present study reports the first example showing the generation of cobalt-oxygen intermediates by activating dioxygen at a cobalt(ii) center and the reactivities of the cobalt-oxygen intermediates in oxidation reaction.
- Chandra, Anirban,Dau, Holger,Farquhar, Erik R.,Lee, Yong-Min,Malik, Deesha D.,Mebs, Stefan,Nam, Wonwoo,Ray, Kallol,Seo, Mi Sook
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supporting information
p. 11889 - 11898
(2021/09/06)
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- Efficient and selective oxidation of tertiary benzylic C[sbnd]H bonds with O2 catalyzed by metalloporphyrins under mild and solvent-free conditions
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The direct and efficient oxidation of tertiary benzylic C[sbnd]H bonds to alcohols with O2 was accomplished in the presence of metalloporphyrins as catalysts under solvent-free and additive-free conditions. Based on effective inhibition on the unselective autoxidation and deep oxidation, systematical investigation on the effects of porphyrin ligands and metal centers, and apparent kinetics study, the oxidation system employing porphyrin manganese(II) (T(2,3,6-triCl)PPMn) with bulkier substituents as catalyst, was regarded as the most promising and efficient one. For the typical substrate, the conversion of cumene could reach up to 57.6% with the selectivity of 70.5% toward alcohol, both of them being higher than the current documents under similar conditions. The superiority of T(2,3,6-triCl)PPMn was mainly attributed to its bulkier substituent groups preventing metalloporphyrins from oxidative degradation, its planar structure favoring the interaction between central metal with reactants, and the high efficiency of Mn(II) in the catalytic transformation of hydroperoxides to alcohols.
- Hu, Meng-Yun,Liu, Lei,Qi, Bei,She, Yuan-Bin,Shen, Hai-Min,Ye, Hong-Liang
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- Method for synthesizing tertiary alcohol by catalytically oxidizing benzyl tertiary C-H bonds of aromatic hydrocarbon through metalloporphyrin
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The invention discloses a method for synthesizing tertiary alcohol by catalytically oxidizing benzyl tertiary C-H bonds of aromatic hydrocarbon through metalloporphyrin. The method comprises the following steps: dispersing metalloporphyrin (1*10-1%, mol/mol) into aromatic hydrocarbon; sealing the reaction system, heating to 40-120 DEG C while stirring, introducing an oxidant (0.10-1.0 MPa), keeping the set temperature and pressure, carrying out reactions for 3.0-24.0 hours under stirring, and carrying out after-treatment on the reaction solution to obtain the product aromatic benzyl tertiary alcohol. The method has the advantages of shortest conversion path, highest atom economy, lower reaction temperature, lower environmental influence and the like, and the selectivity of aromatic benzyl tertiary alcohol is high. In addition, the content of aromatic hydrocarbon hydroperoxide is low, and the safety coefficient is high. The invention provides an efficient, feasible and safe method for synthesizing aromatic benzyl tertiary alcohol through selective catalytic oxidation of benzyl tertiary C-H bonds of aromatic hydrocarbon.
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Paragraph 0024-0089
(2020/09/30)
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- Template-free synthesis of graphene-like carbons as efficient carbocatalysts for selective oxidation of alkanes
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Selective oxidation of aromatic alkanes by C-H activation is one of the key reactions in organic synthesis and the chemical industry. Activation of C-H bonds to obtain high-value added products under mild conditions by using sustainable carbocatalysts is of particular interest. Herein, we report a sustainable, green and template-free strategy towards the fabrication of N-doped and N/S codoped carbon nanosheets by metal-free carbonization of bioprecursors guanine and guanine sulfate. The formation of thin and N/S codoped carbon nanosheets was induced by multiple interactions of the nucleobases. Benefiting from the unique textural structure of the as-synthesized carbons, including ultrathin thickness, optimal porosity, and rich structural defects, and the synergistic coupling effect of multiple dopants, the carbon nanosheets show a high catalytic performance with 85% ethylbenzene conversion and 98% selectivity to acetophenone at 80 °C after 4 h reaction, which outperforms other equivalent benchmarks (e.g. 8.5 times higher conversion and 3.2 times higher selectivity than those of oxidized carbon nanotubes). Density functional theory simulations indicate that the oxidation of ethylbenzene is catalyzed by the synergistic effect of p-N/S and g-N/S catalysts via an OH radical mechanism. This N/S codoped strategy provides guidance for the design of carbon-based catalysts for the selective oxidation of other alkanes.
- Hu, Xiang,Liu, Yuchuan,Huang, Haitao,Huang, Baobing,Chai, Guoliang,Xie, Zailai
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p. 1291 - 1300
(2020/03/11)
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- In situ synthesis of highly dispersed Co-N-C catalysts with carbon-coated sandwich structures based on defect anchoring
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Highly dispersed Co-N-C catalysts were successfully prepared via a defect strategy to anchor metal atoms with a carbon coating. The catalysts showed remarkable catalytic performance under mild conditions (a yield of 97.0% for ethylbenzene oxidation). Meanwhile, BET, TEM, XRD, Raman spectroscopy and XPS studies were employed to investigate the as-prepared catalysts. The results revealed that the unique structure was conducive to producing more defects in carbon, increasing the number of active sites and enhancing the dispersion of cobalt. The outstanding catalytic performance of the catalysts was attributed to the synergy effect of the special structure and the Co-N, pyridine nitrogen and graphite nitrogen species.
- Li, Suisheng,Zhang, Lushuang,Jie, Shanshan,Liu, Zhigang
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p. 5404 - 5409
(2020/04/17)
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- Selective oxygenation of unactivated C-H bonds by dioxygen: Via the autocatalytic formation of oxoiron(v) species
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Selective catalytic oxygenation of unactivated C-H bonds for a series of substrates by dioxygen using iron complexes was performed without the use of a co-reductant. Mechanistic studies indicate that the reaction proceeded via the autocatalytic formation of an oxoiron(v) intermediate, which brings high regioselectivity and stereoretention.
- Chandra, Bittu,De, Puja,Sen Gupta, Sayam
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supporting information
p. 8484 - 8487
(2020/08/13)
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- Method for preparing hydroxyl and trifluoromethyl substituted compounds through reaction of olefin and trifluo-romethyl bromide
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The invention discloses a method for preparing hydroxyl and trifluoromethyl substituted compounds through olefin addition reaction. According to the method, a compound containing carbon-carbon doublebonds and trifluo-romethyl bromide are taken as raw materials, a metal salt-tertiary amine system is taken as a catalyst, air is taken as an oxidizing agent, carbon-carbon double bonds can be subjected to addition reaction, and compounds with hydroxyl substitution and trifluoromethyl substitution at the same time are prepared; wherein the metal salt is one or more selected from a cobalt salt, a silver salt, a bismuth salt, a nickel salt, an iron salt or a copper salt; the tertiary amine is N-isopropyl-N-methyl-tert-butylamine or N, N-diisopropylethylamine. According to the method, the metal salt-tertiary amine system is taken as a catalyst for the first time, hydroxyl substitution and trifluoromethyl substitution of olefins are realized, one-step reaction is enough, reaction process conditions are mild, reaction raw materials are cheap and easily available, cost is low, reaction substrates have strong applicability, and can participate in the reaction as long as carbon-carbon double bonds exist in the structures, and are not influenced by substituent groups on double bond carbon atoms, and the product yield is high.
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Paragraph 0035-0039
(2020/01/14)
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- Cobalt-Tertiary-Amine-Mediated Hydroxytrifluoromethylation of Alkenes with CF3Br and Atmospheric Oxygen
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The mild and efficient hydroxytrifluoromethylation of alkenes with bromotrifluoromethane (CF3Br) and atmospheric oxygen mediated by cobalt-tertiary amine is described. This reaction proceeds with broad substrate scope and good functional group compatibility. Mechanistic studies indicate that the reaction proceeds through a radical pathway, which is enabled by combination of the previously unexplored highly efficient N-isopropyl-N,2-dimethylpropan-2-amine with Co(II) for the single electron reduction of CF3Br to CF3 radical.
- Li, Qiankun,Fan, Wu,Peng, Deqian,Meng, Bingyin,Wang, Shaohan,Huang, Rui,Liu, Shihao,Li, Suhua
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p. 4012 - 4018
(2020/05/05)
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- Reactivity and Product Analysis of a Pair of Cumyloxyl and tert-Butoxyl Radicals Generated in Photolysis of tert-Butyl Cumyl Peroxide
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Alkoxyl radicals play important roles in various fields of chemistry. Understanding their reactivity is essential to applying their chemistry for industrial and biological purposes. Hydrogen-atom transfer and C-C β-scission reactions have been reported from alkoxyl radicals. The ratios of these two processes were investigated using cumyloxyl (CumO?) and tert-butoxyl radicals (t-BuO?), respectively. However, the products generated from the pair of radicals have not been investigated in detail. In this study, CumO? and t-BuO? were simultaneously generated from the photolysis of tert-butyl cumyl peroxide to understand the chemical behavior of the pair of radicals by analyzing the products and their distribution. Electron paramagnetic resonance and/or transient absorption spectroscopy analyses of radicals, including CumO? and t-BuO?, provide more information about the radicals generated during the photolysis of tert-butyl cumyl peroxide. Furthermore, the photoproducts of (3-(tert-butylperoxy)pentane-3-yl)benzene demonstrated that the ether products were formed in in-cage reactions. The triplet-sensitized reaction induced by acetophenone, which is produced from CumO?, clarified that the spin state did not affect the product distribution.
- Oyama, Ryoko,Abe, Manabu
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p. 8627 - 8638
(2020/07/21)
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- Single-Site Cobalt-Catalyst Ligated with Pyridylimine-Functionalized Metal-Organic Frameworks for Arene and Benzylic Borylation
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We report a highly active single-site heterogeneous cobalt-catalyst based on a porous and robust pyridylimine-functionalized metal-organic frameworks (pyrim-MOF) for chemoselective borylation of arene and benzylic C-H bonds. The pyrim-MOF having UiO-68 topology, constructed from zirconium-cluster secondary building units and pyridylimine-functionalized dicarboxylate bridging linkers, was metalated with CoCl2 followed by treatment of NaEt3BH to give the cobalt-functionalized MOF-catalyst (pyrim-MOF-Co). Pyrim-MOF-Co has a broad substrate scope, allowing the C-H borylation of halogen-, alkoxy-, alkyl-substituted arenes as well as heterocyclic ring systems using B2pin2 or HBpin (pin = pinacolate) as the borylating agent to afford the corresponding arene- or alkyl-boronate esters in good yields. Pyrim-MOF-Co gave a turnover number (TON) of up to 2500 and could be recycled and reused at least 9 times. Pyrim-MOF-Co was also significantly more robust and active than its homogeneous control, highlighting the beneficial effect of active-site isolation within the MOF framework that prevents intermolecular decomposition. The experimental and computational studies suggested (pyrim?-)CoI(THF) as the active catalytic species within the MOF, which undergoes a mechanistic pathway of oxidative addition, turnover limiting σ-bond metathesis, followed by reductive elimination to afford the boronate ester.
- Akhtar, Naved,Antil, Neha,Balendra,Begum, Wahida,Kumar, Ajay,Manna, Kuntal,Newar, Rajashree,Shukla, Sakshi
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supporting information
p. 10473 - 10481
(2020/08/05)
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- C–H functionalization of alkanes, bactericidal and antiproliferative studies of a gold(III)-phenanthroline complex
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This research article demonstrates the synthesis, structural characterization, C–H functionalization, bactericidal activity and anti-proliferative studies of a mononuclear Au(III) complex, [Au(phen)Cl2]NO3 (1) [phen = 1,10-phenanthroline]. X-ray structural analysis of 1 reveals that the Au(III) complex crystallises in a monoclinic system with P21/c space group and adopts a perfect square planar geometry. The Au(III) complex has been evaluated as an efficient catalytic system towards C–H activation of a series of alkane molecules in presence of TBHP. The catalyst exhibits moderate to excellent reactivity with good selectivity toward aldehyde or ketone when aryl alkanes are used, and ketone is formed when cyclic alkanes are tested. This catalytic reaction recommends the involvement of freely diffusing hydroxyl radicals rather than metal-based oxidant for this course of catalysis. The cytotoxic activity of the Au(III) complex have been investigated against the A549 human lung cancer cell line that induces apoptosis mode of cell death and loss of mitochondrial membrane potential are prominent characteristics as an anti cancer drug as well as antibacterial activity against Staphylococcus aureus.
- Al-Hunaiti, Afnan,Balakrishnan, Gowdhami,Biswas, Bhaskar,Dey, Dhananjay,Dharumadurai, Dhanasekaran,Gopal, Vinothini,Perumalsamy, Balaji,Ramasamy, Thirumurugan
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- Regiodivergent Hydroborative Ring Opening of Epoxides via Selective C-O Bond Activation
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A magnesium-catalyzed regiodivergent C-O bond cleavage protocol is presented. Readily available magnesium catalysts achieve the selective hydroboration of a wide range of epoxides and oxetanes yielding secondary and tertiary alcohols in excellent yields and regioselectivities. Experimental mechanistic investigations and DFT calculations provide insight into the unexpected regiodivergence and explain the different mechanisms of the C-O bond activation and product formation.
- Magre, Marc,Paffenholz, Eva,Maity, Bholanath,Cavallo, Luigi,Rueping, Magnus
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supporting information
p. 14286 - 14294
(2020/09/15)
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- Isopropanol as a hydrogen source for single atom cobalt-catalyzed Wacker-type oxidation
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The first example of a heterogeneous cobalt catalytic system for Wacker-type oxidation catalyzed by a single atom dispersed Co-N/C catalyst using alcohol as the hydrogen source under an oxygen atmosphere is presented. By combining a well-designed, controlled experiment and various methods of characterization, we determined that single atom cobalt was the active center rather than nanoparticle or oxide counterparts.
- An, Yue,Chen, Bo,Gao, Shuang,Huang, Guanwang,Luo, Huihui,Shang, Sensen,Wang, Lianyue
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p. 2769 - 2773
(2020/06/17)
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- Concurrent Formation of N-H Imines and Carbonyl Compounds by Ruthenium-Catalyzed C-C Bond Cleavage of β-Hydroxy Azides
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A commercial cyclopentadienylrutenium dicarbonyl dimer ([CpRu(CO)2]2) efficiently catalyzes the formation of N-H imines and carbonyl compounds simultaneously from β-hydroxy azides via C-C bond cleavage under visible light. Density functional theory calculations for the cleavage reaction support the mechanism involving chelation of alkoxy azide species and liberation of nitrogen as the driving force. The synthetic utility of the reaction was demonstrated by a new amine synthesis promoted by chemoselective allylation of imine and synthesis of isoquinoline.
- Lee, Jeong Min,Bae, Dae Young,Park, Jin Yong,Jo, Hwi Yul,Lee, Eunsung,Rhee, Young Ho,Park, Jaiwook
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supporting information
p. 4608 - 4613
(2020/06/05)
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- METHOD FOR PRODUCING PROPYLENE OXIDE
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A method for producing propylene oxide involves an oxidation step, a distillation step, an epoxidation step, and a separation step. The distillation step involves distilling the reaction mixture containing cumene hydroperoxide to separate it into a concentrate containing cumene hydroperoxide and a distillate. The reaction mixture is continuously distilled so that the ratio of the flow rate of the distillate to the flow rate of the reaction mixture to be distilled is 0.037 to 0.13. The epoxidation step involves obtaining a reaction mixture containing propylene oxide and cumyl alcohol by contacting the concentrate with propylene in the presence of a catalyst in one or more reactors to cause a reaction between propylene and cumene hydroperoxide in the concentrate, in which the outlet temperature of the final reactor is adjusted to 115° C. or more and less than 140° C.
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Paragraph 0092-0102
(2020/05/29)
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- Benzene Hydroxylation by Bioinspired Copper(II) Complexes: Coordination Geometry versus Reactivity
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A series of bioinspired copper(II) complexes of N4-tripodal and sterically crowded diazepane-based ligands have been investigated as catalysts for functionalization of the aromatic C-H bond. The tripodal-ligand-based complexes exhibited distorted trigonal-bipyramidal (TBP) geometry (τ, 0.70) around the copper(II) center; however, diazepane-ligand-based complexes adopted square-pyramidal (SP) geometry (τ, 0.037). The Cu-NPy bonds (2.003-2.096 ?) are almost identical and shorter than Cu-Namine bonds (2.01-2.148 ?). Also, their Cu-O (Cu-Owater, 1.988 ? Cu-Otriflate, 2.33 ?) bond distances are slightly varied. All of the complexes exhibited Cu2+ → Cu+ redox couples in acetonitrile, where the redox potentials of TBP-based complexes (-0.251 to -0.383 V) are higher than those of SP-based complexes (-0.450 to -0.527 V). The d-d bands around 582-757 nm and axial patterns of electron paramagnetic resonance spectra [g∥, 2.200-2.251; A∥, (146-166) × 10-4 cm-1] of the complexes suggest the existence of five-coordination geometry. The bonding parameters showed K∥ > K∥ for all complexes, corresponding to out-of-plane πbonding. The complexes catalyzed direct hydroxylation of benzene using 30% H2O2 and afforded phenol exclusively. The complexes with TBP geometry exhibited the highest amount of phenol formation (37%) with selectivity (98%) superior to that of diazepane-based complexes (29%), which preferred to adopt SP-based geometry. Hydroxylation of benzene likely proceeded via a CuII-OOH key intermediate, and its formation has been established by electrospray ionization mass spectrometry, vibrational, and electronic spectra. Their formation constants have been calculated as (2.54-11.85) × 10-2 s-1 from the appearance of an O (π?σ) → Cu ligand-to-metal charge-transfer transition around 370-390 nm. The kinetic isotope effect (KIE) experiments showed values of 0.97-1.12 for all complexes, which further supports the crucial role of Cu-OOH in catalysis. The 18O-labeling studies using H218O2 showed a 92% incorporation of 18O into phenol, which confirms H2O2 as the key oxygen supplier. Overall, the coordination geometry of the complexes strongly influenced the catalytic efficiencies. The geometry of one of the CuII-OOH intermediates has been optimized by the density functional theory method, and its calculated electronic and vibrational spectra are almost similar to the experimentally observed values.
- Anandababu, Karunanithi,Mayilmurugan, Ramasamy,Muthuramalingam, Sethuraman,Velusamy, Marappan
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p. 5918 - 5928
(2020/04/20)
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- Method for selectively oxidizing cumene compounds
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The invention relates to a method for selectively oxidizing cumene compounds, and the method comprises the following steps: placing cumene compounds shown in a formula (I), an iron porphyrin catalyst,an oxidant and a dispersant into a ball milling tank, sealing the ball milling tank, performing ball milling for 3 to 24 hours at a rotating speed of 100 to 800 rpm at room temperature, stopping ballmilling once every 1 to 3 hours in the ball milling process, discharging gases in the ball milling tank, finishing the reaction, and performing post-treatment on a reaction mixture to obtain product2-phenyl-2-propanol compound shown in a formula (II); according to the invention, the oxidation conversion of the cumene and derivatives thereof is realized through solid-phase ball milling, the reaction mode is novel, the operation is convenient, and the energy consumption is low; the method needs no organic solvent, thus effectively avoiding the use of toxic and harmful organic solvents and being green and environment-friendly; has low peroxide content and high safety factor, and high 2-phenyl-2-propanol and derivative selectivity and meets the social requirements of the current green chemical process, environmental compatibility chemical process and biological compatibility chemical process.
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Paragraph 0043-0044; 0057-0058; 0065-0066
(2019/11/21)
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- Method for preparing alpha, alpha-dimethyl benzyl alcohol under dual catalyst and solvent-free conditions
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The present invention relates to a method for preparing alpha, alpha-dimethyl benzyl alcohol under dual catalyst and solvent-free conditions. The method comprises the following steps of 1) preparing an ionic liquid catalyst; 2) adding cumene, the ionic liquid catalyst and an inorganic salt catalyst into a reactor with a reflux device, introducing a certain amount of air into the reactor as an oxygen source, and enabling cumene to perform an oxidation reaction under a solvent-free condition; and 3) after the reaction is finished, performing standing, wherein after the material in the reactor islayered, the upper-layer material is a reaction product alpha-dimethyl benzyl alcohol and the lower-layer material is a mixed catalytic system formed by the ionic liquid catalyst and the inorganic salt catalyst; and 4) separating the upper-layer material to obtain the reaction product alpha-dimethyl benzyl alcohol. The method is a brand-new synthesis mechanism, is low in cost and is suitable forlarge-scale industrial production.
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Page/Page column 6-9
(2019/12/31)
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- Bicontinuous mesoporous Co, N co-doped carbon catalysts with high catalytic performance for ethylbenzene oxidation
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A series of bicontinuous mesoporous Co, N co-doped carbon catalysts (Co-N-C), which have large pore sizes and high specific surface areas with remarkable catalytic activity, were prepared through a method using KIT-6 silica as a hard template, and cobalt porphyrin and sucrose as precursors. And morphological and structural characterizations were performed using N2 adsorption-desorption isotherm, XRD, Raman, TEM and XPS techniques. The results showed that the ethylbenzene oxidation with TBHP as an oxidant over the bicontinuous mesoporous Co, N co-doped carbon catalysts achieved 93% of ethylbenzene conversion with about 99% of selectivity to acetophenone. The superior catalytic performance of the catalysts was attributed to the synergistic effect of factors such as high surface area and well-dispersed metal active sites.
- Zhang, Lushuang,Jie, Shanshan,Liu, Zhigang
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supporting information
p. 7275 - 7281
(2019/05/24)
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- Iron complex containing meta-carborane triazole ligand, preparation and application thereof
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The invention relates to an iron complex containing a meta-carborane triazole ligand, preparation and application thereof. The preparation method of the iron complex includes the steps of: 1) adding an n-BuLi solution into a meta-carborane solution, and then carrying out reaction at room temperature for 30-60min; 2) adding 3-propargyl bromide, carrying out reaction at room temperature for 2-4h, then pumping out the solvent, and carrying out recrystallization to obtain 1, 3-dipropargyl meta-carborane; 3) dissolving 1, 3-dipropargyl meta-carborane, aryl azide and a catalyst in an organic solvent, and then carrying out reaction at room temperature for 3-6h; and 4) adding FeCl2, carrying out reaction at room temperature for 5-8h, and then performing separation. The iron complex is used for catalytic oxidation of aromatic hydrocarbon to synthesize aromatic alcohol. Compared with the prior art, the invention adopts one-pot method to obtain the iron complex containing the meta-carborane triazole ligand, the synthesis process is simple and green, and the iron complex can achieve efficient catalytic oxidation of aromatic hydrocarbon to prepare an aromatic alcohol compound under the condition that hydrogen peroxide serves as an oxidizing agent.
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Paragraph 0097-0100
(2020/01/12)
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- The selective oxidation of hydrocarbons on isolated iron active sites under ambient conditions
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The N-doped carbon material supported Fe catalysts were developed for the oxidation of C-H bond of hydrocarbons to ketones and alcohols. The supported Fe catalysts were prepared by pyrolysis of [CMIM]3Fe(CN)6 ionic liquid in activated carbon. And the Fe(Ⅲ)?CN-600 showed good activity and high selectivity for the oxidation of alfa C-H bond of alkylbenzenes. The isolated Fe(Ⅲ) iron active sites should be responsible for the high activity and selectivity for the oxidation of hydrocarbons to ketones. Several ketones were obtained in good to excellent yields. Moreover, cyclohexanone can also be obtained through the oxidation of cyclohexane.
- Qi, Zhengliang,Liu, Junmei,Guo, Wanwan,Huang, Jun
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p. 946 - 955
(2020/01/08)
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- Directed: Ortho-metalation-nucleophilic acyl substitution strategies in deep eutectic solvents: The organolithium base dictates the chemoselectivity
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Directed ortho metalation (DoM) or nucleophilic acyl substitution (SNAc) can be efficiently programmed on the same aromatic carboxylic acid amide, in a choline chloride-based eutectic mixture, by simply switching the nature of the organolithium reagent. Telescoped, one-pot ortho-lithiation/Suzuki-Miyaura cross-couplings have also been demonstrated for the first time in Deep Eutectic Solvents.
- Ghinato, Simone,Dilauro, Giuseppe,Perna, Filippo Maria,Capriati, Vito,Blangetti, Marco,Prandi, Cristina
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p. 7741 - 7744
(2019/07/12)
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- Oxygenation of styrenes catalyzed by N-doped carbon incarcerated cobalt nanoparticles
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NCI-Co catalyzed olefin oxygenation reactions were investigated. Among the metals examined, including noble metals, the reaction proceeded specifically on Co catalysts, and nitrogen dopant was crucial for the catalytic activity. The presence of NaBH4 as a hydride source, the corresponding alcohols were obtained in high yields. The substrates bearing a reductant-sensitive functional group were made tolerant by changing the reductant and using an additive, and furthermore, the corresponding ketones were accessed by changing reaction conditions. A preliminary examination of other SOMOphiles suggested that the heterogeneous catalyst systems have the potential to be applied to more general hydrofunctionalization of olefins to form various kinds of bonds. Several mechanistic studies suggested that the reaction proceeded in a heterogeneous manner and formed a radical intermediate on cobalt nanoparticle species.
- Yasukawa, Tomohiro,Kobayashi, Shū
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supporting information
p. 1980 - 1985
(2019/12/24)
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- Carbon Dioxide-Mediated C(sp2)-H Arylation of Primary and Secondary Benzylamines
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C-C bond formation by transition metal-catalyzed C-H activation has become an important strategy to fabricate new bonds in a rapid fashion. Despite the pharmacological importance of ortho-arylbenzylamines, however, effective ortho-C-C bond formation of free primary and secondary benzylamines using PdII remains an outstanding challenge. Presented herein is a new strategy for constructing ortho-arylated primary and secondary benzylamines mediated by carbon dioxide (CO2). The use of CO2 with Pd is critical to allowing this transformation to proceed under relatively mild conditions, and mechanistic studies indicate that it (CO2) is directly involved in the rate-determining step. Furthermore, the milder temperatures furnish free amine products that can be directly used or elaborated without the need for deprotection. In cases where diarylation is possible, an interesting chelate effect is shown to facilitate selective monoarylation.
- Kapoor, Mohit,Chand-Thakuri, Pratibha,Young, Michael C.
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supporting information
p. 7980 - 7989
(2019/05/22)
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- Hafnium Triflate as a Highly Potent Catalyst for Regio- and Chemoselective Deprotection of Silyl Ethers
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As a Group IVB transition metal Lewis acid, hafnium triflate [Hf(OTf) 4 ] exhibited exceptionally high potency in desilylations. Since the amounts of Hf(OTf) 4 required for the deprotection of 1°, 2°, 3° alkyl and aryl tert -butyldimethylsilyl (TBS) ethers are significantly different, ranging from 0.05 mol% to 3 mol%, regioselective deprotection of TBS could be easily implemented. Moreover, chemoselective cleavage of different silyl ethers or removal of TBS in the presence of most hydroxyl protecting groups was also accomplished. NMR analyses of silyl products from TBS deprotection indicated that Hf(OTf) 4 -catalyzed desilylation may proceed via different mechanisms, depending on the solvent used.
- Zheng, Xiu-An,Kong, Rui,Huang, Hua-Shan,Wei, Jing-Ying,Chen, Ji-Zong,Gong, Shan-Shan,Sun, Qi
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supporting information
p. 944 - 953
(2019/02/10)
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- Hafnium trifluoromethanesulfonate catalyzed silyl ether protecting group removing method
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The invention provides a hafnium trifluoromethanesulfonate catalyzed silyl ether protecting group removing method. Various silyl ether protecting groups of nearly 50 kinds of substrates can be efficiently removed in 0.5-16 hours at room temperature by taking 0.02mol%-0.3mol% hafnium trifluoromethanesulfonate as a catalyst, a silyl ether protected hydroxyl compound as a substrate and conventional AR methanol as a solvent. 42 kinds of silyl ether protecting group removing products can be obtained at high yield by performing conventional slica column chromatography purification on a crude product. By regulating the use amount of the catalyst, the Hf(OTf)4 catalyst can realize regioselective removal of 1-degree, 2-degree and 3-degree alkyl TBS and aryl TBS protective groups. Moreover, in a proper equivalent scope, the Hf(OTf)4 catalyst can also realize 1) chemoselective removal of different kinds of silica-based protective groups; and 2) chemoselective removal of 1-degree TBS protective groups under the condition of not affecting a majority of common hydroxyl protective groups.
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Paragraph 0009; 0014
(2019/01/21)
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