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A facile preparation method of nano-CuO catalysts, assembled in the hollow nanotube of halloysite nanotubes (HNTs), was developed. The characterizations of XRD, TEM, SEM, BET, XRF and FT-IR were used to analyze the structure and properties of the nano-CuO

The copper complexes [Cu(4-MeBPI)(OAc)] (4), [Cu(4-Me-10-tBuBPI)(OAc)] (5) and [Cu(BTI)(OAc)] (6) [BPI = 1,3-bis(2-pyridylimino)isoindole, BTI = 1,3-bis(2-thiazolylimino)isoindole] were prepared by reaction of the protio ligands with copper(II) acetate. Compounds 4 and 6 were characterized by X-ray diffraction, establishing distorted square-planar coordination geometries of the copper ions. Two monoclinic modifications of 6 (6a and 6b) were found, both crystallizing in the space group P21/c, but possessing different cell parameters. In contrast to 6a, which is monomeric in the crystal, the second monoclinic modification 6b has a more complicated crystal structure, which is composed of both monomeric complex units such as those found in 6a and infinite chains of coordination polymers. The copper atoms in the polymeric chains of 6b display fivefold coordination and a ligand polyhedron that is an intermediate form between a trigonal-bi-pyramidal and a square-pyramidal geometry. The allylic peroxylation of cyclohexene with tBuOOH (70% aqueous solution) catalyzed by 4 and 6 (0.17 mol %) gave tert-butylperoxy-3-cyclohexene with selectivities of 86% and 80% (based on cyclohexene) and turnover frequencies of 63 h -1 and 18 h-1, respectively. The peroxylation reaction is thought to proceed according to a Haber-Weiss radical chain mechanism. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

In continuing our studies on the photosensitizing ability of the 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) molecular complex of meso-tetraphenylporphyrin, we have studied the photocatalytic activity of tetracyanoethylene (TCNE) molecular complexes o

In short-time-heated mixtures of lactose and Nα-acetyllysine 1-[N∈-(N α-acetyllysinyl)]-1,2-dehydro1,4-dideoxy-3-hexulose (C6-AR) is formed as main product, whereas 3-hydroxy-4-(alkylamino)-3-buten-2-one (C

A novel biomimetic method for rapid oxidation of a wide range of benzylic, allylic, aliphatic, primary and secondary alcohols to the related aldehydes and ketones using Bu4NHSO5 catalyzed by Mn(TPP)OAc/pyridine system with high to ex

The hybrid complex consist of molybdenylacetylacetonate complex covalently linked to a lacunary Keggin-type polyoxometalate, K8[SiW11O39] (POM), was synthesized and characterized by elemental analysis, SEM, XRD, diffuse re

A new dimeric copper complex namely, [Cu2(PDA)2(Ald)2(H2O)2]·8H2O, 1, (where PDA = 2,4-pyridine dicarboxylic acid, Ald = aldrithiol) has been synthesized through a slow diffusion technique.

The selective liquid phase oxidation of cyclohexene to 2-cyclohexe-1-one and 1,2-cyclohexanediol has been investigated over gold nanoparticles (GNPs) with molecular oxygen in a solvent-free condition. The gold nanoparticles were immobilized on thiolated chitosan derivative (TChD), by grafting thiol groups on the support. The catalyst was characterized by XPS, N2 adsorption/desorption, TEM, FT-IR and UV-vis spectroscopy. TEM results show that the majority of Au particles have diameters in the range of 3-6 nm. X-ray photoelectron spectroscopy (XPS) revealed the coexistence of both oxidized and metallic gold species on the surface of TChD. The results show that the catalytic performance of GNPs/TChD is quite remarkable and the catalytic activity over recycled catalyst remains at a high level after at least 4 cycles. Activity tests were carried out in an autoclave at 80 C without any solvent. In order to obtain maximum conversion, the reaction parameters such as reaction temperature and time were optimized. Under optimized conditions, a maximum of 87% conversion and 70% selectivity was achieved with the GNPs/TChD catalyst.

Azo linked Schiff-base[L] complexes of Mn(II)(1), Cu(II)(2) and Co(II)(3) obtained by template method, in the reaction of 4-(benzeneazo) salicylaldehyde with 1,2-propanediamine in the present of metal acetate, respectively. Complexes are used as catalyst

We present a novel strategy for preparing silylated MgAl layered double hydroxide (LDH) intercalated with metal complexes with the purpose of improving the catalytic activity of the intercalated active species. This strategy involves preparing the exfolia

In order to overcome problems associated with the use of porphyrins under photooxidative conditions, the 1 : 2 molecular complex of meso-tetraphenylporphyrin (H2TPP) with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) has been used as a photos

Silyloxycyclopropanes are easily oxidized by eerie ammonium nitrate to generate β-carbonylalkyl radicals which are able to add to 1,3-butadiene to give a mixture of 4-(γ-carbonylalkyl)-substituted 3-nitroxy-1-butenes and 4-(γ-carbonylalkyl) substituted (E)-1-nitroxy-2-butenes (1,2- and 1,4-adducts) in ca. 1:1 molar ratio. The crude mixture, subjected to palladium-catalyzed alkylation by a variety of carbon nucleophiles, affords mainly δ,g3-unsaturated carbonyl compounds with high regio- and stereoselectivity and in satisfactory overall yield.

An oxidant in heterogeneous system was obtained by impregnating Zr(OH)4 with NH4VO3 followed by calcination in air at 500 deg C; this material (V2O5/ZrO2) converted alcohols into the corresponding aldehydes or ketones at moderate temperatures in solvent.

It has been revealed that the generation of 2-cyclohexenones from cis- 1,4-dihydroxycyclohexene derivatives under PdCl2(PPh3)2-HCO2NH4 system takes place in an intramolecular pathway involving unprecedented mode of suprafacial 1,4-hydrogen migration across the 1,4-allylic centers.

X-ray crystallographic structure analysis showed that a molecule of 2-benzoylcyclohexanone (2), which undergoes an efficient Type II reaction in solution but not in the crystalline state, is in a keto and chair form with an equatorial benzoyl group. Irradiation of 3-benzoylcyclohexanone (3) gives 7-phenylhepten-4,7-dione (4, 61%) and a mixture of cyclization products 5 (25%). High photoreactivity of 2 and 3 is caused by the efficient cyclohexanone ring inversion. Upon irradiation, 2-(benzoylmethyl)cyclohexanone (6) gives acetophenone (7), 2-cyclohexenone (8) and the cyclobutanol 9 in 59, 59 and 35% yield, respectively, and 1-phenyl-3-propylpentan-l,4-dione (10) gives 7 and the cyclobutanol 11 in 73 and 4% yield, respectively. The quantum yields for the disappearance of 6 and 10 are 0.68 and 0.67, respectively. Irradiation of 2-(benzoylmethyl)-2-ethoxycarbonylcyclohexanone (12) gives 7 and the cyclobutanol 13 in 46 and 51 % yield, respectively. The quantum yield for the disappearance of 12 is 1.00, so that reverse hydrogen transfer is suppressed by intramolecular hydrogen bonding in the 1,4-biradical intermediate. When 6 is irradiated on a dry silica gel surface, the Type II reaction occurs to give 7, 8 and 9 in 38, 38 and 43% yield, respectively. The cyclization in the photoreaction of (benzoylmethyl)cyclohexane also increases from 68% in benzene to 81% on a dry silica gel surface. Restriction of conformational change in the 1,4-biradical is an important factor for the cyclization. Copyright

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In this study, a series of meso-tetraarylporphyrins (aryl = phenyl, 2-methylphenyl and 2-chlorophenyl), H2T(aryl)P immobilized on nanosized Amberlyst-15 (nanoAmb) through the acid-base reaction were utilized as highly efficient (turnover number

The development of catalytic aerobic epoxidation by numerous metal complexes in the presence of aldehyde as a sacrificial reductant (Mukaiyama epoxidation) has been reported, however, comprehensive examination of oxygen atom transfer mechanism involving free radical and highly reactive intermediates has yet to be presented. Herein, meso-tetrakis(pentafluorophenyl) porphyrinatooxidovanadium(IV) (VOTPFPP) was prepared and proved to be efficient toward aerobic olefin epoxidation in the presence of isobutyraldehyde. In situ electron paramagnetic resonance spectroscopy (in situ EPR) showed the generation, transfer pathways and ascription of free radicals in the epoxidation. According to the spectral and computational studies, the side-on vanadium-peroxo complexes are considered as the active intermediate species in the reaction process. In the cyclohexene epoxidation catalyzed by VOTPFPP, the kinetic isotope effect value of 1.0 was obtained, indicating that epoxidation occurred via oxygen atom transfer mechanism. The mechanism was further elucidated using isotopically labeled dioxygen experiments and density functional theory (DFT) calculations.

Allylic oxidation of cycloalkenes is a promising route to generate α,β-unsaturated ketones but encounters difficulties in selectivity control. Here, it is demonstrated that ruthenium nanoparticles (1–2?nm sized) decorated on TiO2 nanomaterials with different morphologies (nanoparticles, nanotubes and nanofibers) are demonstrated highly efficiency and selectivity for the selective aerobic oxidation of cyclohexene and indane. The as-prepared Ru/TiO2 nanofibers (NFs) represents higher activity for the allylic oxidation of cyclohexene (conv. 95%) with 78% selectivity toward 2-cyclohexen-1-one at 75?°C under 4?bar O2. Whereas, Ru/TiO2 nanoparticles (NPs) and Ru/TiO2 nanotubes (NTs) show 92 and 84% conversion, respectively. Upon switching to Al2O3 support, catalytic activity with Ru/Al2O3 is decreased significantly to 27%. Very high activity for indane (conv. 70%) toward 2,3-dihydro-1H-inden-1-one (selectivity 85%) has also been observed by using Ru/TiO2 NFs. Ru/TiO2 nanomaterials possess higher catalytic efficiency as compared to Ru NPs and TiO2 nanomaterials individually, representing a positive synergetic effect. Moreover, these reported results suggest that the higher activities of Ru/TiO2 NPs and Ru/TiO2 NFs are related to the crystalline structure, pore volume and surface area of the supports. Graphical Abstract: [Figure not available: see fulltext.]

Hypervalent iodine(V) reagents are a powerful class of organic oxidants. While the use of I(V) compounds Dess-Martin periodinane and IBX is widespread, this reagent class has long been plagued by issues of solubility and stability. Extensive effort has been made for derivatizing these scaffolds to modulate reactivity and physical properties but considerable room for innovation still exists. Herein, we describe the preparation, thermal stability, optimized geometries, and synthetic utility of an emerging class of I(V) reagents, Bi(N)-HVIs, possessing datively bound bidentate nitrogen ligands on the iodine center. Bi(N)-HVIs display favorable safety profiles, improved solubility, and comparable to superior oxidative reactivity relative to common I(V) reagents. The highly modular synthesis and in situ generation of Bi(N)-HVIs provides a novel and convenient screening platform for I(V) reagent and reaction development.

Electrochemical techniques have long been heralded for their innate sustainability as efficient methods to achieve redox reactions. Carbonyl desaturation, as a fundamental organic oxidation, is an oft-employed transformation to unlock adjacent reactivity through the formal removal of two hydrogen atoms. To date, the most reliable methods to achieve this seemingly trivial reaction rely on transition metals (Pd or Cu) or stoichiometric reagents based on I, Br, Se or S. Here we report an operationally simple pathway to access such structures from enol silanes and phosphates using electrons as the primary reagent. This electrochemically driven desaturation exhibits a broad scope across an array of carbonyl derivatives, is easily scalable (1–100 g) and can be predictably implemented into synthetic pathways using experimentally or computationally derived NMR shifts. Systematic comparisons to state-of-the-art techniques reveal that this method can uniquely desaturate a wide array of carbonyl groups. Mechanistic interrogation suggests a radical-based reaction pathway. [Figure not available: see fulltext.]

The epoxidation of olefin as a strategy to protect carbon-carbon double bonds is a well-known procedure in organic synthesis, however the reverse reaction, deprotection/deoxygenation of epoxides is much less developed, despite its potential utility for the synthesis of substituted olefins. Here, we disclose a clean protocol for the selective deprotection of epoxides, by combining commercially available organophosphorus ligands and gold nanoparticles (Au NP). Besides being successfully applied in the deoxygenation of epoxides, the discovered catalytic system also enables the selective reduction N-oxides and sulfoxides using molecular hydrogen as reductant. The Au NP catalyst combined with triethylphosphite P(OEt)3 is remarkably more reactive than solely Au NPs. The method is not only a complementary Au-catalyzed reductive reaction under mild conditions, but also an effective procedure for selective reductions of a wide range of valuable molecules that would be either synthetically inconvenient or even difficult to access by alternative synthetic protocols or by using classical transition metal catalysts. This journal is

A new heterogeneous catalytic system consisting of cobalt nanoparticles (CoNPs) supported on MgO and tert-butyl hydroperoxide (TBHP) as oxidant is presented. This CoNPs@MgO/t-BuOOH catalytic combination allowed the epoxidation of a variety of olefins with good to excellent yield and high selectivity. The catalyst preparation is simple and straightforward from commercially available starting materials and it could be recovered and reused maintaining its unaltered high activity.

The present invention provides a process for preparing cycloalkane diols. In detail, the process for preparing cycloalkane diols of the present invention comprises contacting a gaseous oxidizer and cycloalkene with MIL metal - organic frameworks to produce cycloalkane diols.

Two isostructural lanthanide metal-organic frameworks (Ln-MOF-589, Ln = La3+, Ce3+), constructed from a tetratopic linker, benzoimidephenanthroline tetracarboxylic acid (H4BIPA-TC), have been solvothermally synthesized and characterized. These Ln-MOF-589 materials consist of Lewis acid [Ln2(-COO)6(-COOH)2(H2O)6] units and a naphthalene diimide core, which exhibited promising catalytic activity for the oxidation of olefins. Among them, Ce-MOF-589 exhibited outstanding performance with high conversions of styrene and cyclohexene (94 and 90%, respectively), and good selectivities towards styrene oxide and 2-cyclohexen-1-one (85, and 95%, respectively). Notably, the catalytic activity of Ce-MOF-589 outperformed that of homogeneous and heterogeneous catalysts, and representative MOFs. Also, Ce-MOF-589 can be recycled for at least up to six cycles with no significant loss of catalytic performance.

Abstract: To avoid the aggregation problem and activity loss of nickel oxide (NiO) nanoparticles (NPs) in organic reactions, NiO NPs were incorporated into TUD-1 mesoporous material. One-step sol–gel preparation was applied to prepare four samples of Ni incorporated in TUD-1 silica matrix with different Ni content. The four samples with Si/Ni ratio = 100, 50, 20, and 10 were characterized by means of elemental analysis, powder X-ray diffraction (XRD), Raman spectroscopy, N2 sorption measurements, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and high-resolution transmission electron microscopy (HR-TEM). The characterization analysis showed that Ni2+ ions were incorporated into the silica matrix as individual isolated active sites at Ni content smaller than 2 wt%, and as nanoparticles of NiO when the loading is equal to or higher than 5 wt%. The size of NiO NPs inside the silica matrix is highly dependent on the Ni content, i.e. the size of NiO NPs when the loading was 5 wt% and 10 wt% was 5–10 and 40–60?nm, respectively. The catalytic activity of Ni-TUD-1 was investigated in the epoxidation reaction of cyclohexene at room temperature by using meta-chloroperoxybenzoic acid (m-CPBA) as an oxidant. The obtained results showed that Ni-TUD-1 exhibited superior activity in which 100% conversion of cyclohexene with > 90% selectivity towards cyclohexene oxide was obtained instantly. This result was found to benchmark not only the unsupported NiO nanoparticles, but also the reported catalysts at similar conditions. Graphic Abstract: [Figure not available: see fulltext.].

Utilization of metal-organic frameworks as heterogeneous catalysts is crucial owing to their abundant catalytic sites and well-defined porous structures. Highly robust [Cu3(trz)3(μ3-OH)(OH)2(H2O)4]·2H2O (trz = 1,2,4-triazole) was employed as a catalyst for liquid-phase cyclohexene oxidation with hydrogen peroxide (H2O2). Possessing the porous structure together with Lewis acid attributes from the triangular [Cu3(trz)3(μ3-OH)] center, selective oxidation of cyclohexene to allylic products gives a molar yield of 31% with 87% selectivity. According to the highly selective allylic production, the reaction over the present Cu-MOF plausibly occursviahomolytic activation of H2O2. This finding elucidates the unique features of the MOF for efficient catalysis of cyclohexene oxidation.

A series of Mo-containing MFI zeolites with different Mo loadings (Mo-MFI-n, n represent the initial Si/Mo molar ratio) was hydrothermally synthesized by using tetrapropylammonium hydroxide as the template and Mo-EDTA complex as the Mo source. Various characterization results demonstrated that the use of the Mo-EDTA complex is beneficial for the incorporation of more Mo species into the MFI-type zeolites. The special complexing capability of EDTA2– plays a critical role in adjusting the release rate of the Mo species to combine with the Si tetrahedron species during the zeolite growth process, thus leading to a uniform distribution of Mo in the MFI framework. In addition, a small portion of extra-framework Mo clusters may be distributed inside the channels or near the pore window of the zeolites. The catalytic properties of these Mo-containing MFI zeolites were evaluated for the epoxidation of cyclohexene with H2O2 as the oxidant. The composition-optimized catalyst, Mo-MFI-50, efficiently converted cyclohexene to the corresponding epoxide with a relatively high conversion (93%) and epoxide selectivity (82%) at 75 °C after 9 h of reaction. Moreover, the resultant Mo-containing MFI catalyst exhibited excellent structural stability and recoverability and was easily recycled by simple filtration without the need for calcination treatment.

Catalytic oxidation of organic substrates has wide applications in chemical industries due to which huge extensive research work is continuously going on throughout the world. Present study reports efficacious use of Trans (Cl)-2,2′-bipyridinedicarbonyldichlororuthenium(II) complex catalyzed oxidation of internal and terminal olefins, aryl hydrocarbons and alcohols. CH2Cl2–C2H5OH (6:4) was suitable solvent system for these oxidation reactions. The normal pressure oxidation reaction has been carried out at 1 ?atm. Pressure of oxygen and at 300C. The high pressure oxidation reaction was done at 4.48 ?× ?103 KNm3 pressure of oxygen and at 600C. No diminished catalytic activity was observed while checking the recyclability of catalyst up to 6–8 catalytic runs. Catalytic activity was also investigated using tert-butyl hydroperoxide as oxidant inspite of di-oxygen. Effect of different parameters on the rate of oxidation was also studied i.e. extra ligand, temperature, solvents, acids and bases. Kinetic studies have been done and on the basis of kinetics, the mechanism is proposed.

Two novel manganese (III) and iron (III) complexes of an N,N-bis(1-naphthalidimine)-o phenylene diamine ligand have been successfully synthesized and characterized by various analytical techniques including single crystal X-ray structure analysis. The lig

In this research, β-tetra-brominated meso-tetraphenylporphyrinatomanganese(III) acetate [MnTPPBr4(OAc)] (MnPor) was anchored onto a magnetite imidazole-modified graphene oxide nanosheet (Fe3O4.GO.Im). The obtained catalyst (Fe3O4.GO.Im@MnPor) was characterized through Fourier transform infrared (FT-IR) and diffuse reflectance UV–Visible spectrophotometry (DR UV–Vis), powder X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, thermogravimetric analysis (TGA) and atomic absorption spectroscopy. The characterization was performed to determine the amount of manganese porphyrin loaded on the GO support. The new immobilized catalyst was employed for the efficient epoxidation of different alkenes with urea hydrogen peroxide (UHP) and acetic acid (HOAc) as oxidant activators under mild conditions. Olefins were oxidized efficiently to their corresponding epoxide with 63–100% selectivity in the presence of Fe3O4.GO.Im@MnPor. Moreover, an remarkable turnover frequency (93) was achieved for the oxidation of α-pinene. The graphene oxide-bound Mn-porphyrin was recovered from the reaction mixture by magnetic decantation and reused several times. Graphic Abstract: [Figure not available: see fulltext.]

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.

A novel Se-doped silica material was fabricated, and this easily prepared material could be used as an efficient recyclable catalyst for β-ionone oxidation. Interestingly, by doping with fluorine in the catalyst, the reaction selectivity was significantly enhanced to produce the important pharmaceutical intermediate β-ionone epoxide selectively. Characterization of the materials indicated that by doping with F, the electropositivity of the catalytic Se species was obviously enhanced due to the strong electron-withdrawing features of F, and this was a key factor for controlling the reaction selectivity in the β-ionone epoxidation reaction. The electropositivity of a silica support might also increase and the reinforced electropositivity of Si sites might be beneficial for the adsorption of a β-ionone substrate and for the contact of the electron-enriched endocyclic C-C with the catalyst.

Processes for converting an olefin reactant into a diol compound are disclosed, and these processes include the steps of contacting the olefin reactant and a supported chromium catalyst comprising chromium in a hexavalent oxidation state to reduce at least a portion of the supported chromium catalyst to form a reduced chromium catalyst, and hydrolyzing the reduced chromium catalyst to form a reaction product comprising the diol compound. While being contacted, the olefin reactant and the supported chromium catalyst can be irradiated with a light beam at a wavelength in the UV-visible spectrum. Optionally, these processes can further comprise a step of calcining at least a portion of the reduced chromium catalyst to regenerate the supported chromium catalyst.

Mn and Fe BPMEN complexes showed excellent reactivity in catalytic oxidation with an excess of co-reagent (CH3COOH). In the straight line of a cleaner catalytic system, volatile acetic acid was replaced by SiO2 (nano)particles with two different sizes to which pending carboxylic functions were added (SiO2@COOH). The SiO2@COOH beads were obtained by the functionaliza-tion of SiO2 with pending nitrile functions (SiO2@CN) followed by CN hydrolysis. All complexes and silica beads were characterized by NMR, infrared, DLS, TEM, X-ray diffraction. The replacement of CH3COOH by SiO2@COOH (100 times less on molar ratio) has been evaluated for (ep)oxi-dation on several substrates (cyclooctene, cyclohexene, cyclohexanol) and discussed in terms of activity and green metrics.

Different loadings of Cu single atoms were anchored on a graphitic carbon nitride (g-C3N4) matrix using a two-step thermal synthesis method and applied in liquid-phase cyclohexene oxidation under mild conditions using molecular O2 as the oxidizing agent. The oxidation state of Cu was determined to be Cu+, which is in linear coordination with two neighboring nitrogen atoms at a distance of 1.9 ?. The catalyst with 0.9 wt % Cu pyrolyzed at 380 °C was found to exhibit the best catalytic performance with the highest conversion up to 82% with an allylic selectivity of 55%. It also showed high reusability over four catalytic runs without any detectable Cu leaching. Cyclohexene oxidation followed first-order kinetics with an apparent activation energy of 66.2 kJ mol-1. The addition of hydroquinone as a radical scavenger confirmed that cyclohexene oxidation proceeds via a radical mechanism. Time-resolved in situ attenuated total reflection infrared (ATR-IR) spectroscopy was carried out to qualitatively monitor the cyclohexene oxidation pathways. The comparison with the homogeneous analogue Cu(I) iodide indirectly verified the linearly N-coordinated single Cu(I) species to be the active sites for cyclohexene oxidation.

Nickel phosphide, Ni2P, nanoparticles supported on SiO2 show a marked volcano shaped size dependence on hydrogenation of phenol. Kinetic analysis and physicochemical characterization shows the electron density of Ni to increase with increasing Ni2P size, enhancing in turn the H2 adsorption strength. For particles below 15 nm, H adsorbs weakly causing a low surface coverage of H, gradually increasing with particle size. For large particles, hydrogen binds too strongly causing a high coverage but low catalytic activity. The remarkable size dependence of the electronic properties show that Ni2P particle size can be used to fine-tune its activity for hydrogenation.

Zr-monosubstituted Lindqvist-type polyoxometalates (Zr-POMs), (Bu4N)2[W5O18Zr(H2O)3] (1) and (Bu4N)6[{W5O18Zr(μ-OH)}2] (2), have been employed as molecular models to unravel the mechanism of hydrogen peroxide activation over Zr(IV) sites. Compounds 1 and 2 are hydrolytically stable and catalyze the epoxidation of C?C bonds in unfunctionalized alkenes and α,β-unsaturated ketones, as well as sulfoxidation of thioethers. Monomer 1 is more active than dimer 2. Acid additives greatly accelerate the oxygenation reactions and increase oxidant utilization efficiency up to >99%. Product distributions are indicative of a heterolytic oxygen transfer mechanism that involves electrophilic oxidizing species formed upon the interaction of Zr-POM and H2O2. The interaction of 1 and 2 with H2O2 and the resulting peroxo derivatives have been investigated by UV-vis, FTIR, Raman spectroscopy, HR-ESI-MS, and combined HPLC-ICP-atomic emission spectroscopy techniques. The interaction between an 17O-enriched dimer, (Bu4N)6[{W5O18Zr(μ-OCH3)}2] (2′), and H2O2 was also analyzed by 17O NMR spectroscopy. Combining these experimental studies with DFT calculations suggested the existence of dimeric peroxo species [(μ-?2:?2-O2){ZrW5O18}2]6- as well as monomeric Zr-hydroperoxo [W5O18Zr(?2-OOH)]3- and Zr-peroxo [HW5O18Zr(?2-O2)]3- species. Reactivity studies revealed that the dimeric peroxo is inert toward alkenes but is able to transfer oxygen atoms to thioethers, while the monomeric peroxo intermediate is capable of epoxidizing C?C bonds. DFT analysis of the reaction mechanism identifies the monomeric Zr-hydroperoxo intermediate as the real epoxidizing species and the corresponding α-oxygen transfer to the substrate as the rate-determining step. The calculations also showed that protonation of Zr-POM significantly reduces the free-energy barrier of the key oxygen-transfer step because of the greater electrophilicity of the catalyst and that dimeric species hampers the approach of alkene substrates due to steric repulsions reducing its reactivity. The improved performance of the Zr(IV) catalyst relative to Ti(IV) and Nb(V) catalysts is respectively due to a flexible coordination environment and a low tendency to form energy deep-well and low-reactive Zr-peroxo intermediates.

La1?xSrxCoO3 (x=0, 0.1, 0.2, 0.3, 0.4) nanoparticles were prepared by spray-flame synthesis and applied in the liquid-phase oxidation of cyclohexene with molecular O2 as oxidant under mild conditions. The catalysts were systematically characterized by state-of-the-art techniques. With increasing Sr content, the concentration of surface oxygen vacancy defects increases, which is beneficial for cyclohexene oxidation, but the surface concentration of less active Co2+ was also increased. However, Co2+ cations have a superior activity towards peroxide decomposition, which also plays an important role in cyclohexene oxidation. A Sr doping of 20 at. % was found to be the optimum in terms of activity and product selectivity. The catalyst also showed excellent reusability over three catalytic runs; this can be attributed to its highly stable particle size and morphology. Kinetic investigations revealed first-order reaction kinetics for temperatures between 60 and 100 °C and an apparent activation energy of 68 kJ mol?1 for cyclohexene oxidation. Moreover, the reaction was not affected by the applied O2 pressure in the range from 10 to 20 bar. In situ attenuated total reflection infrared spectroscopy was used to monitor the conversion of cyclohexene and the formation of reaction products including the key intermediate cyclohex-2-ene-1-hydroperoxide; spin trap electron paramagnetic resonance spectroscopy provided strong evidence for a radical reaction pathway by identifying the cyclohexenyl alkoxyl radical.

The catalytic performance of Zr-abtc and MIP-200 metal–organic frameworks consisting of 8-connected Zr6 clusters and tetratopic linkers was investigated in H2O2-based selective oxidations and compared with that of 12-coordinated UiO-66 and UiO-67. Zr-abtc demonstrated advantages in both substrate conversion and product selectivity for epoxidation of electron-deficient C=C bonds in α,β-unsaturated ketones. The significant predominance of 1,2-epoxide in carvone epoxidation, coupled with high sulfone selectivity in thioether oxidation, points to a nucleophilic oxidation mechanism over Zr-abtc. The superior catalytic performance in the epoxidation of unsaturated ketones correlates with a larger amount of weak basic sites in Zr-abtc. Electrophilic activation of H2O2 can also be realized, as evidenced by the high activity of Zr-abtc in epoxidation of the electron-rich C=C bond in caryophyllene. XRD and FTIR studies confirmed the retention of the Zr-abtc structure after the catalysis. The low activity of MIP-200 in H2O2-based oxidations is most likely related to its specific hydrophilicity, which disfavors adsorption of organic substrates and H2O2.

Based on the two anomeric methyl 3-amino-2,3-dideoxy-D-arabino-hexopyranosides ten new sugar-modified Schiff base ligands have been synthesized after monocondensation reaction with five o-hydroxyaromatic aldehydes, i.e. salicylaldehyde and its five para-s

Desulfurization of a variety of thiiranes to alkenes occurs chemoselectively in high yields upon treatment with MoCl5/Zn system under mild conditions. The new methodology demonstrates high functional group tolerance toward chloro, bromo, fluoro, methoxy, ester, ether and keto groups.

The invention discloses a preparation process of 1, 3-cyclohexane dimethylamine, and the process comprises the following steps: 1) isomerization dehydrogenation of cyclohexene oxide: converting cyclohexene oxide into cyclohexenone under the action of an isomerization dehydrogenation catalyst; 2) addition of cyclohexenone and hydrocyanic acid: reacting cyclohexenone under the action of hydrocyanicacid and an alkaline addition catalyst to generate 1, 3-dicyano-1-cyclohexanol; 3) dehydration and hydrogenation of 1, 3-dicyano-1-cyclohexanol: carrying out dehydration and hydrogenation on the obtained 1, 3-dicyano-1-cyclohexanol in the presence of hydrogen and a hydrogenation catalyst to generate 1, 3-cyclohexanediamine. Compared with the prior art, the invention has the beneficial effects thatthe raw materials are cheap and easy to obtain; the reaction yield is high, and the total yield is greater than or equal to 90%; the reaction conditions are mild and suitable for industrialization.

Catalytic oxidation reaction using green oxidants plays an important role in modern chemical engineering; however, thein situgenerated active species and the related catalytic mechanism need to be understood in depth. For this purpose, Cr-substituted aluminoborate Cr-PKU-8 catalysts were synthesized and applied as recyclable heterogeneous catalysts for the oxidation of aliphatic and aromatic alcohols usingtert-butylhydroperoxide (TBHP). Both high efficiency and selectivity (>99%) were achieved during the dehydrogenation of varioussec-alcohols into acetone in H2O solvent medium. From the analyses using isotopic tracer, molecular probe and cyclic voltammetry strategies, the chromium ions were observed to undergo a Cr3+-Cr2+-Cr3+redox cycle. DFT calculations suggest thatt-BuOO* is more energetically favourable for hydrogen abstraction fromsec-alcohol thant-BuO*, and probably acts as the key active species. Accordingly, the reaction scheme was proposed to interpret the catalytic process based on the observed results.

g-C3N4/metal halide perovskite composites were prepared and used for the first time as photocatalysts forin situ1O2generation to perform hetero Diels-Alder, ene and oxidation reactions with suitable dienes and alkenes. The standardized methodology was made applicable to a variety of olefinic substrates. The scope of the method is finely illustrated and the reactions afforded desymmetrized hydroxy-ketone derivatives, unsaturated ketones and epoxides. Some limitations were also observed, especially in the case of the alkene oxidations, and poor chemoselectivity was somewhere observed in this work which is the first application of MHP-based composites forin situ1O2generation. The experimental protocol can be used as a platform to further expand the knowledge and applicability of MHPs to organic reactions, since perovskites offer a rich variety of tuning strategies which may be explored to improve reaction yields and selectivities.

Iodosylbenzene (PhIO) and its derivatives have attracted significant attention due to their various applications in organic synthesis and biomimetic studies. For example, PhIO has been extensively used for generating high-valent metal-oxo species that have been regarded as key intermediates in diverse oxidative reactions in biological system. However, recent studies have shown that metal-iodosylbenzene adduct, known as a precursor of metal-oxo species, plays an important role in transition metal-catalyzed oxidation reactions. During last few decades, extensive investigations have been conducted on the synthesis and reactivity studies of metal-iodosylbenzene adducts with early and middle transition metals including manganese, iron, cobalt. Nevertheless, metal-iodosylbenzene adducts with late transition metals such as nickel, copper and zinc, still remains elusive. Herein, we report a novel copper(II)-iodosylbenzene adduct bearing a linear ligand composed of two pyridine rings and an ethoxyethanol side-chain, [Cu(OIPh)(HN3O2)]2+ (1). The copper(II)-iodosylbenzene adduct was characterized by several spectroscopic methods including UV–vis spectroscopy, electrospray ionization mass spectrometer (ESI MS), and electron paramagnetic resonance (EPR) combined with theoretical calculations. Interestingly, 1 can carry out the catalytic sulfoxidation reaction. In sulfoxidation reaction with thioanisole under catalytic reaction condition, not only two-electron but also four-electron oxidized products such sulfoxide and sulfone were yielded, respectively. However, 1 was not an efficient oxidant towards C–H bond activation and epoxidation reactions due to the steric hindrance created by the intramolecular H-bonding interaction between HN3O2 ligand and iodosylbenzene moiety.

Abstract: The selective hydrogenation of α,β-unsaturated aldehydes plays a crucial role in industrial production, and an efficient non-noble metal catalyst for it has been pursued to reduce the cost. Herein, we report an amorphous nickel phosphide for the selective hydrogenation of cinnamaldehyde. Compared to crystalline nickel phosphide, amorphous nickel phosphide showed both high activity and high selectivity to target products. Its catalytic performance was also better than that of commercial Pd/C catalyst. In addition, initial P/Ni ratio was found to be an important factor to affect the activity of amorphous nickel phosphide. High initial P/Ni ratio led to high activity owing to small particles, high surface area and strong metallicity of as-synthesized catalyst. Moreover, excellent catalytic performances of amorphous nickel phosphide were observed in the selective hydrogenation of different α,β-unsaturated aldehydes and ketones. Graphic Abstract: [Figure not available: see fulltext.].

Direct selective desaturation of carbonyl compounds to synthesize α,β-unsaturated carbonyl compounds represents an environmentally benign alternative to classical stepwise procedures. In this study, we designed an ideal CeO2-supported Pd(II)-on-Au nanoparticle catalyst (Pd/Au/CeO2) and successfully achieved heterogeneously catalyzed selective desaturation of cyclohexanones to cyclohexenones using O2 in air as the oxidant. Besides cyclohexenones, various bioactive enones can also be synthesized from the corresponding saturated ketones under open air conditions in the presence of Pd/Au/CeO2. Preliminary mechanistic studies revealed that α-C-H bond cleavage in the substrates is the turnover-limiting step of this desaturation reaction.

A novel K2S2O8-promoted C-Se bond formation from cross-coupling under neutral conditions has been developed. A variety of aldehydes and ketones react well using K2S2O8 as the oxidant in the absence of catalyst and afford desired products in moderate to excellent yields. This protocol provides a very simple route for the synthesis of α-phenylseleno carbonyl compounds and α,β-unsaturated carbonyl compounds.

Mo(CO)6 converts a broad range of thiiranes to the corresponding alkenes in high yields under neutral conditions. It has been found that this protocol is chemoselective and tolerates a variety of functional groups such as chloro, bromo, fluoro, ester, methoxy, ether and keto.

The present invention relates to a preparation method of 2-cyclohexene-1-one, which comprises: 1, carrying out an oxidation reaction on cyclohexene, an oxidizing agent, an accelerator, an alkali and asolvent under mild conditions, wherein the accelerator

β-Chlorination of meso-tetraphenylporphyrin, H2TPP leads to the formation of H2TPPClx (X = 2, 4, 6 and 8) with absorption bands in the range of 421–451 and 650–715 nm, for the Soret and Q(0,0) bands, respectively. H2

A metal-organic framework, MIL-47(V) containing coordinatively saturated V+IV sites linked together by terephthalic linkers, was prepared by a solvothermal method and evaluated as a catalyst in the epoxidation of cyclohexene. We have compared the catalytic activity in the condensed and gas phase oxidation of cyclohexene to discuss the effect of temperature and reaction phase in cyclohexene epoxidation over MIL-47(V). The catalysts were examined for the epoxidation of cyclohexene with H2O2 at 50, 65, 120, and 150 °C. We observed significant differences in product selectivity between liquid-phase and gas-phase operations and confirmed that the active sites are tightly incorporated into the MOF as node channels and thus resistant to leaching.

New chiral mononuclear cis-dioxidomolybdenum(VI) complexes, [MoO2(HL1-9)] and [MoO2(HL10)(CH3OH)], have been synthesized by the reaction of MoO2(acac)2 with tetradentate Schiff bases derived from various substituted salicylaldehydes and R(+)-3-amino-1,2-propanediol. All complexes have been characterized by elemental analysis, circular dichroism, electronic, IR and NMR (1H, 13C) spectroscopy. The molecular and crystal structure of [MoO2(HL10)(CH3OH)] elucidated by single-crystal X-ray diffraction revealed a six-coordinate distorted octahedral geometry and coordination of methanol molecule leaving one hydroxyl group uncoordinated. Surprisingly, NMR measurements made for [MoO2(HL1-9)] undoubtedly show that Schiff bases behave as dibasic tetradentate ONOO donor ligands and no solvent coordination has been observed. The catalytic activity studies have been also performed for all complexes in asymmetric sulfoxidation of thioanisole and epoxidation of styrene, cyclohexene and two monoterpenes, i.e. S(?)-limonene and (?)-α-pinene, using aqueous 30% H2O2 or tert-butyl hydroperoxide (TBHP) as the oxygen source.

Nanosized gold entities immobilized on short-channel SBA-15 mesoporous materials functionalized solely with mercaptopropyl groups and together with propyl and octyl moieties have been prepared following a two-steps procedure. These materials have been used as catalysts for the oxidation of cyclohexene with molecular oxygen in liquid phase at atmospheric pressure. First, SBA-15 materials functionalized only with mercaptopropyl groups and with a combination of these groups with two hydrophobic moieties, namely propyl and octyl, have been synthesized in the presence of the non-ionic surfactant P104. Small particles having short channel length have been identified by TEM and SEM. In order to study the influence of the nature of the sulphur functional group, these S-bearing materials were also oxidized with hydrogen peroxide or dimethyldioxirane (DMD) to sulfonic groups prior to gold immobilization. The effectiveness of these oxidation methods was assessed by 29Si MAS NMR, 13C CP MAS NMR, XPS, chemical and thermal analysis, and it has been found that DMD oxidized efficiently thiol groups to sulfonic groups, but H2O2 leaves a fraction of unreacted thiol. In a second step, nanosized gold entities have been prepared by a two-liquid phases route involving rosemary oil as organic phase and an aqueous phase formed by dissolving gold in a solution of ammonium chloride in concentrated nitric acid (aqua regia). Following this method, a fraction of the Au dissolved in the aqua regia solution is spontaneously reduced and transferred to the essential oil phase. Upon contacting the gold-bearing organic layer with the mesoporous materials, gold is actually immobilized on them, rendering metal contents in the range 1.1-0.2 wt.percent, being those functionalized with alkyl chains the least efficient in capturing gold from the organic phase. No surface plasmon resonance band at 520 nm characteristic of gold nanoparticles has been detected by UV–vis spectroscopy in these Au-containing materials. All of them are active and selective for the allylic oxidation of cyclohexene, but their specific activity varies as a function of the nature of the functional groups. It has been found that the most active catalysts are those pre-oxidized with DMD. The presence of hydrophobic octyl groups increases substantially the turnover number of the reaction (TON), while the short-chain propyl moieties hardly affect the activity. It has been found that the nanosized gold entities initially present in the catalysts evolve in the reaction medium towards the formation of nanoparticles.

A dimeric copper(II) complex, bis{(2-[1-(aminoethylimino)ethyl]-phenoxo}-di-μ1,1-azido-dicopper(II), [Cu2(L)2(μ2-1,1-N3)2] (1) [L = 2-[1-(aminoethylimino)ethyl]-phenoxo ion], has been isolated using a self-assembly reaction using a 1:1:1 molar ratio of Cu(NO3)2·3H2O, HL and NaN3 in methanol at room temperature and characterized through X-ray diffraction analysis and spectroscopic studies. X-ray structural analysis reveals that 1 consists of two distinct dinuclear molecular units, where each copper(II) center in the individual dinuclear unit adopts a distorted square pyramidal geometry with a CuN4O chromophore ligated through a tridentate (NNO) Schiff base and two N atoms of two different bridging azides in μ1,1-mode. Two Cu(II) centers are linked through double μ2-1,1-N3 bridges to form the dinuclear unit [Cu2(L)2(μ2-1,1-N3)2]. In the crystalline state, the dinuclear units in 1 are associated through weak intermolecular N-H?O hydrogen bonds to afford a 2-D sheet structure viewed along the crystallographic a-axis. The small magnitude of the antiferromagnetic interaction (J = –0.45 cm?1) is a result of the long Cu···Cu separation (3.205(2) ?). The catalytic efficacy of 1 was studied in a series of solvents for the epoxidation of alkenes using tert-butyl-hydroperoxide (TBHP) as an efficient oxidant under mild conditions.

With the assistance of hydrogen bonds of the o-amino group, we have successfully tuned a coordination structure from a metal–organic polyhedron (MOP) to a two-dimensional (2D) metal–organic framework (MOF). The amino group forms hydrogen bonds with the two vicinal carboxylic groups, and induces the ligand to coordinate with copper ions to form the 2D structure. The obtained 2D Cu-based MOF (Cu-AIA) has been applied as an efficient heterogeneous catalyst in the aerobic epoxidation of olefins by using air as oxygen source. Without the aggregation problem of active sites in MOPs, Cu-AIA possesses much higher reactivity than MOP-1. Furthermore, the amino group of the framework has been used as a modifiable site through post-synthetic metalation (PSMet) to prepare a 2D MOF-supported Pd single-site heterogeneous catalyst, which shows excellent catalytic performance for the Suzuki reaction. It indicates that Cu-AIA can also work as a good 2D MOF carrier for the derivation of other heterogeneous catalysts.

The confinement of cerium oxide (CeO2) nanoparticles within hollow carbon nanostructures has been achieved and harnessed to control the oxidation of cyclohexene. Graphitized carbon nanofibers (GNF) have been used as the nanoscale tubular host and filled by sublimation of the Ce(tmhd)4 complex (where tmhd = tetrakis(2,2,6,6-Tetramethyl-3,5-heptanedionato)) into the internal cavity, followed by a subsequent thermal decomposition to yield the hybrid nanostructure CeO2?GNF, where nanoparticles are preferentially immobilized at the internal graphitic step-edges of the GNF. Control over the size of the CeO2 nanoparticles has been demonstrated within the range of about 4-9 nm by varying the mass ratio of the Ce(tmhd)4 precursor to GNF during the synthesis. CeO2?GNF was effective in promoting the allylic oxidation of cyclohexene in high yield with time-dependent control of product selectivity at a comparatively low loading of CeO2 of 0.13 mol %. Unlike many of the reports to date where ceria catalyzes such organic transformations, we found the encapsulated CeO2 to play the key role of radical initiator due to the presence of Ce3+ included in the structure, with the nanotube acting as both a host, preserving the high performance of the CeO2 nanoparticles anchored at the GNF step-edges over multiple uses, and an electron reservoir, maintaining the balance of Ce3+ and Ce4+ centers. Spatial confinement effects ensure excellent stability and recyclability of CeO2?GNF nanoreactors.

The science of particles on a sub-nanometer (ca. 1 nm) scale has attracted worldwide attention. However, it has remained unexplored because of the technical difficulty in the precise synthesis of sub-nanoparticles (SNPs). We recently developed the “atom-hybridization method (AHM)” for the precise synthesis of SNPs by using a suitably designed macromolecule as a template. We have now investigated the chemical reactivity of alloy SNPs obtained by the AHM. Focusing on the coinage metal elements, we systematically evaluated the oxidation reaction of an olefin catalyzed by these SNPs. The SNPs showed high catalytic performance even under milder conditions than those used with conventional catalysts. Additionally, the hybridization of multiple elements enhanced the turnover frequency and the selectivity for the formation of the hydroperoxide derivative. We discuss the unique quantum-sized catalysts providing generally unstable hydroperoxides from the viewpoint of the miniaturization and hybridization of materials.

Three new iron(II)-benzilate complexes [(N4Py)FeII(benzilate)]ClO4 (1), [(N4PyMe2)FeII(benzilate)]ClO4 (2) and [(N4PyMe4)FeII(benzilate)]ClO4 (3) of neutral pentadentate nitrogen donor ligands have been isolated and characterized to study their dioxygen reactivity. Single-crystal X-ray structures reveal a mononuclear six-coordinate iron(II) center in each case, where benzilate binds to the iron center in monodentate mode via one carboxylate oxygen. Introduction of methyl groups in the 6-positions of the pyridine rings makes the N4PyMe2 and N4PyMe4 ligand fields weaker compared to that of the parent N4Py ligand. All the complexes (1–3) react with dioxygen to decarboxylate the coordinated benzilate to benzophenone quantitatively. The decarboxylation is faster for the complex of the more sterically hindered ligand and follows the order 3>2>1. The complexes display oxygen atom transfer reactivity to thioanisole and also exhibit hydrogen atom transfer reactions with substrates containing weak C?H bonds. Based on interception studies with external substrates, labelling experiments and Hammett analysis, a nucleophilic iron(II)-hydroperoxo species is proposed to form upon two-electron reductive activation of dioxygen by each iron(II)-benzilate complex. The nucleophilic oxidants are converted to the corresponding electrophilic iron(IV)-oxo oxidant upon treatment with a protic acid. The high-spin iron(II)-benzilate complex with the weakest ligand field results in the formation of a more reactive iron-oxygen oxidant.

A novel type of hybrid catalytic materials [MnII-L?BC] has been developed using biochar (BC) as support material for covalent grafting of a MnII Schiff-base catalyst (MnII-L). The hybrid [MnII-L?BC] materials have been evaluated for an important catalytic process, epoxidation of olefins using H2O2 as oxidant. A number of different substrates were used, with cyclohexene achieving the highest yields. When compared to the non-grafted, homogeneous MnII-L, the hybrid catalysts [MnII-L?BC] show a significant enhancement of the catalytic efficiency i.e. as documented by the increase of Turnover Numbers (TONs) (826 for [MnII-L-SS550ox] and 822 for [MnII-L-SW550ox]) and Turnover Frequencies (TOFs) (551 h?1 for [MnII-L-SS550ox] and 411 h?1 for [MnII-L-SW550ox]). The interfacial catalytic mechanism and the role of the BC support have been analyzed by Raman and Electron Paramagnetic Resonance spectroscopies. Based on these data we discuss a mechanism where the high efficiency of the hybrid materials involves the biochar carbon layers acting as promoters of the substrate and products kinetics. To a broader context, this work exemplifies that biochar-based hybrid materials are potent for oxidative catalysis technologies.

A selective, practical, and scalable aerobic oxidation of alcohols is described that uses catalytic amounts of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and HNO3, with molecular oxygen serving as the terminal oxidant. The method was successfully applied to the oxidation of a wide range of benzylic, propargylic, and allylic alcohols, including two natural products, namely, carveol and podophyllotoxin. The conditions are also applicable to the selective oxidative deprotection of p-methoxybenzyl ethers.

The combination of [Cu(MeCN)4]TFA·TFAH (TFA = O2CCF3) with Feringa's phosphoramidite ligand (LA) provides an exceptionally active (0.75 mol %) catalyst for asymmetric conjugate additions of ZnR2 (R = Et and Me at -40 to -80 °C) to enones. Kinetic and other studies of the addition of ZnEt2 to cyclohex-2-en-1-one indicate a transition state stoichiometry composition of (ZnEt2)3(enone)4Cu2(LA)3 that is generated by transmetalation from Et2Zn(enone)2. Catalyst genesis is significantly slower than turnover (which has limited previous attempts to attain useful kinetic data); in the initial stages, varying populations of catalytically inactive, off-cycle, species are present. These issues are overcome by a double-dose kinetic analysis protocol. A rest state of [LACu(Et)(μ-TFA)(μ-{(enone)(ZnEt)2(enolate)})CuLA2]+ (through the equivalence of enolate = enone + ZnEt2) is supported by DFT studies (ωB97X-D/SRSC). Rate-determining ZnEt2(enone)2 transmetalation drives the exceptionally high catalytic activity of this system.

The elimination of waste and by-product generation and reduced dependence on hazardous chemicals are the key steps towards environmentally sustainable chemical transformations. Heterogeneously catalysed oxidation of cyclohexene with environmentally friendly oxidizing agents such as O2, H2O2 and tert-butyl hydroperoxide (TBHP) has great potential to replace existing processes using stoichiometric oxidants. A series of spray-flame synthesised nanoparticulate LaCo1-xFexO3 catalysts was employed for cyclohexene oxidation, and the comparative results showed that TBHP led to the highest initial activity and allylic selectivity, but O2 resulted in higher conversion for longer reaction times. Furthermore, the influence of Fe substitution was studied, which did not show any beneficial synergistic effects. LaCoO3 was found to be the optimum catalyst for cyclohexene oxidation with O2, following first-order reaction kinetics with an apparent activation energy of 57 kJ mol-1. The catalyst showed good reusability due to its highly stable particle size, morphology and perovskite structure. 7-Oxabicyclo[4.1.0]heptan-2-one was identified to be formed by the oxidation of 2-cyclohexene-1-one with 2-cyclohexene-1-hydroperoxide.

Catalytic oxidation of hydrocarbons with hydrogen peroxide (H2O2) has been of the utmost importance for several decades. The vast majority of studies have been performed in the condensed phase, even though condensed phases introduce complex solvent effects and can promote the leaching of active sites. In response, we have built a custom reactor system to understand H2O2 activation and selective oxidation in the vapor-phase. In this report, we study the epoxidation of cyclohexene with H2O2 over four Lewis-acidic metal oxide catalysts: Ti and Nb grafted on SiO2 and on the Zr based metal-organic framework, NU-1000. The M-SiO2 materials are highly selective to the formation of epoxides and diols, as they can be in the condensed phase, while the NU-1000 based materials are far more prone to overoxidation to CO2, which appears to be connected to their strong reactant adsorption. Apparent activation energies are calculated for all materials when operating in the same kinetic regime, and the heats of cyclohexene adsorption into their pores are then used to directly compare intrinsic enthalpies of activation in the vapor vs condensed phase for the M-SiO2 catalysts. Nb-SiO2 catalysts exhibit similar intrinsic enthalpies of activation in the vapor and condensed phases, whereas the condensed phase transition state in Ti-SiO2 is 24 kJ/mol lower in energy than that of the same material in the vapor phase. These experiments establish another methodology for understanding the various roles of solvent in selective oxidation reactions and studying these reactions under conditions that differ significantly from the thousands of prior studies in the condensed phase.

Metal-organic frameworks (MOFs) are newly emerging and versatile platforms for designing catalysts, and catalytic oxidation of cyclohexene has attracted much academic and industrial attention for the versatile reactivity of the substrate and the great importance of the various oxygenated products. Here we report the bifunctional catalytic properties of a sulfonic-containing MOF, MIL-101-SO3H, for cyclohexene oxidation. The sulfonic group and the Cr(III) site acts in a complementary or collaborative way. The Cr(III) framework promotes the oxidation to 3-hydroperoxycyclohex-1-ene (perox) and 2-cyclohexen-1-one (1-one) (route A), whereas the sulfonic group in collaboration with the Cr(III) framework promotes the oxidation to diol (route B) and also enhances further conversions in route A: from perox to 1-one, to 2-cyclohexen-1,4-dione (dione) and even to benzoquinone. With the bifunctional MOF, molecular oxygen alone cannot oxidize cyclohexene but participates as oxidant cooperating with tert-butyl hydroperoxide (TBHP) to accelerate the reactions and to alter the product distribution in favor of dione.

Gold nanoclusters (d p = 6.3 nm, 3.5 wt% S) was contacted with aliquots of the Au-containing essential oil phase taken at 1, 3, 6 and 8 days of contact time between both phases. In this way, gold was immobilized on the support, ranging from 0.4 wt% for the 1-day sample, to 2.7 wt% in the 3-days material. UV–vis spectra show the presence of gold nanoclusters in these samples, but the surface plasmon resonance at 520 cm?1, characteristic of Au nanoparticles, was not detected save for the 3-days sample. 13C MAS NMR and TG evidence that the thiol groups of the support remain mostly unaltered for the 1-day sample, but oxidation to sulfonic acid groups becomes apparent for contact time > 3 days, and reaches nearly 60 % of the total sulphur species after 8 days of contact time as estimated from XPS analysis. The Au-SH-bearing catalyst is inactive for cyclohexene oxidation with molecular oxygen in liquid phase, but those having sulfonic groups are active and selective for its allylic oxidation. It has been found for the 8-day catalyst that the gold nanoclusters partially evolve spontaneously in the reaction medium to form gold nanoparticles, and this agglomeration process parallels the increase in catalyst activity.