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Biomimetic alkane oxidation by iodosylbenzene and iodobenzene diacetate catalyzed by a new manganese porphyrin: Water effect
This work describes the synthesis and characterization of the novel third-generation catalyst 5,10-(3,5-bromo,4-aminophenyl)-15,20-(phenyl)-2,3,7,8,12,13,17,18-octabromoporphyrinatomanganese(III) chloride, cis-[MnIIIBr12DAPDPP]Cl, and compares the catalytic activity of this compound with the catalytic activity of the first- and second-generation manganese porphyrins [MnIIITPP]Cl and cis-[MnIIIDAPDPP]Cl, respectively, in cyclohexane, adamantane and n-hexane, oxidation by iodosylbenzene (PhIO) or iodobenzene diacetate (PhI(OAc)2). This work also investigates how addition of water and imidazole influences the catalytic systems in the adamantane and cyclohexane oxidation. In the absence of water and imidazole, cis-[MnIIIBr12DAPDPP]Cl leads to higher product yields as compared with [MnIIITPP]Cl and cis-[MnIIIDAPDPP]Cl in cyclohexane oxidation. The third-generation (β-octabrominated) cis-[MnIIIBr12DAPDPP]Cl was not fully destroyed in reactions with PhI(OAc)2 as oxidant. In the presence of imidazole, [MnIIITPP]Cl and cis-[MnIIIDAPDPP]Cl give superior cyclohexanol yields as compared with cis-[MnIIIBr12DAPDPP]Cl. Addition of water during adamantane oxidation by PhI(OAc)2 increases 1-adamantanol yield. As for cyclohexane oxidation by PhIO or PhI(OAc)2, the presence of water raises product yields and diminishes catalyst destruction, especially in the case of cis-[MnIIIDAPDPP]Cl. The presence of water in systems employing PhI(OAc)2 as oxidant affords higher product yields as compared with systems that use PhIO as oxidant.
Da Silva, Vinícius Santos,Idemori, Ynara Marina,DeFreitas-Silva, Gilson
p. 54 - 62
(2015)
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2,2′-Bipyridine-α,α′-trifluoromethyl-diol ligand: Synthesis and application in the asymmetric Et2Zn alkylation of aldehydes
A chiral 2,2′-bipyridine ligand (1) bearing α,α′-trifluoromethyl-alcohols at 6,6′-positions was designed in five steps affording either the R,R or S,S enantiomer with excellent stereoselectivities, i.e. 97% de, >99% ee and >99.5% de, >99.5% ee, respectively. The key step for reaching high levels of stereoselectivity was demonstrated to be the resolution of the α-CF3-alcohol using (S)-ibuprofen as the resolving agent. An initial application for the 2,2′-bipyridine-α,α′-CF3-diol ligand was highlighted in the ZnII-catalyzed asymmetric ethylation reaction of aromatic, heteroaromatic, and aliphatic aldehydes. Synergistic electron deficiency and steric hindrance properties of the newly developed ligand afforded the corresponding alcohols in good to excellent yields (up to 99%) and enantioselectivities (up to 95% ee). As observed from single crystal diffraction analysis, the complexation of the 2,2′-bipyridine-α,α′-CF3-diol ligand generates an unusual hexacoordinated ZnII.
Lauzon, Samuel,Ollevier, Thierry
supporting information
p. 11025 - 11028
(2021/11/03)

Hydrodeoxygenation of C4-C6 sugar alcohols to diols or mono-alcohols with the retention of the carbon chain over a silica-supported tungsten oxide-modified platinum catalyst
The hydrodeoxygenation of erythritol, xylitol, and sorbitol was investigated over a Pt-WOx/SiO2 (4 wt% Pt, W/Pt = 0.25, molar ratio) catalyst. 1,4-Butanediol can be selectively produced with 51% yield (carbon based) by erythritol hydrodeoxygenation at 413 K, based on the selectivity over this catalyst toward the regioselective removal of the C-O bond in the -O-C-CH2OH structure. Because the catalyst is also active in the hydrodeoxygenation of other polyols to some extent but much less active in that of mono-alcohols, at higher temperature (453 K), mono-alcohols can be produced from sugar alcohols. A good total yield (59%) of pentanols can be obtained from xylitol, which is mainly converted to C2 + C3 products in the literature hydrogenolysis systems. It can be applied to the hydrodeoxygenation of other sugar alcohols to mono-alcohols with high yields as well, such as erythritol to butanols (74%) and sorbitol to hexanols (59%) with very small amounts of C-C bond cleavage products. The active site is suggested to be the Pt-WOx interfacial site, which is supported by the reaction and characterization results (TEM and XAFS). WOx/SiO2 selectively catalyzed the dehydration of xylitol to 1,4-anhydroxylitol, whereas Pt-WOx/SiO2 promoted the transformation of xylitol to pentanols with 1,3,5-pentanetriol as the main intermediate. Pre-calcination of the reused catalyst at 573 K is important to prevent coke formation and to improve the reusability.
Betchaku, Mii,Cao, Ji,Liu, Lujie,Nakagawa, Yoshinao,Tamura, Masazumi,Tomishige, Keiichi,Yabushita, Mizuho
supporting information
p. 5665 - 5679
(2021/08/16)

Chemoselective and Site-Selective Reductions Catalyzed by a Supramolecular Host and a Pyridine-Borane Cofactor
Supramolecular catalysts emulate the mechanism of enzymes to achieve large rate accelerations and precise selectivity under mild and aqueous conditions. While significant strides have been made in the supramolecular host-promoted synthesis of small molecules, applications of this reactivity to chemoselective and site-selective modification of complex biomolecules remain virtually unexplored. We report here a supramolecular system where coencapsulation of pyridine-borane with a variety of molecules including enones, ketones, aldehydes, oximes, hydrazones, and imines effects efficient reductions under basic aqueous conditions. Upon subjecting unprotected lysine to the host-mediated reductive amination conditions, we observed excellent ?-selectivity, indicating that differential guest binding within the same molecule is possible without sacrificing reactivity. Inspired by the post-translational modification of complex biomolecules by enzymatic systems, we then applied this supramolecular reaction to the site-selective labeling of a single lysine residue in an 11-amino acid peptide chain and human insulin.
Morimoto, Mariko,Cao, Wendy,Bergman, Robert G.,Raymond, Kenneth N.,Toste, F. Dean
supporting information
p. 2108 - 2114
(2021/02/06)

Chromium-Catalyzed Production of Diols From Olefins
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.
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(2021/03/19)

Synthesis of TS-1 zeolites from a polymer containing titanium and silicon
The synthesis of TS-1 zeolites is regarded as a milestone in zeolite history, and it has led to the revolution of the green oxidation system of using H2O2as an oxidant, leaving only water as the byproduct. However, because of the highly hydrolyzable titanium source, the preparation of TS-1 requires complex synthesis conditions. Moreover, the difference in the hydrolysis rate between the silicon source and titanium source tends to increase the difficulty of titanium insertion into the framework, and it is easy to generate extra-framework Ti species during the synthesis. Here, a high-quality TS-1 zeolite with a large external surface area and free of extra-framework Ti species has been successfully synthesized by using a kind of novel polymer containing titanium and silicon. Due to the high hydrolysis resistance of the polymer reagent, a good matching of the hydrolysis rate between the silicon source and the titanium source is realized during crystallization, which facilitates the incorporation of titanium into the framework. Furthermore, the TS-1 zeolite exhibited excellent catalytic performance inn-hexane oxidation with hydrogen peroxide as the oxidant. This method of synthesizing zeolites from polymers is expected to be widely applied for the synthesis of other titanium-containing zeotype materials.
Xing, Jiacheng,Yuan, Danhua,Liu, Hanbang,Tong, Yansi,Xu, Yunpeng,Liu, Zhongmin
p. 6205 - 6213
(2021/03/22)

Catalytic oxidation of primary c-h bonds in alkanes with bioinspired catalysts
Catalytic oxidation of primary C-H bonds of alkanes with a series of iron and manganese catalysts is investigated. Products resulting from oxidation of methylenic sites are observed when hexane (S1) is used as model substrate, while corresponding primary C-H bonds remain unreactive. However, by using 2,2,3,3-tetra-methylbutane (S2) as model substrate, which only contains primary alkyl C-H bonds, oxidation takes place catalytically using a combination of hydrogen peroxide, a manganese catalyst and acetic acid as co-catalyst, albeit with modest yields (up to 4.4 TON). Complexes bearing tetradentate aminopyridine ligands provide the best yields, while a related pentadentate ligand provides smaller product yields. The chemoselectivity of the reaction is solvent dependent. Carboxylic acid 2b is observed as major product when the reaction takes place in acetonitrile, because of the facile overoxidation of the first formed alcohol product 2a. Instead the corresponding primary alcohol 2a becomes dominant in reactions performed in 2,2,2-trifluoroethanol (TFE). Polarity reversal of the hydroxyl moiety arising from the strong hydrogen bond donor ability of the latter solvent accounts for the unusual product chemoselectivity of the reaction. The significance of the current results in the context of light alkane oxidation is discussed.
Dantignana, Valeria,Company, Anna,Costas, Miquel
p. 470 - 477
(2020/09/09)

Transfer hydrogenation of ketones catalyzed by a trinuclear Ni(II) complex of a Schiff base functionalized N-heterocyclic carbene ligand
A new Schiff base-functionalized N-heterocyclic carbene ligand precursor 3-benzyl-1-[2-((2-hydroxy-benzylidene)-amino]-ethyl-3H-imidazol-1-ium bromide (3), and its trinuclear Ni(II) complex [LNiL-Ni-LNiL].2Br (4) where L = 2-[2-(3-benzylimidazol-1-yl) ethyliminomethyl]phenol, were synthesized via the solventless and free carbene routes respectively. Both compounds were characterized by spectroscopic and X-ray diffraction techniques. Single crystal XRD analysis of 4 showed that it is composed of a central square planar Ni(II) ion symmetrically linked to two distorted square planar Ni(II) ions via two bridging ligands. The central Ni(II) ion is only bound to the Schiff base moieties of the bridging ligands via the phenolate oxygen donor (O1) and imine nitrogen donor (N1) atoms in a trans [N^O^(Ni2+)^N^O] mode, whilst the carbene moieties of each bridging ligand and a tridentate L are coordinated in a distorted square planar CNHC-(Ni2+)^N^O^CNHC mode to stabilise each of the terminal Ni(II) ions. Complex 4 showed significant activity as a catalyst in the transfer hydrogenation of a range of aliphatic and aromatic ketones, at a catalyst concentration of 0.1 mol%. An excellent conversion up to 100% was achieved for aromatic ketones after 4 h.
Abubakar, Samaila,Ibrahim, Halliru,Bala, Muhammad D.
p. 276 - 282
(2018/10/02)

Synthesis of 3,5-Di-tert-butyl-1,2-dihydroxybenzene Derivatives and Their Effect on Free-Radical Oxidation of Hexane and Oxygen Activation Ability of Neutrophils
C6-Substituted derivatives of 3,5-di-tert-butyl-1,2-dihydroxybenzene have been synthesized, and their effect on radiation-induced free-radical oxidation of n-hexane and production of reactive oxygen and chlorine forms in neutrophils have been studied. It has been shown the introduction of the phenylhydrazone and phenylazomethine groups significantly increases the antioxidant activity of pyrocatechol derivatives. For six compounds, the ability to prevent the development of oxidative stress due to hyperproduction of active oxygen intermediates and HOCl/OCl? in neutrophils has been revealed.
Ksendzova,Ostrovskaya,Semenkova,Sorokin,Shishkanova,Shadyro
p. 391 - 398
(2019/05/01)

Application of Ni(II) complexes of air stable Schiff base functionalized N-heterocyclic carbene ligands as catalysts for the transfer hydrogenation of aliphatic ketones
New air stable N-heterocyclic carbene functionalized Schiff base ligands (L) of the type 2-[-2-[3-(R)imidazol-1-yl]ethyliminomethyl]phenol [R = methyl (2), 2-pyridylmethyl (3)] were synthesized and characterized by NMR, IR, MS, and CHN analysis. Single crystal X-ray structural analysis of their Ni(II) complexes revealed square planar arrangement of the chelating ligands coordinated in tridentate (2, C^N^O) and tetradentate (3, N^C^N^O) modes around the metal. The three new isolated and fully characterized complexes were utilized as catalysts for the catalytic transfer hydrogenation of aliphatic ketones in 2-propanol as solvent and source of hydrogen. Based on 0.2 mol% catalyst concentration, the complexes showed activity for aliphatic ketones and 100% conversion (turnover number of 500) for cyclohexanone and all the aromatic ketones tested.
Abubakar, Samaila,Bala, Muhammad D.
p. 2913 - 2923
(2018/09/27)

Hydrodeoxygenation of Sorbitol into Bio-Alkanes and -Alcohols Over Phosphated Ruthenium Molybdenum Catalysts
Biofuels such as renewable alkanes and higher alcohols have drawn considerable interests for the use in internal combustion engines. Especially, higher alcohols could be used as a blending agent for diesel fuels. Herein, carbon supported phosphated ruthenium-molybdenum (RuMoP) catalysts were employed in continuous trickle-bed reactor for converting sorbitol into renewable alkanes and higher alcohols. The results showed that RuMoP on an active carbon (AC) support presented a complete sorbitol conversion and high yields of alkanes and alcohols in gasoline and diesel range. Subsequently, carbon nanotube (CNT) supported RuMoP was prepared and studied in detail for comparison. RuMoP/CNT presented a low C?C bond cracking property in sorbitol conversion and high selectivity of C6 products in gas-phase (C6 alkane, 74.7 %) and oil-phase (C6 alkane and alcohols, 87.8 %). Finally, detailed characterizations (N2-adsorption, XRD, HRTEM, XPS, NH3-TPD, Py-IR spectrums, etc.) were performed over relevant catalysts (RuMoP/C and RuMoP/CNT) for correlating their catalytic and physicochemical properties.
Weng, Yujing,Wang, Tiejun,Wang, Chenguang,Liu, Qiying,Zhang, Yulong,Duan, Peigao,Wang, Longlong,Yin, Hongxing,Liu, Shijun,Ma, Longlong
p. 5046 - 5052
(2018/10/26)

Interplay between H-bonding and interpenetration in an aqueous copper(ii)-aminoalcohol-pyromellitic acid system: self-assembly synthesis, structural features and catalysis
Two new copper(ii) coordination compounds, [Cu(H1.5mdea)2]2(H2pma) (1a) and [{Cu2(μ-Hmdea)2}2(μ4-pma)]n·2nH2O (1b), were self-assembled at different temperatures from the same multicomponent reaction system, comprising copper(ii) nitrate, N-methyldiethanolamine (H2mdea), pyromellitic acid (H4pma), and potassium hydroxide. Products 1a and 1b were isolated as microcrystalline solids and fully characterized and their structures were established by single-crystal X-ray diffraction. Compound 1a features the bis-aminoalcohol(ate) monocopper(ii) units and H2pma2? anions that are multiply interconnected by strong H-bonds into a firm 2D H-bonded layer. Compound 1b reveals the bis-aminoalcoholate dicopper(ii) motifs that are interlinked by the μ4-pma4? spacers into a 3D + 3D interpenetrated metal-organic framework. From a topological perspective, both networks of 1a and 1b are uninodal and driven by similar 4-connected H2pma2? or pma4? nodes, but result in distinct sql and dia topologies, respectively. Compound 1a was applied as an efficient catalyst for two model cycloalkane functionalization reactions: (1) oxidation by H2O2 to form cyclic alcohols and ketones and (2) hydrocarboxylation by CO/H2O and S2O82? to form cycloalkanecarboxylic acids. The substrate scope, effects of various reaction parameters, selectivity and mechanistic features were also investigated.
Fernandes, Tiago A.,Kirillova, Marina V.,André, Vania,Kirillov, Alexander M.
p. 16674 - 16683
(2018/12/05)

METHOD FOR PRODUCING C5+ MONOALCOHOL
PROBLEM TO BE SOLVED: To provide a production method that makes it possible to obtain C5+ monoalcohol from a C5-6 sugar alcohol with high selectivity, in a single container with a catalyst put in. SOLUTION: In a method for producing C5+ monoalcohol, a catalyst comprises a catalyst grain in which a metal selected from Pt, Pd, and Rh and a metal/metal oxide selected from Ir-ReOx and Rh-MoOx are co-supported on SiO2 or TiO2. The method is characterized by putting hydrogen into a container from outside and heating it so that a selectivity of the C5+ monoalcohol to a compound having 5 or more carbon atoms is 40% or more. SELECTED DRAWING: Figure 1 COPYRIGHT: (C)2018,JPOandINPIT
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(2018/06/29)

Iridium Clusters Encapsulated in Carbon Nanospheres as Nanocatalysts for Methylation of (Bio)Alcohols
C?H methylation is an attractive chemical transformation for C?C bonds construction in organic chemistry, yet efficient methylation of readily available (bio)alcohols in water using methanol as sustainable C1 feedstock is limited. Herein, iridium nanocatalysts encapsulated in yolk–shell-structured mesoporous carbon nanospheres (Ir@YSMCNs) were synthesized for this transformation. Monodispersed Ir clusters (ca. 1.0 nm) were encapsulated in situ and spatially isolated within YSMCNs by a silica-assisted sol–gel emulsion strategy. A selection of (bio)alcohols (19 examples) was selectively methylated in aqueous phase with good-to-high yields over the developed Ir@YSMCNs. The improved catalytic efficiencies in terms of activity and selectivity together with the good stability and recyclability were contributable to the ultrasmall Ir clusters with oxidation chemical state as a consequence of the confinement effect of YSMCNs with interconnected nanostructures.
Liu, Qiang,Xu, Guoqiang,Wang, Zhendong,Liu, Xiaoran,Wang, Xicheng,Dong, Linlin,Mu, Xindong,Liu, Huizhou
p. 4748 - 4755
(2017/12/15)

Biomimetic oxidation of cyclic and linear alkanes: high alcohol selectivity promoted by a novel manganese porphyrin catalyst
A novel third-generation metalloporphyrin, chloro-5,10,15,20-tetrakis-(3′-bromine-4′-methoxyphenyl)-2,3,7,8,12,13,17,18-octabromoporphyrinatomanganese(iii), [MnIIIBr12T4(-OMe)PPCl], designated as MnBr12Por, was synthesized and characterized. The catalytic activity of the new manganese porphyrin was investigated in the oxidation of cyclohexane, adamantane and n-hexane by iodosylbenzene (PhIO) or iodobenzene diacetate (PhI(OAc)2) in comparison to the catalytic activity of the second-generation catalyst [MnIIIT4(-OMe)PPCl], designated as MnPor. All yields were based on oxidants. The MnBr12Por/PhIO system led to higher yields of cyclohexane oxidation products (45%) with high selectivity for cyclohexanol (80%) as compared to the MnPor/PhIO system (23% and 77%, respectively). Addition of imidazole to MnPor/PhIO increased the total product yield from 23 to 43%; addition of imidazole to MnBr12Por/PhIO did not alter the total product yield at all. For the MnPor/PhI(OAc)2 and MnBr12Por/PhI(OAc)2 systems, addition of imidazole increased the product yields from 19 to 45% and from 35 to 66%, respectively. Addition of water increased the total product yields during cyclohexane and adamantane oxidation for all the studied systems. In all cases, MnBr12Por performed better than MnPor.
Da Silva, Vinicius Santos,Dos Santos Vieira, Warleson Candido,Meireles, Alexandre Moreira,Ucoski, Geani Maria,Nakagaki, Shirley,Idemori, Ynara Marina,DeFreitas-Silva, Gilson
supporting information
p. 997 - 1006
(2017/02/10)

METHODS FOR PRODUCING BUTANOL
Methods and compositions for producing 1-butanol are described herein. In some examples, the methods can comprise, contacting a reactant comprising ethanol with a catalyst system, thereby producing a product comprising 1-butanol. The catalyst system can comprise, for example, an iridium catalyst and a nickel, copper, and/or zinc catalyst. The nickel, copper, and zinc catalysts can comprise nickel, copper, and/or zinc and a sterically bulky ligand.
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(2017/02/02)

Enzymatic kinetic resolution of aliphatic sec-alcohols by LipG9, a metagenomic lipase
Bioprospection for new enantioselective enzymes for application in organic synthesis is a prominent area of investigation in biocatalysis. In this context, here we present the evaluation of an immobilized lipase isolated from a metagenomic library (LipG9) for the enzymatic kinetic resolution (EKR) of aliphatic sec-alcohols, which are still challenging substrates, since low enantioselectivity values are usually observed for these resolutions. LipG9 was successfully employed in EKR of aliphatic alcohols, which were resolved with satisfactory conversions (19-59%) and enantiomeric excesses for alcohols (26-88%) and esters (30-96%) by transesterification reactions, demonstrating that its performance is equal to or better than commercially available enzymes for the same reaction.
Bandeira, Pamela T.,Alnoch, Robson C.,De Oliveira, Alfredo R.M.,De Souza, Emanuel M.,De O.P., Fábio,Krieger, Nadia,Piovan, Leandro
p. 58 - 63
(2016/01/30)

METHOD FOR PRODUCING HEXANOL/PENTANOL
PROBLEM TO BE SOLVED: To provide a method for producing hexanol/pentanol, which, in the presence of a catalyst, enables hexanol and pentanol to be obtained efficiently from cellulose and hemicellulose in cellulosic biomass, respectively. SOLUTION: Hexanol and pentanol are obtained by hydrolyzing, saccharizing, and at the same time hydrocracking cellulosic biomass in an aqueous phase in the presence of an Ir-Re(iridium-rhenium)-based catalyst and at a temperature at which cellulose/hemicellulose are decomposed, and by dissolving hexanol/pentanol in an oil phase comprising a liquid hydrocarbon arranged in proximity. SELECTED DRAWING: Figure 1 COPYRIGHT: (C)2016,JPOandINPIT
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(2017/01/23)

Fungal mediated kinetic resolution of racemic acetates to (R)-alcohols using Fusarium proliferatum
Fungal mediated kinetic resolution of seven acyclic/aromatic acetates was achieved using Fusarium proliferatum to furnish (R)-alcohols in high enantiomeric excess (>95%). The kinetic resolution was established as one-pot two-step de-esterification/oxidation biocatalytic process. Further, the preparative scale synthesis of (R)-(+)-1-phenylethanol was accomplished through de-esterification/oxidation of (±)-1-phenylethyl acetate using the whole cell of F. proliferatum NCIM 1105.
Jadhav, Dipesh D.,Patil, Harshal S.,Chaya, Patil S.,Thulasiram, Hirekodathakallu V.
p. 4563 - 4567
(2016/09/23)

ALKANE OXIDATION BY MODIFIED HYDROXYLASES
This invention relates to modified hydroxylases. The invention further relates to cells expressing such modified hydroxylases and methods of producing hydroxylated alkanes by contacting a suitable substrate with such cells.
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(2016/02/16)

From DNA to catalysis: A thymine-acetate ligated non-heme iron(III) catalyst for oxidative activation of aliphatic C-H bonds
A non-heme, iron(iii)/THA(thymine-1-acetate) catalyst together with H2O2 as an oxidant is efficient in oxidative C-H activation of alkanes. Although having a higher preference for tertiary C-H bonds, the catalyst also oxidizes aliphatic secondary C-H bonds into carbonyl compounds with good to excellent conversions. Based on the site selectivity of the catalyst and our mechanistic studies the reaction proceeds via an Fe-oxo species without long lived carbon centered radicals.
Al-Hunaiti, Afnan,R?is?nen, Minn?,Repo, Timo
supporting information
p. 2043 - 2046
(2016/02/05)

Cytochrome P450 oxygenases
Nucleic acids encoding cytochrome P450 variants are provided. The cytochrome P450 variants of have a higher alkane-oxidation capability, alkene-oxidation capability, and/or a higher organic-solvent resistance than the corresponding wild-type or parent cytochrome P450 enzyme. A preferred wild-type cytochrome P450 is cytochrome P450 BM-3. Preferred cytochrome P450 variants include those having an improved capability to hydroxylate alkanes and epoxidate alkenes comprising less than 8 carbons, and have amino acid substitutions corresponding to V78A, H236Q, and E252G of cytochrome P450 BM-3. Preferred cytochrome P450 variants also include those having an improved hydroxylation activity in solutions comprising co-solvents such as DMSO and THF, and have amino acid substitutions corresponding to T235A, R471A, E494K, and S1024E of cytochrome P450 BM-3.
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(2016/05/24)

Photooxygenation of alkanes by dioxygen with: P -benzoquinone derivatives with high quantum yields
Alkanes were oxygenated by dioxygen with p-benzoquinone derivatives such as p-xyloquinone in alkanes which are used as solvents to yield the corresponding alkyl hydroperoxides, alcohols and ketones under visible light irradiation with high quantum yields (Φ = 1000, 1600%). The photooxygenation is started by hydrogen atom abstraction from alkanes by the triplet excited states of p-benzoquinone derivatives as revealed by laser-induced transient absorption spectral measurements.
Ohkubo, Kei,Hirose, Kensaku,Fukuzumi, Shunichi
p. 731 - 734
(2016/07/06)

Solvent-Free Photooxidation of Alkanes by Dioxygen with 2,3-Dichloro-5,6-dicyano-p-benzoquinone via Photoinduced Electron Transfer
Photooxidation of alkanes by dioxygen occurred under visible light irradiation of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) which acts as a super photooxidant. Solvent-free hydroxylation of cyclohexane and alkanes is initiated by electron transfer from alkanes to the singlet and triplet excited states of DDQ to afford the corresponding radical cations and DDQ??, as revealed by femtosecond laser-induced transient absorption measurements. Alkane radical cations readily deprotonate to produce alkyl radicals, which react with dioxygen to afford alkylperoxyl radicals. Alkylperoxyl radicals abstract hydrogen atoms from alkanes to yield alkyl hydroperoxides, accompanied by regeneration of alkyl radicals to constitute the radical chain reactions, so called autoxidation. The radical chain is terminated in the bimolecular reactions of alkylperoxyl radicals to yield the corresponding alcohols and ketones. DDQ??, produced by the photoinduced electron transfer from alkanes to the excited state of DDQ, disproportionates with protons to yield DDQH2.
Ohkubo, Kei,Hirose, Kensaku,Fukuzumi, Shunichi
supporting information
p. 2255 - 2259
(2016/08/30)

Selective oxidation of n-hexane by Cu (II) nanoclusters supported on nanocrystalline zirconia catalyst
Cu (II) nanoclusters supported on nanocrystalline zirconia catalyst (with size ～15 nm), was prepared by using cationic surfactant cetyltrimethylammonium in a hydrothermal synthesis method. The catalyst was characterized by XRD, XPS, TGA, SEM, TEM, FTIR and ICP-AES. The catalyst was found to be efficient in selective oxidation of n-hexane to 2-hexanol. An n-hexane conversion of 55%, with a 2-hexanol selectivity of 70% was achieved over this catalyst in liquid phase, without the use of any solvent. The catalyst can be reused several times without any significant activity loss.
Acharyya, Shankha Shubhra,Ghosh, Shilpi,Adak, Shubhadeep,Singh, Raghuvir,Saran, Sandeep,Bal, Rajaram
p. 5816 - 5822
(2015/01/30)

New highly brominated Mn-porphyrin: A good catalyst for activation of inert C-H bonds
This work describes the synthesis and characterization of a novel third-generation catalyst 5,10,15,20-tetrakis-(4′-bromine-3′,5′-dimethoxyphenyl)-2,3,7,8,12,13,17,18-octabromoporphyrinatomanganese chloride [MnIIIBr12T3,5DMPP]Cl (Cat.2). The catalytic activity of Cat.2 in cyclohexane, adamantane, and n-hexane oxidation by iodosylbenzene (PhIO) or iodobenzene diacetate (PhI(OAc)2) was compared with the catalytic activity of [MnIIIT3,5DMPP]Cl (Cat.1), a second generation catalyst. The Cat.2/PhI(OAc)2 system led to higher yields of cyclohexane oxidation products (65%) with high selectivity for cyclohexanol (86%) as compared with Cat.1 (19% and 74%, respectively) and addition of water essentially did not alter total product yield. Addition of a small amount of imidazole to the Cat.1/PhIO system gave superior yields of cyclohexane oxidation products (64%) as compared with Cat.2 (52%). In all systems Cat.2 afforded significantly higher yields of 2-adamantanol, a product with great commercial value compared with 1-adamantanol. n-Hexane oxidation gave low total product yield; Cat.2 was more selective for alcohol products (2-hexanol and 3-hexanol).
Santos Da Silva, Vinicius,Nakagaki, Shirley,Ucoski, Geani Maria,Idemori, Ynara Marina,DeFreitas-Silva, Gilson
p. 106589 - 106598
(2016/01/08)

Revisiting cytochrome P450-mediated oxyfunctionalization of linear and cyclic alkanes
Cytochrome P450 monooxygenases (CYPs) of the CYP153 family catalyse terminal hydroxylation of n-alkanes. Alkane hydroxylating mutants of self-sufficient CYP102A1 have also been described. We evaluated two CYP153s (a three-component system and a fused self-sufficient CYP), wildtype CYP102A1 and nine CYP102A1 mutants, for the conversion of three cycloalkanes (C6, C7 and C8) and three n-alkanes (C6, C8 and C10) using whole cells (WCs) and crude cell-free extracts (CFEs). The aim was to identify substrate-enzyme combinations that give high product titres and space-time yields (STYs). Comparisons were made using total turnover numbers (TTNs) and turnover frequencies (TOFs) to normalize for CYP expression. Reactions were carried out using high enzyme and substrate concentrations compatible with high STYs. Under these conditions CYP102A1 and the double R47L,Y51F mutant, although not regioselective, performed better on all substrates in terms of product titres over 8 h, and thus STYs and TTNs, than heavily mutated variants that have been reported to give very high TOFs. CYP153A6, with its ferredoxin (Fdx) and ferredoxin reductase (FdR), emerged as the superior catalyst for conversion of n-alkanes. In addition to its excellent regioselectivity it also gave the highest final product titres and STYs in WC conversions of hexane and octane. Interaction with FdR and Fdx initially limited performance in CFEs, but with additional FdR and Fdx gave 1-octanol titres of 50 mmol·LBRM-1 and TTNs exceeding 12,000 over 18 h, rivalling results reported with self-sufficient CYPs. Selecting biocatalysts for application requires caution, since experimental conditions such as amount of substrate added and solubility as well as cofactor dependence and regeneration can have a profound effect on catalyst performance, while stability and efficiency with regard to cofactor usage (coupling efficiency) are at least as important as TOFs when high product titres and STYs are the target.
Pennec, Aliz,Jacobs, Cheri L.,Opperman, Diederik J.,Smit, Martha S.
supporting information
p. 118 - 130
(2015/01/30)

Composites of [γ-H2PV2W10O40]3- and [α-SiW12O40]4- supported on Fe2O3 as heterogeneous catalysts for selective oxidation with aqueous hydrogen peroxide
Composites of [γ-H2PV2W10O40]3- and [α-SiW12O40]4- supported on Fe2O3 (PV2-SiW12/Fe2O3, in particular, the molar ratio of PV2/SiW12 = 1/1) could act as effective and reusable heterogeneous catalysts for selective oxidation with aqueous hydrogen peroxide. In the presence of PV2-SiW12/Fe2O3, various kinds of organic substrates such as alkenes, sulfides, arenes, and alkanes could selectively be converted into the corresponding oxygenated products in moderate to high yields. The observed catalyses for the present oxidations were intrinsically heterogeneous, and PV2-SiW12/Fe2O3 could be reused at least three times for each oxidation (epoxidation, sulfoxidation, and arene hydroxylation) without appreciable losses of the high catalytic performance.
Wang, Ye,Kamata, Keigo,Ishimoto, Ryo,Ogasawara, Yoshiyuki,Suzuki, Kosuke,Yamaguchi, Kazuya,Mizuno, Noritaka
p. 2602 - 2611
(2015/05/13)

Catalytic oxidation of alkanes by a (salen)osmium(VI) nitrido complex using H2O2 as the terminal oxidant
The osmium(vi) nitrido complex, [OsVI(N)(L)(CH3OH)]+ (1, L = N,N′-bis(salicylidene)-o-cyclohexyldiamine dianion) is an efficient catalyst for the oxidation of alkanes under ambient conditions using H2O2 as the oxidant. Alkanes are oxidized to the corresponding alcohols and ketones, with yields up to 75% and turnover numbers up to 2230. Experimental and computational studies are consistent with a mechanism that involves O-atom transfer from H2O2 to [OsVI(N)(L)]+ to generate an [OsVIII(N)(O)(L)]+ active intermediate.
Chen, Man,Pan, Yi,Kwong, Hoi-Ki,Zeng, Raymond J.,Lau, Kai-Chung,Lau, Tai-Chu
supporting information
p. 13686 - 13689
(2015/09/02)

Efficient one-pot production of 1,2-propanediol and ethylene glycol from microalgae (Chlorococcum sp.) in water
The catalytic valorization of microalgae, a sustainable feedstock to alleviate dependence on fossil fuel and offset greenhouse gases emissions, is of great significance for production of biofuels and value-added chemicals from aquatic plants. Here, an interesting catalytic process is reported to convert microalgae (Chlorococcum sp.) into 1,2-propanediol (1,2-PDO) and ethylene glycol (EG) in water over nickel-based catalysts. The influences of reaction temperature, initial H2 pressure and reaction time on the product distribution were systematically investigated by using a batch reactor. Under optimal reaction conditions (at 250 °C for 3 h with 6.0 MPa of H2 pressure), microalgae were directly and efficiently converted over a Ni-MgO-ZnO catalyst and the total yield of polyols was up to 41.5%. The excellent catalytic activity was attributed to the smaller size and better dispersion of Ni particles on the MgO-ZnO supporter based on the characterization results as well as its tolerance to nitrogen-containing compounds. Besides, the reaction pathway was proposed based on the formation of reaction intermediates and the results of model compound conversion.
Miao,Zhu,Wang,Tan,Wang,Liu,Kong,Sun
p. 2538 - 2544
(2015/04/22)

Application of three-legged piano-stool cyclopentadienyl-N-heterocyclic carbene iron(II) complexes as in situ catalysts for the transfer hydrogenation of ketones
A one pot system has been developed based on nine related 1,3-dialkylated imidazolium salts for the in situ generation of N-heterocyclic carbene iron(II) complexes in which the complexes were directly tested as catalysts for the transfer hydrogenation of ketones. This is a simplified reproducible process that aims to eliminate unnecessary purification steps for the isolation of such catalysts prior to application. Complexes 10-12 have been prepared under similar conditions, isolated and structurally characterized by spectroscopic and crystallographic methods. Solid state structures of the three complexes were similar and showed distorted octahedral three-legged piano stool geometry around each iron center similar to reported complexes bearing related ligands. As a basis for comparison with the in situ catalyzed systems, the isolated complexes were also tested as catalysts for the transfer hydrogenation of ketones. As a result, under optimized reaction conditions, all the in situ generated catalysts were found to provide excellent activities similar to those based on the isolated complexes with moderate to excellent conversions to the desired alcohol products. Turn over numbers up to 200 at a conversion of 100% was recorded for a wide range of aliphatic, aromatic and cyclic ketones.
Bala, Muhammad D.,Ikhile, Monisola I.
p. 98 - 105
(2014/03/21)

Peroxidative oxidation of cyclic and linear hexane catalysed by supported iron complexes under mild and sustainable conditions
The development of economical heterogeneous catalysts based on first row transition metal complexes that work under mild and sustainable reaction conditions in the activation of CH bonds is very important. Herein, commercially available iron(II) and iron(III) acetylacetonate were immobilised onto amine functionalised economical and environmentally acceptable solid porous supports: hexagonal mesoporous silica and activated carbon. The materials prepared by this very simple and straightforward methodology were characterised by elemental analysis, ICP-AES, FTIR, isotherms of adsorption at 77 K and thermogravimetry. It showed that both porous materials were conveniently functionalised with amine groups and that the iron metal complexes could be effectively anchored onto these materials. The immobilised iron salts were active as heterogeneous catalysts in the oxidation of cyclohexane and n-hexane at room temperature with hydrogen peroxide, giving the respective alcohols and ketones. They could also be recycled at least two times without loss of catalytic activity in the oxidation of cyclohexane. In the oxidation of n-hexane this was only true for the anchored Fe(II) salts. In the oxidation of cyclohexane, both iron salts are more active heterogeneous catalysts anchored onto the activated carbons than onto the hexagonal mesoporous silicas. The opposite is observed in the oxidation of n-hexane. The heterogeneous catalysts reported herein are economical and work under mild reaction conditions and thus could be valuable for the improvement of the sustainability and environmental impact of processes currently used in industry.
Silva, Ana Rosa,Botelho, Jo?o
p. 171 - 178
(2013/12/04)

Evidence that steric factors modulate reactivity of tautomeric iron-oxo species in stereospecific alkane C-H hydroxylation
A new iron complex mediates stereospecific hydroxylation of alkyl C-H bonds with hydrogen peroxide, exhibiting excellent efficiency. Isotope labelling studies provide evidence that the relative reactivity of tautomerically related oxo-iron species responsible for the C-H hydroxylation reaction is dominated by steric factors. This journal is The Royal Society of Chemistry.
Mitra, Mainak,Lloret-Fillol, Julio,Haukka, Matti,Costas, Miquel,Nordlander, Ebbe
supporting information
p. 1408 - 1410
(2014/02/14)

A significant enhancement of catalytic activities in oxidation with H 2O2 over the TS-1 zeolite by adjusting the catalyst wettability
Hydrophilic TS-1 (H-TS-1) with rich hydroxyl groups, which were confirmed by 29Si and 1H NMR techniques, exhibits much higher activities in the oxidation than conventional TS-1. This phenomenon is strongly related to the unique features of high enrichment of H2O2 on H-TS-1.
Wang, Liang,Sun, Jing,Meng, Xiangju,Zhang, Weiping,Zhang, Jian,Pan, Shuxiang,Shen, Zhe,Xiao, Feng-Shou
supporting information
p. 2012 - 2014
(2014/03/21)

Application of ferrocenylimidazolium salts as catalysts for the transfer hydrogenation of ketones
Ferrocenylimidazolium salts with methylene and phenyl groups bridging the ferrocenyl and alkylimidazolium moieties were synthesized and characterized by spectroscopic and analytical methods. Crystal structures of two new compounds are also reported. Cyclic voltammetry was used to analyze the influence of the two bridging groups or spacers on electrochemical properties of the salts relative to the shifts in the formal electrode or peak potentials (E0 or E1/2) of the ferrocene/ferrocenium redox couple. Results from this study showed that all the salts exhibited higher electrode potentials relative to ferrocene, which is due to the electron-withdrawing effect of the imidazolium ion on the ferrocenyl moiety. Application of the salts as catalysts in transfer hydrogenation of ketones resulted in high conversion of saturated ketones to corresponding alcohols and turnover numbers as high as 1880. The catalysts were chemoselective towards reduction of the C=C bonds of conjugated 3-penten-2-one and 4-hexen-3-one to yield saturated ketones, while unconjugated 5-hexen-2-one was hydrogenated to an unsaturated alcohol. Copyright
Ikhile, Monisola I.,Bala, Muhammad D.,Nyamori, Vincent O.,Ngila, J. Catherine
p. 98 - 108
(2013/03/13)

Iron(III) chloride-benzotriazole adducts with trigonal bipyramidal geometry: Spectroscopic, structural and catalytic studies
The reactions of FeCl3 with benzotriazole (btaH), 1-methylbenzotriazole (Mebta), 5,6-dimethylbenzotriazole (5,6Me2btaH) and 5-chlorobenzotriazole (5ClbtaH) were studied in non-polar solvents. The new solid complexes [FeCl3(btaH)2] (1), [FeCl 3(Mebta)2] (2), [FeCl3(5,6Me 2btaH)2] (3) and [FeCl3(5ClbtaH) 2]·2(5ClbtaH) (4) have been isolated. The structures of the complexes have been determined by single-crystal, X-ray crystallography. The structures of 1-4 consist of mononuclear, high-spin 5-coordinate molecules; in addition, the crystal structure of 4 contains two lattice 5ClbtaH molecules per [FeCl3(5ClbtaH)2] unit. The coordinated benzotriazole molecules behave as monodentate ligands with their ligated atom being the nitrogen of the position 3 of the azole ring. The geometry at iron(III) is trigonal bipyramidal with the chlorido ligands occupying the equatorial sites. The crystal structures of the complexes are stabilized by stacking interactions and H bonds (for 1, 3 and 4 only). The new complexes were characterized by elemental analyses, magnetic susceptibilities at room temperature and spectroscopic (IR, far-IR, solid-state electronic UV/VIS/near-IR, 57Fe-Mo?ssbauer, EPR only for complex 4) methods. All data are discussed in terms of the nature of bonding and the known structures. Complexes 1, 2 and 4 have been tested as homogeneous (MeCN) oxidation catalysts in the presence of the "green" H2O2 oxidant; they display moderate to high catalytic activity in the oxidation of several alkenes, cyclohexane and n-hexane, which is described in detail.
Anastasiadis, Nikolaos C.,Bilis, George,Plakatouras, John C.,Raptopoulou, Catherine P.,Psycharis, Vassilis,Beavers, Christine,Teat, Simon J.,Louloudi, Maria,Perlepes, Spyros P.
p. 189 - 202
(2013/10/08)

Control of the selectivity in multi-functional group molecules using supported gold-palladium nanoparticles
The oxidation of 2-hexen-1-ol and 1-hexen-3-ol with air has been studied using supported gold, palladium and gold-palladium catalysts. The main aim was to determine if either the alcohol or alkene functional group can be oxidised selectively. However, based on the reaction products observed (2-hexen-1-ol forms 2-hexene, hexanal, (E)-2-hexenal, (E)-3-hexen-1-ol, 4-hexen-1-ol and (E)-2-hexanoic acid. 1-Hexen-3-ol forms 1-hexene, 3-hexanone, 1-hexen-3-one and 3-hexenol), the main pathway in these reactions is isomerisation and, in addition, significant yields of the products are due to a disproportionation reaction. Controlling the selectivity in molecules with multiple function groups by manipulating the catalyst composition and reaction conditions can promote or hinder the various reaction pathways, thereby increasing the selectivity to the desired oxidation products.
Alshammari, Hamed,Miedziak, Peter J.,Morgan, David J.,Knight, David W.,Hutchings, Graham J.
p. 1244 - 1254
(2013/06/26)

Hydrogenation and redox isomerization of allylic alcohols catalyzed by a new water-soluble Pd-tetrahydrosalen complex
For applications in aqueous media, sulfonated tetrahydrosalen (sulfosalan, HSS) was synthesized by sulfonation of tetrahydrosalen in fuming sulfuric acid. The Pd(II) complex of this ligand, [Pd(HSS)], showed outstanding activity in hydrogenation and redox isomerization of allylic alcohols in homogeneous aqueous solutions or in aqueous-organic biphasic systems (for oct-1-en-3-ol TOF(hydrogenation) = 1580 h-1, TOF(redox isomerization) = 400 h -1). DFT calculations revealed that H2 is activated heterolytically, resulting in a Pd(II)-hydride complex, [Pd(H)(HSS-Hphen)], in which one of the phenolate oxygens is protonated. Both hydrogenation and redox isomerization take place via concerted transfer of a proton and a hydride from the hydrogenated catalyst to the allylic alcohol.
Voronova, Krisztina,Purgel, Mihaly,Udvardy, Antal,Benyei, Attila C.,Katho, Agnes,Joo, Ferenc
p. 4391 - 4401
(2013/09/02)

Oxidation of cyclohexane by transition-metal complexes with biomimetic ligands
This work reports the catalytic activity, in homogeneous phase, of transition-metal complexes of the first-row (V(IV), Mn(III), Fe(III) Co(III) and Cu(II)) with biomimetic Schiff base ligands with N2O2 coordination sphere, as well as an N4 (Fe(II)), in the room-temperature oxidation of cyclohexane using environmentally benign reagents: hydrogen peroxide (30 wt%) as the oxygen source and acetonitrile as the solvent. Nitric acid is also used as promoter of the oxidation reaction. The structure of the ligands is confirmed by FTIR, 1H NMR and high-resolution ESI mass spectrometry. The corresponding transition metal complexes are characterized by elemental analysis, high resolution ESI mass spectrometry, FTIR and UV-vis. Cyclohexanone and cyclohexanol are the main products of the oxidation of cyclohexane, obtained when the following complexes are used as homogeneous catalysts in only 1 mol% based on the substrate: VO(IV), Fe(III) and Cu(II) complexes with the N2O2 Schiff base, new Fe(II) complex with the Schiff base with N4 coordination sphere and commercial [VO(acac)2] with O4 coordination sphere. The Fe(III) complex with N2O2 Schiff base ligand ([Fe(salhd)Cl]) is the homogeneous catalyst with highest activity, which could be further enhanced by the addition of methyl electron donating groups to the N2O2 Schiff base aldehyde fragment (reaching 46% oxygenate yields and 45 turnover numbers). Cyclooctane and n-hexane could also be oxidized to the corresponding ketones and alcohols with higher turnover numbers than cyclohexane by the Fe(III) complex with N2O2 Schiff base ligand.
Silva, Ana Rosa,Mour?o, Teresa,Rocha, Jo?o
p. 81 - 86
(2013/08/24)

Hydrocarbon oxidation catalyzed by manganese and iron complexes with the hexadentate ligand N,N′-di(ethylacetate)-N,N′-bis(2-pyridyl-methyl)- 1, 2-ethanediamine
Analogs of recently reported manganese and iron catalysts for alkene and alkane oxidation reactions have been prepared with the potentially hexadentate ligand N,N′-di(ethylacetate)-N,N′-bis(2-pyridylmethyl)-1, 2-ethanediamine (debpn). The Mn(II) and Fe(II) complexes, which were previously found to be hepta-coordinate in the solid state, are capable of catalyzing alkene epoxidation and aliphatic C-H activation reactions, although these activities are inferior to those of related complexes with less coordinating ligands. The hydrocarbon oxidation catalyzed by iron is more severely disrupted. Cyclic voltammetry indicates that the +2 oxidation states for both debpn complexes' metal ions are stabilized by the two additional chelate arms. Product analysis of the C-H activation and olefin epoxidation chemistries suggest that ligand-substrate steric interactions may exert additional inhibitory effects on the reactivity for the manganese catalysts.
Zhang, Qiao,Goldsmith, Christian R.
p. 301 - 306
(2013/10/22)

One-pot conversion of sugar and sugar polyols to n-alkanes without C-C dissociation over the Ir-ReOx/SiO2 catalyst combined with H-ZSM-5
High (≥95% C) yields of n-hexane and n-pentane were obtained by hydrogenolysis of aqueous sorbitol and xylitol, respectively, at 413-443 K by using the Ir-ReOx/SiO2 catalyst combined with H-ZSM-5 as a cocatalyst and n-dodecane as a cosolvent. The direct production of n-hexane from glucose or cellobiose can be achieved by using the same system. The catalyst can be reused simply by the removal of the n-dodecane phase, which contains the product alkane, and the addition of fresh n-dodecane and substrate.
Chen, Kaiyou,Tamura, Masazumi,Yuan, Zhenle,Nakagawa, Yoshinao,Tomishige, Keiichi
p. 613 - 621
(2013/07/27)

PHOSPHO-AMINO PINCER-TYPE LIGANDS AND CATALYTIC METAL COMPLEXES THEREOF
The present invention provides phospho-amino pincer-type ligands, metal complexes thereof, and catalytic methods comprising such metal complexes.
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(2013/02/27)

Ruthenium(II) pincer complexes with oxazoline arms for efficient transfer hydrogenation reactions
Well-defined PNNCN pincer ruthenium complexes bearing both strong phosphine and weak oxazoline donors were developed. These easily accessible complexes exhibit significantly better catalytic activity in transfer hydrogenation of ketones compared to their PN3P analogs. These reactions proceed under mild and base-free conditions via protonation- deprotonation of the 'NH' group in the aromatization-dearomatization process.
Chen, Tao,He, Li-Peng,Gong, Dirong,Yang, Limin,Miao, Xiaohe,Eppinger, J?rg,Huang, Kuo-Wei
supporting information; experimental part
p. 4409 - 4412
(2012/09/25)

Transition metal free transfer hydrogenation of ketones promoted by 1,3-diarylimidazolium salts and KOH
An efficient transition metal free and greener catalytic system was developed for the selective transfer hydrogenation of saturated ketones to alcohols. This was achieved by the use of 1,3-diarylimidazolium salts in the presence of KOH as a promoter for the reaction. When the range of substrates was expanded to include unsaturated ketones, selective reduction of the double bond occurred. The catalyst efficiency was comparable to some established transition metal catalyzed systems. The current system utilizes mild aerobic reaction conditions compared to the inert atmosphere conditions required for the corresponding metal based systems.
Ikhile, Monisola Itohan,Nyamori, Vincent Onserio,Bala, Muhammad Dabai
p. 4925 - 4928,4
(2020/07/31)

Borenium ion catalyzed hydroboration of alkenes with N-heterocyclic carbene-boranes
Treatment of alkenes such as 3-hexene, 3-octene, and 1-cyclohexyl-1-butene with the N-heterocyclic carbene (NHC)-derived borane 2 and catalytic HNTf 2 (Tf = trifluoromethanesulfonyl (CF3SO2)) effects hydroboration at room temperature. With 3-hexene, surprisingly facile migration of the boron atom from C(3) of the hexyl group to C(2) was observed over a time scale of minutes to hours. Oxidative workup gave a mixture of alcohols containing 2-hexanol as the major product. A similar preference for the C(2) alcohol was observed after oxidative workup of the 3-octene and 1-cyclohexyl-1-butene hydroborations. NHC-borenium cations (or functional equivalents) are postulated as the species that accomplish the hydroborations, and the C(2) selective migrations are attributed to the four-center interconversion of borenium cations with cationic NHC-borane-olefin π-complexes.
Prokofjevs, Aleksandrs,Boussonniere, Anne,Li, Linfeng,Bonin, Helene,Lacote, Emmanuel,Curran, Dennis P.,Vedejs, Edwin
supporting information; experimental part
p. 12281 - 12288
(2012/09/22)

Single site anchored novel Cu(II) catalysts for selective liquid-gas phase O2 oxidation of n-alkanes
The pentacoordinate schiff-base trialkoxysilane Cu(II) complexes, i.e. Cu[Sal(PMeOSi)DPTA], (III-a) and Cu[Cl-Sal(PMeOSi)DPTA], (III-b) were synthesized and covalently anchored on SiO2 and Al2O 3 matrixes as supported hybrid catalysts (i.e. III-a/SiO2 as Catal.-1, III-b/SiO2 as Catal.-2, III-a/Al2O 3 as Catal.-3 and III-b/Al2O3 as Catal.-4). The characterization of supported Cu(II) complexes were performed with SEM-EDX, TGA, ICP, FT-IR and EPR analysis. Catalytic tests were conducted in the oxidation (O2) of n-alkanes under relatively mild conditions, in a batch rocking type reactor. Remarkable high catalytic TONs, from 1468 up to 2422, were observed. Catal.-2 provided the best overall yield, 25.2% with 92% selectivity for n-hexane and 20.1% with 75% selectivity for n-heptane. A 20% improvement in the yields was obtained with PCA as co-catalyst. The impact of both C- and O- centred radical traps were also assessed in order to establish a radical mechanism.
Mishra, Gopal S.,Kumar, Anil,Tavares, Pedro B.
experimental part
p. 125 - 132
(2012/05/20)

Oxidative functional group transformations with hydrogen peroxide catalyzed by a divanadium-substituted phosphotungstate
A divanadium-substituted phosphotungstate TBA4[γ-PW 10O38V2(μ-OH)(μ-O)] (I, TBA = tetra-n-butylammonium) reacts with one equivalent H+ to form a bis-μ-hydroxo species [γ-PW10O38V 2(μ-OH)2]3- (I′) in organic media. The strong electrophilic oxidants such as [γ-PW10O 38V2(μ-OH)(μ-OOH)]3- (II) and [γ-PW10O38V2(μ-η2: η2-O2)]3- (III) are formed by the reaction of the bis-μ-hydroxo species with H2O2. In the presence of I and H+, H2O2-based oxidations such as (i) epoxidation of alkenes (17 examples including electron-deficient ones), (ii) hydroxylation of alkanes (11 examples), and (iii) oxidative bromination of alkenes, alkynes, and aromatics with Br- as a bromo source (12 examples including chlorination) chemo-, diastereo-, and regioselectively proceed to give the corresponding oxidized products in moderate to high yields with high efficiencies of H2O2 utilization.
Mizuno, Noritaka,Kamata, Keigo,Yamaguchi, Kazuya
scheme or table
p. 157 - 161
(2012/06/18)

Reduction of Cr(VI) polymerization catalysts by non-olefinic hydrocarbons
The Phillips Cr(VI)/silica catalyst, which is widely used for commercial ethylene polymerization, is usually considered to be reduced to a lower-valent active Cr species in the reactor upon contact with ethylene or other α-olefin monomers. In this paper, however, the case is presented that Cr(VI) is actually quite reactive with other hydrocarbons to which it is also often exposed, including alkanes and aromatics. Redox products from these reactions are identified, and the effect on catalyst polymerization activity and polymer character is described.
Schwerdtfeger, Eric,Buck, Richard,McDaniel, Max
body text
p. 91 - 99
(2012/06/01)

Iridium NHC based catalysts for transfer hydrogenation processes using glycerol as solvent and hydrogen donor
A series of iridium and ruthenium N-heterocyclic carbene based catalysts of general formula [IrI2(AcO)(bis-NHC)] or [Ru(η6-arene) (NHC)CO3] have been tested in the reduction of several organic carbonyl compounds using glycerol as solvent and hydrogen donor, by the transfer hydrogenation methodology. The Ir(III) complexes with a chelating bis-NHC ligand and sulfonate groups were the most efficient, due to their solubility in the reaction media and to the strong electron-donor properties of the bis-carbene ligands. The same two catalysts were moderately active in the reduction of olefins and alkynes and, more remarkably, show excellent chemoselectivity in the reduction of the alkenic double bond of α,β-unsaturated ketones, a valuable process for which glycerol had never been used before.
Azua, Arturo,Mata, Jose A.,Peris, Eduardo
experimental part
p. 5532 - 5536
(2011/12/13)

PROCESS INCLUDING HYDROGENOLYSIS OF BIOMASS FOLLOWED BY DEHYDROGENATION AND ALDOL CONDENSATION FOR PRODUCING ALKANES
A method comprises providing a bio-based feedstock; contacting the bio-based feedstock with a solvent in a hydrolysis reaction to form an intermediate stream comprising carbohydrates; contacting the intermediate stream with an aqueous phase reforming catalyst to form a plurality of oxygenated intermediates, wherein a first portion of the oxygenated intermediates are recycled to form the solvent; and contacting at least a second portion of the oxygenated intermediates with a condensation catalyst comprising a base functionality to form a fuel blend.
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(2011/12/02)