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Zirconium Oxide Supported Palladium Nanoparticles as a Highly Efficient Catalyst in the Hydrogenation–Amination of Levulinic Acid to Pyrrolidones
The selective hydrogenation–amination of levulinic acid into pyrrolidones is regarded as one of the most important reactions to transform biomass-derived lignocellulose feedstocks into valuable chemicals. Here we report on ZrO2-supported Pd nanoparticles as a highly active, chemoselective, and reusable catalyst for the hydrogenation–amination of levulinic acid with H2 and various amines under mild reaction conditions. The Pd/ZrO2 catalyst exhibited a marked increase in activity compared with conventional Pd catalysts and a significant enhancement in pyrrolidone selectivity. The excellent catalytic performances are reasonably attributed to the ZrO2 support, which has strong Lewis acidity to enhance the hydrogenation–amination reaction and hinder side reactions.
Zhang, Jian,Xie, Bin,Wang, Liang,Yi, Xianfeng,Wang, Chengtao,Wang, Guoxiong,Dai, Zhifeng,Zheng, Anmin,Xiao, Feng-Shou
p. 2661 - 2667
(2017)
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IVESTIGATIONS OF THE MECHANISM OF THE Rh/Cu- AND Rh-CATALYZED OXIDATION OF TERMINAL OLEFINS WITH O2
The mechanism of the Rh(III9-catalyzed oxidation of 1-hexene to 2-hexanone, both with and without a Cu(II) co-catalyst, is investigated.In the absence of Cu(II), only one oxygen atom of dioxygen is found to be incorporated into ketone product.This contrasts with the previously reported observation that in the presence of the Cu(II) co-catalyst both oxygen atoms of O2 are incorporated into product.Similaly, the Rh(III) catalyst without Cu(II) isomerizes 1-hexene to a large extent, in contrast to the previously reported Rh/Cu catalyst system.Both acetone and water are found to be produced continously when isopropyl alcohol is the absence of Cu(II), while neither are formed continuosly when Cu(II) is present.Furthermore, itis shown that H"O" and t-BuOOH may be used as the 1-hexene oxidant under anaerobic conditions in the presence or absence of Cu(II), producing 2-ketone.These observations are incorporated into tentative mechanisms which specify key roles for copper that lead to differences in reactivity.
Drago, Russell S.,Zuzich, Anne,Nyberg, Eric D.
p. 2898 - 2903
(1985)
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A Cyclometalated NHC Iridium Complex Bearing a Cationic (η5-Cyclopentadienyl)(η6-phenyl)iron Backbone**
Nucleophilic substitution of [(η5-cyclopentadienyl)(η6-chlorobenzene)iron(II)] hexafluorophosphate with sodium imidazolate resulted in the formation of [(η5-cyclopentadienyl)(η6-phenyl)iron(II)]imidazole hexafluorophosphate. The corresponding dicationic imidazolium salt, which was obtained by treating this imidazole precursor with methyl iodide, underwent cyclometallation with bis[dichlorido(η5-1,2,3,4,5-pentamethylcyclopentadienyl]iridium(III) in the presence of triethyl amine. The resulting bimetallic iridium(III) complex is the first example of an NHC complex bearing a cationic and cyclometallated [(η5-cyclopentadienyl)(η6-phenyl)iron(II)]+ substituent. As its iron(II) precursors, the bimetallic iridium(III) complex was fully characterized by means of spectroscopy, elemental analysis and single crystal X-ray diffraction. In addition, it was investigated in a catalytic study, wherein it showed high activity in transfer hydrogenation compared to its neutral analogue having a simple phenyl instead of a cationic [(η5-cyclopentadienyl)(η6-phenyl)iron(II)]+ unit at the NHC ligand.
Malchau, Christian,Milbert, Tom,Eger, Tobias R.,Fries, Daniela V.,Pape, Pascal J.,Oelkers, Benjamin,Sun, Yu,Becker, Sabine,Prosenc, Marc H.,Niedner-Schatteburg, Gereon,Thiel, Werner R.
p. 15208 - 15216
(2021)
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Organozirconium Complex with Keggin-Type Mono-Aluminum-Substituted Silicotungstate: Synthesis, Molecular Structure, and Catalytic Performance for Meerwein–Ponndorf–Verley Reduction
Abstract: The organozirconium complex with α-Keggin-type mono-aluminum-substituted silicotungstate, [(n-C4H9)4N]6[α-SiW11Al(OH)2O38ZrCp2]2·2H2O (TBA–Si–Al–Zr) was synthesized by the reaction of Cp2Zr(OTf)2·THF (or Cp2ZrCl2) with [(n-C4H9)4N]4K0.5H0.5[α-SiW11{Al(OH2)}O39]·H2O in acetonitrile. This compound showed high catalytic activities for Meerwein–Ponndorf–Verley reduction of ketones with 2-propanol in both homogeneous and heterogeneous system. Graphical Abstract: [Figure not available: see fulltext.]
Kato, Chika Nozaki,Unno, Wataru,Kato, Sakie,Ogasawara, Tsukasa,Kashiwagi, Toshifumi,Uno, Hidemitsu,Suzuki, Kosuke,Mizuno, Noritaka
p. 2119 - 2128
(2016)
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A novel and efficient N-doping carbon supported cobalt catalyst derived from the fermentation broth solid waste for the hydrogenation of ketones via Meerwein–Ponndorf–Verley reaction
Most of the non-noble metal catalysts used for the Meerwein–Ponndorf–Verley (MPV) reaction of carbonyl compounds rely on the additional alkaline additives during preparation to achieve high efficiency. To solve this problem, in this work, we prepared a novel N-doped carbon supported cobalt catalyst (Co@CN), in which the carriers were derived from the nitrogen-rich organic waste, i.e., oxytetracycline fermentation residue (OFR, obtained from oxytetracycline refining workshop). No additional nitrogen sources were used during preparation. The results showed that inherent nitrogen in OFR could provide N-containing basic sites, and formed Co-N structures via coordinating with cobalt. The Co-N sites together with the coexisting Co(0) cooperated to catalyze the conversion of ethyl levulinate (EL) to γ-valerolactone (GVL) by MPV reaction. Co(0) dominated the activation of H in isopropanol, while Co-N dominated the formation of the six-membered ring transition state.
Chen, Yuxin,He, Runxia,Liu, Quansheng,Yao, Xuefeng,Zhou, Huacong
(2021/12/10)

Regiodivergent Reductive Opening of Epoxides by Catalytic Hydrogenation Promoted by a (Cyclopentadienone)iron Complex
The reductive opening of epoxides represents an attractive method for the synthesis of alcohols, but its potential application is limited by the use of stoichiometric amounts of metal hydride reducing agents (e.g., LiAlH4). For this reason, the corresponding homogeneous catalytic version with H2 is receiving increasing attention. However, investigation of this alternative has just begun, and several issues are still present, such as the use of noble metals/expensive ligands, high catalytic loading, and poor regioselectivity. Herein, we describe the use of a cheap and easy-To-handle (cyclopentadienone)iron complex (1a), previously developed by some of us, as a precatalyst for the reductive opening of epoxides with H2. While aryl epoxides smoothly reacted to afford linear alcohols, aliphatic epoxides turned out to be particularly challenging, requiring the presence of a Lewis acid cocatalyst. Remarkably, we found that it is possible to steer the regioselectivity with a careful choice of Lewis acid. A series of deuterium labeling and computational studies were run to investigate the reaction mechanism, which seems to involve more than a single pathway.
De Vries, Johannes G.,Gandini, Tommaso,Gennari, Cesare,Jiao, Haijun,Pignataro, Luca,Stadler, Bernhard M.,Tadiello, Laura,Tin, Sergey
p. 235 - 246
(2022/01/03)

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)

Direct use of the solid waste from oxytetracycline fermentation broth to construct Hf-containing catalysts for Meerwein-Ponndorf-Verley reactions
The oxytetracycline fermentation broth residue (OFR) is an abundant solid waste in the fermentation industry, which is hazardous but tricky to treat. The resource utilization of the waste OFR is still challenging. In this study, a novel route of using OFR was proposed that OFR was used as the organic ligands to construct a new hafnium based catalyst (Hf-OFR) for Meerwein-Ponndorf-Verley (MPV) reactions of biomass-derived platforms. The acidic groups in OFR were used to coordinate with Hf4+, and the carbon skeleton structures in OFR were used to form the spatial network structures of the Hf-OFR catalyst. The results showed that the synthesized Hf-OFR catalyst could catalyze the MPV reduction of various carbonyl compounds under relatively mild reaction conditions, with high conversions and yields. Besides, the Hf-OFR catalyst could be recycled at least 5 times with excellent stability in activity and structures. The prepared Hf-OFR catalyst possesses the advantages of high efficiency, a simple preparation process, and low cost in ligands. The proposed strategy of constructing catalysts using OFR may provide new routes for both valuable utilization of the OFR solid waste in the fermentation industry and the construction of efficient catalysts for biomass conversion.
Chen, Yuxin,Yao, Xuefeng,Wang, Xiaolu,Zhang, Xuefeng,Zhou, Huacong,He, Runxia,Liu, Quansheng
p. 13970 - 13979
(2021/04/22)

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)

Half-sandwich ruthenium(II) complexes containing 4-substituted aniline derivatives: structural characterizations and catalytic properties in transfer hydrogenation of ketones
Four half-sandwich Ru(II) complexes (1)–(4) with the general formulae [Ru(η6-p-cymene)(L)Cl2] were synthesized by the reaction of one equivalent of the Ru(II) p-cymene dimer with two equivalents of a p-substituted aniline derivative L (where L is p-methyl, p-isopropyl, p-methoxy, or p-hydroxy aniline). The structures of complexes (2)–(4) were determined by single-crystal X-ray diffraction studies. The structural analysis revealed piano-stool geometry at the Ru(II) ions which are coordinated to the η6-p-cymene, two chloride anions and the amine group of the aniline ligand. In the structure of (2)–(4), the coordinated chloride ions make intermolecular hydrogen bonding with the –NH2 group of an adjacent molecules (NH–Cl) resulting in hydrogen bond networks. The catalytic activities of the complexes in transfer hydrogenation of acetophenone were studied. Complex [Ru(η6-p-cymene)(p-methylaniline)Cl2] (1) showed the best catalytic performance in the transfer hydrogenation of acetophenone. The presence and positions of methyl and bromide groups on the acetophenone have an impact on the catalytic activity in transfer hydrogenation properties of the complex (1). Moreover, catalytic activity of the complex (1) is significantly higher in the transfers hydrogenation of cyclohexanone than 2-hexanone.
Sad?k, Mean,Karabork, Muharrem,Sahin, Irfan,Kose, Muhammet
p. 457 - 464
(2021/05/21)

Hydrosilylation of Carbonyl Compounds Catalyzed by a Nickel Complex Bearing a PBP Ligand
The efficient catalytic hydrosilylation of ketones and aldehydes has been investigated using a nickel pincer hydride complex supported by a diphosphino-boryl ligand (PBP). It was found that the presence of the boryl group within the skeleton of the ligand has a beneficial effect on the catalytic activities observed for ketones compared to related pincer systems. The analysis of the reaction mechanism allows for the synthesis and characterization of a nickel alkoxide derivative by insertion of the carbonyl moiety into the Ni?H bond. Combined experimental and theoretical analysis (DFT) support a reaction mechanism that involves the initial formation of an alkoxide complex followed by reaction with the silane to release the corresponding silyl ether and regenerate the catalyst.
Antonio Fernández, José,Manuel García, Juan,Ríos, Pablo,Rodríguez, Amor
p. 2993 - 2998
(2021/07/10)

Hydrogen-Catalyzed Acid Transformation for the Hydration of Alkenes and Epoxy Alkanes over Co-N Frustrated Lewis Pair Surfaces
Hydrogen (H2) is widely used as a reductant for many hydrogenation reactions; however, it has not been recognized as a catalyst for the acid transformation of active sites on solid surface. Here, we report the H2-promoted hydration of alkenes (such as styrenes and cyclic alkenes) and epoxy alkanes over single-atom Co-dispersed nitrogen-doped carbon (Co-NC) via a transformation mechanism of acid-base sites. Specifically, the specific catalytic activity and selectivity of Co-NC are superior to those of classical solid acids (acidic zeolites and resins) per micromole of acid, whereas the hydration catalysis does not take place under a nitrogen atmosphere. Detailed investigations indicate that H2 can be heterolyzed on the Co-N bond to form Hδ-Co-N-Hδ+ and then be converted into OHδ-Co-N-Hδ+ accompanied by H2 generation via a H2O-mediated path, which significantly reduces the activation energy for hydration reactions. This work not only provides a novel catalytic method for hydration reactions but also removes the conceptual barriers between hydrogenation and acid catalysis.
Deng, Qiang,Deng, Shuguang,Gao, Ruijie,Li, Xiang,Tsang, Shik Chi Edman,Wang, Jun,Zeng, Zheling,Zou, Ji-Jun
p. 21294 - 21301
(2021/12/17)

Primary Alcohols via Nickel Pentacarboxycyclopentadienyl Diamide Catalyzed Hydrosilylation of Terminal Epoxides
The efficient and regioselective hydrosilylation of epoxides co-catalyzed by a pentacarboxycyclopentadienyl (PCCP) diamide nickel complex and Lewis acid is reported. This method allows for the reductive opening of terminal, monosubstituted epoxides to form unbranched, primary alcohols. A range of substrates including both terminal and nonterminal epoxides are shown to work, and a mechanistic rationale is provided. This work represents the first use of a PCCP derivative as a ligand for transition-metal catalysis.
Lambert, Tristan H.,Steiniger, Keri A.
supporting information
p. 8013 - 8017
(2021/10/25)

Reaction of Diisobutylaluminum Borohydride, a Binary Hydride, with Selected Organic Compounds Containing Representative Functional Groups
The binary hydride, diisobutylaluminum borohydride [(iBu)2AlBH4], synthesized from diisobutylaluminum hydride (DIBAL) and borane dimethyl sulfide (BMS) has shown great potential in reducing a variety of organic functional groups. This unique binary hydride, (iBu)2AlBH4, is readily synthesized, versatile, and simple to use. Aldehydes, ketones, esters, and epoxides are reduced very fast to the corresponding alcohols in essentially quantitative yields. This binary hydride can reduce tertiary amides rapidly to the corresponding amines at 25 °C in an efficient manner. Furthermore, nitriles are converted into the corresponding amines in essentially quantitative yields. These reactions occur under ambient conditions and are completed in an hour or less. The reduction products are isolated through a simple acid-base extraction and without the use of column chromatography. Further investigation showed that (iBu)2AlBH4 has the potential to be a selective hydride donor as shown through a series of competitive reactions. Similarities and differences between (iBu)2AlBH4, DIBAL, and BMS are discussed.
Amberchan, Gabriella,Snelling, Rachel A.,Moya, Enrique,Landi, Madison,Lutz, Kyle,Gatihi, Roxanne,Singaram, Bakthan
supporting information
p. 6207 - 6227
(2021/05/06)

Ni-Al/CoOx-catalyzed hydrodeoxygenation of 5-hydroxymethylfurfural into 2,5-dimethylfuran at low temperatures without external hydrogen
Catalytic hydrodeoxygenation of 5-hydroxymethylfurfural into 2,5-dimethylfuran has received great interest in recent years. In this work, a ternary Ni-Al/CoOx-1 catalyst was fabricated, which provided 96% yield of DMF from in situ hydrodeoxygenation of HMF under mild reaction conditions. XRD, TEM and TPR revealed that the addition of Al to the Ni-Co bimetallic system could make the structure more stable and improve the dispersion of Ni and Co species. XPS, CO-DRIFTS and EPR verified that an enhanced electron transfer from Co species to Ni occurred on Ni-Al/CoOx-1. Reaction mechanism studies unraveled that the Al addition results in promoting in situ H2 production from 2-propanol and accelerating the aldehyde group hydrogenation to a hydroxymethyl group and the subsequent hydrogenolysis into a methyl group, due to the formation of a charge separated metal-couple-site (Niδ-Coδ+) and stronger Lewis acid sites in Ni-Al/CoOx-1. In addition, this ternary Ni-Al/CoOx-1 catalyst exhibits superior recyclability without significant loss of activity for 7 cycles.
An, Yadan,Bai, Guoyi,Bian, Gang,Li, Tianming,Niu, Libo,Xia, Zhanghui
p. 7763 - 7772
(2021/10/12)

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)

Direct Visualization of Substitutional Li Doping in Supported Pt Nanoparticles and Their Ultra-selective Catalytic Hydrogenation Performance
It has only recently been established that doping light elements (lithium, boron, and carbon) into supported transition metals can fill interstitial sites, which can be observed by the expanded unit cell. As an example, interstitial lithium (intLi) can block H filling octahedral interstices of palladium metal lattice, which improves partial hydrogenation of alkynes to alkenes under hydrogen. In contrast, herein, we report intLi is not found in the case of Pt/C. Instead, we observe for the first time a direct ‘substitution’ of Pt with substitutional lithium (subLi) in alternating atomic columns using scanning transmission electron microscopy-annular dark field (STEM-ADF). This ordered substitutional doping results in a contraction of the unit cell as shown by high-quality synchrotron X-ray diffraction (SXRD). The electron donation of d-band of Pt without higher orbital hybridizations by subLi offers an alternative way for ultra-selectivity in catalytic hydrogenation of carbonyl compounds by suppressing the facile CO bond breakage that would form alcohols.
Chen, Tianyi,Foo, Christopher,Zheng, Jianwei J. W.,Fang, Huihuang,Nellist, Peter,Tsang, Shik Chi Edman
supporting information
p. 12041 - 12046
(2021/07/14)

Facile gas-phase hydrodeoxygenation of 2,5-dimethylfuran over bifunctional metal-acid catalyst Pt-Cs2.5H0.5PW12O40
2,5-Dimethylfuran is deoxygenated to n-hexane with 100% yield on a bifunctional Pt/C-Cs2.5H0.5PW12O40 catalyst under very mild conditions (90 °C, 1 bar H2) in a one-step gas-phase process. A proposed mechanism includes a sequence of hydrogenolysis, hydrogenation and dehydration steps occurring on Pt and proton sites of the bifunctional catalyst.
Althikrallah, Hanan,Kozhevnikova, Elena F.,Kozhevnikov, Ivan V.
supporting information
p. 227 - 230
(2021/01/14)

Multifunctional NiCoTi?Catalyst Derived from Layered Double Hydroxides for Selective Hydrogenation of 5-Hydroxymethylfurfural to 2,5-Dimethylfuran
Multifunctional NiCoTi metal oxide catalysts (denoted herein as NiCoTi-x, where x is the molar ratio Ni + Co:Ti) were successfully prepared by thermal treatment of NiCoTi layered double hydroxide (LDH) precursors. The NiCoTi-x catalysts were then applied to the hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF). The Ni:Co:Ti molar ratio in the catalysts was found to strongly influence both catalyst activity and product selectivity. A NiCoTi-8 catalyst, containing Ni, Co and Ti in a 4:4:1 molar ratio (i.e. Ni + Co/Ti = 8), displayed outstanding performance for HMF hydrogenation at 200?°C and 1.5?MPa, evidenced by a 90.7% HMF conversion and 95.8% selectivity to DMF. Graphic Abstract: A ternary metal oxide catalyst derived from a layered double hydroxide was proposed for the efficient and selective hydrogenation of 5-hydroxymethylfurfural to 2,5-methylfuran.[Figure not available: see fulltext.]
Ma, Ning,Song, Yong,Han, Feng,Waterhouse, Geoffrey I. N.,Li, Yan,Ai, Shiyun
p. 517 - 525
(2020/07/28)

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)

The construction of novel and efficient hafnium catalysts using naturally existing tannic acid for Meerwein-Ponndorf-Verley reduction
The conversion of carbonyl compounds into alcohols or their derivatives via the catalytic transfer hydrogenation (CTH) process known as Meerwein-Ponndorf-Verley reduction is an important reaction in the reaction chain involved in biomass transformation. The rational design of efficient catalysts using natural and renewable materials is critical for decreasing the catalyst cost and for the sustainable supply of raw materials during catalyst preparation. In this study, a novel hafnium-based catalyst was constructed using naturally existing tannic acid as the ligand. The prepared hafnium-tannic acid (Hf-TA) catalyst was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetry (TG). Hf-TA was applied in the conversion of furfuraldehyde (FD) to furfuryl alcohol (FA) using isopropanol (2-PrOH) as both the reaction solvent and the hydrogen source. Both preparation conditions and the effects of the reaction parameters on the performance of the catalyst were studied. Under the relatively mild reaction conditions of 70 °C and 3 h, FD (1 mmol) could be converted into FA with a high yield of 99.0%. In addition, the Hf-TA catalyst could be reused at least ten times without a notable decrease in activity and selectivity, indicating its excellent stability. It was proved that Hf-TA could also catalyze the conversion of various carbonyl compounds with different structures. The high efficiency, natural occurrence of tannic acid, and facile preparation process make Hf-TA a potential catalyst for applications in the biomass conversion field.
Deng, Lijuan,Hao, Jianxiu,He, Runxia,Li, Na,Liu, Quansheng,Wang, Xiaolu,Zhao, Hongye,Zhi, Keduan,Zhou, Huacong
p. 6944 - 6952
(2020/03/03)

A novel hafnium-graphite oxide catalyst for the Meerwein-Ponndorf-Verley reaction and the activation effect of the solvent
Construction and application of novel hydrogenation catalysts is important for the conversion of carbonyl or aldehyde compounds into alcohols in the field of biomass utilization. In this work, a novel, efficient, and easily prepared hafnium-graphite oxide (Hf-GO) catalyst was constructed via the coordination between Hf4+ and the carboxylic groups in GO. The catalyst was applied into the hydrogenation of biomass derived carbonyl compounds via the Meerwein-Ponndorf-Verley (MPV) reaction. The catalyst gave high efficiency under mild conditions. An interesting phenomenon was found whereby the activity of the catalyst increased gradually in the initial stage during reaction. The solvent, isopropanol, was proved to have an activation effect on the catalyst, and the activation effect varied with different alcohols and temperatures. Further characterizations showed that isopropanol played the activation effect via replacing the residual solvent (DMF) in micro- and mesopores during the preparation process, which was hard to be completely removed by common drying process.
Li, Xiaomin,Du, Zhengjiang,Wu, Yi,Zhen, Yadong,Shao, Rixin,Li, Bingqi,Chen, Chengmeng,Liu, Quansheng,Zhou, Huacong
p. 9985 - 9995
(2020/03/26)

Transfer hydrogenation of aldehydes and ketones catalyzed using an aminophosphinite POCNHpincer complex of Ni(ii)
The aminophosphinite pincer complex (POCNH)NiBr was found to effectively catalyze the transfer hydrogenation of aldehydes and ketones with 2-propanol and KOtBu as a base, presenting a rare example of bifunctional nickel transfer hydrogenation catalysts. The transfer hydrogenation of aldehydes and ketones was found to be selective, tolerating a wide range of other functional groups, including those prone to reduction, such as esters, amides, alkenes, pyridines, and nitriles. The reactions were suggested to proceedviathe metal-ligand cooperative mechanism with an intermediacy of an amido (POCN)NiIIspecies.
?ztop?u, ?zgür,Hayrapetyan, Davit,Khalimon, Andrey Y.,Lyssenko, Konstantin A.,Segizbayev, Medet,Shakhman, Dinmukhamed
supporting information
p. 11950 - 11957
(2020/09/21)

Base-free transfer hydrogenation of aryl-ketones, alkyl-ketones and alkenones catalyzed by an IrIIICp* complex bearing a triazenide ligand functionalized with pyrazole
An IrIIICp* complex (2) bearing a triazenide ligand functionalized with pyrazole was synthesized and fully characterized by spectroscopic methods and the structure confirmed by X-ray diffraction studies. The catalytic activity of 2 and the control complex 3, which lacks of pyrazole in its structure, was evaluated in the reduction of aryl-ketones, alkyl-ketones, α,β-unsaturated and γ,δ-unsaturated ketones. The catalytic system, using either 2 or 3, exhibited good to excellent selectivity when tested with ketones and alkenones at 90 °C in 2-propanol as hydrogen source under base-free conditions. Reactivity of 2 in 2-propanol and NaH gave a neutral metal hydride (4) while in the absence of base gave two major cationic hydrides species (5 and 6).
Medrano-Castillo, Layla J.,Collazo-Flores, Miguel á.,Camarena-Díaz, Juan P.,Correa-Ayala, Erick,Chávez, Daniel,Grotjahn, Douglas B.,Rheingold, Arnold L.,Miranda-Soto, Valentín,Parra-Hake, Miguel
(2020/03/13)

Synthesis, structural characterization and C–H activation property of a tetra-iron(III) cluster
A non-heme tetra-iron cluster, [Fe4 III(μ-O)2(μ-OAc)6(2,2′-bpy)2(H2O)2](NO3 ?)(OH?) (1), [OAc = acetate; 2,2′-bpy = 2,2′-bipyridine] containing oxido- and acetato-bridges was synthesized and structurally characterized by different spectroscopic methods including single crystal X-ray diffraction studies. X-ray crystal structure analysis of 1 revealed that tetra-iron complex was crystallized in monoclinic system with C2/c space group. Each of the Fe centres in 1 was found to exist in octahedral geometry and interconnected by oxido- and acetato-bridges. Bond valence sum (BVS) calculation recommended the existence of iron centres in +3 oxidation state. Variable temperature magnetic measurement authenticated the dominating antiferromagnetic ordering among the iron centres in the solid state of 1. This tetra-iron cluster was also evaluated as an efficient catalytic system towards the oxidation of both linear & cyclic alkanes without production of primary C–H bond oxidation products. Oxidation of secondary C–H bonds attested the formation of both the corresponding alcohols & ketones in 27–900 TONs. The tetra-iron catalytic system with Alcohol/Ketone values 0.2–1.7 indicated the involvement of freely diffusing carbon-centered radicals rather than metal based oxidant.
Dey, Dhananjay,Patra, Moumita,Al-Hunaiti, Afnan,Yadav, Hare Ram,Al-mherat, Afrah,Arar, Sharif,Maji, Milan,Choudhury, Angshuman Roy,Biswas, Bhaskar
p. 220 - 226
(2019/01/05)

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)

Heteroditopic Ru(II)-And Ir(III)-NHC Complexes with Pendant 1,2,3-Triazole/Triazolylidene Groups: Stereoelectronic Impact on Transfer Hydrogenation of Unsaturated Compounds
Imidazol-2-ylidene (ImNHC) and 1,2,3-Traizol-5-ylidene (tzNHC) have been established as important classes of carbene ligands in homogeneous catalysis. To develop Ru(II)/Ir(III) complexes based on these ligand systems considering their electronic as well as steric profiles for hydride transfer reactions, we employed chelating ligands featuring combinations of ImNHC and triazole-N or mesoionic tzNHC donors bridged by a CH2 spacer with possible modifications at triazole backbone. In general, synthesized Ru(II) complexes were found to perform significantly better than analogous Ir(III) complexes in ketone and aldimine reduction. Among the Ru(II) complexes, electron-rich complexes 8/9 of the general formula [(p-cymene)(ImNHC-CH2-TzNHC)RuII(Cl)]BF4 with two different carbene donors (ImNHC and tzNHC) were found to perform appreciably better in ketone reduction than analogous complexes with a combination of ImNHC and triazole-N-donor ([(p-cymene)(ImNHC-CH2-Tz-N)RuII(Cl)]BF4; 4) explaining the electronic fine-Tuning of the catalytic systems. No appreciable variation in activity was observed between complexes 8 and 9 having almost similar electronic profiles. However, less bulky Ru(II) complex 9 with a triazole N-phenyl substituent is more suitable for aldimine reduction than is complex 8, having a triazole N-3,5-dimethylphenyl substituent that explains the steric influence in addition to electronic effect on the reduction process.
Illam, Praseetha Mathoor,Donthireddy,Chakrabartty, Sayantan,Rit, Arnab
supporting information
p. 2610 - 2623
(2019/07/31)

Molybdenum Oxide-Modified Iridium Catalysts for Selective Production of Renewable Oils for Jet and Diesel Fuels and Lubricants
Supported inverse metal-metal oxide catalysts have received significant research interest owing to their effective hydrodeoxygenation (HDO) activity toward biomass substrates, but the high cost of the reported catalysts poses a challenge for commercialization. We present the synthesis of a series of metal-metal oxide catalysts, Ir-MOx/SiO2 (M = Re, Mo, W, V, or Nb) and M′-MoOx/SiO2 (M = Rh, Ru, Pt, or Pd) and their HDO performance on multifuran (high carbon) substrates to produce renewable jet and diesel fuels and lubricant base oils. A MoOx-modified Ir/SiO2 catalyst with a Mo/Ir ratio of 0.13 (Ir-MoOx/SiO2) exhibits the highest product yield (78-96%) under mild reaction conditions. Controlled experiments using probe substrates reveal that furan ring hydrogenation and C-O hydrogenolysis of saturated and unsaturated furan rings occur in a sequential manner. The carbon atom adjacent to the furan or saturated furan ring of substrates or intermediate compounds undergoes slow C-C bond scission, resulting in a small fraction of lighter alkanes. Catalyst characterization suggests that Ir is reduced to a fully metallic state to dissociate hydrogen for hydrogenation. Intact MoOx, partly covering the Ir metal surface, promotes ring opening, hydrogenolysis of etheric and alcoholic C-O bonds, and hydrogenation of Ca? O bonds. This study highlights the potential of low-cost metal-metal oxide catalysts with low loading of oxophilic metals to enable cost-competitive production of bioproducts and demonstrates applicability of these catalysts on other substrates, including fatty acids, fatty esters, and lipids.
Liu, Sibao,Zheng, Weiqing,Fu, Jiayi,Alexopoulos, Konstantinos,Saha, Basudeb,Vlachos, Dionisios G.
p. 7679 - 7689
(2019/08/20)

Trifluoroacetic acid promoted hydration of styrene catalyzed by sulfonic resins: Comparison of the reactivity of styrene, n-hexene and cyclohexene
Alcohol production by olefin hydration is an important reaction in the modern intermediate chemistry. The use of trifluoroacetic acid (TFA) could be a way to increase alcohol productivity by addition of the TFA to the double bond forming the corresponding ester. The product obtained by addition is then hydrolyzed to alcohol by sulfonic resins. The study of the overall multiphase equilibrium aqueous TFA solution/olefin ester cyclohexene is carried out together with the initial rate of reaction for cyclohexene hydration. Reaction profiles and a likely reaction path is also given. The influence of the operative variable on both equilibria and initial reaction rate are studied in the range of temperature typical of the sulfonic resin as catalysts (383–413 K). The use of aqueous TFA allows fast reaction and high conversion as well as an easily separable aqueous system compared with other organic acid.
Bianchini, Edoardo,Pietrobon, Luca,Ronchin, Lucio,Tortato, Claudio,Vavasori, Andrea
p. 130 - 138
(2018/11/26)

Rh(III)Cp? and Ir(III)Cp? Complexes of 1-[(4-Methyl)phenyl]-3-[(2-methyl-4′-R)imidazol-1-yl]triazenide (R = t-Bu or H): Synthesis, Structure, and Catalytic Activity
A series of iridium and rhodium complexes have been synthesized using as ligand a triazenide monofunctionalized with an imidazole substituent. Steric hindrance at the imidazole moiety induced differences in the coordination modes as well in the catalytic behavior of complexes 4-7. Complexes 4-7 were tested in the transfer hydrogenation of acetophenone and 5-alken-2-ones. The hydrogenation of either the double bond or the carbonyl group in 5-alken-2-ones, showed to be selective in the presence of 6, 7, and 10 and has a dependence on the presence or absence of base. Control experiments point out that the imidazole moiety in the structure of complexes 4-7 speeds-up the catalysis.
Camarena-Diáz, Juan P.,Iglesias, Ana L.,Chávez, Daniel,Aguirre, Gerardo,Grotjahn, Douglas B.,Rheingold, Arnold L.,Parra-Hake, Miguel,Miranda-Soto, Valentín
p. 844 - 851
(2019/02/19)

Simple H2-free hydrogenation of unsaturated monoterpenoids catalyzed by Raney nickel
A series of monoterpenoids (citral, carvone, menthone, camphor) as well as cyclohexanone and hex-5-en-2-one were subjected to transfer hydrogenation with PriOH/Raney nickel system at 82 or 150 °C. Among monoterpenoids, citral and carvone underwent full conversion at 82 °C within 5 h.
Philippov, Alexey A.,Chibiryaev, Andrey M.,Martyanov, Oleg N.
p. 380 - 381
(2019/08/20)

Manganese N-Heterocyclic Carbene Complexes for Catalytic Reduction of Ketones with Silanes
Well-defined manganese(I) carbonyl complexes bearing bis-N-heterocyclic carbene (NHC) ligands are shown to be effective catalysts for the reduction of carbonyl groups through hydrosilylation reactions. A wide variety of ketones are selectively reduced to the corresponding alcohols by using phenylsilane, and the cheap and readily abundant polymethylhydrosiloxane (PMHS) in the presence of catalytic amounts of MnI organometallic complexes. Interestingly, α,β-unsaturated ketones and dialkyl ketones are selectively reduced. Mechanistic studies based on radical scavengers suggest the involvement of radical species in the catalytic reaction.
Pinto, Mara,Fri?es, Sofia,Franco, Federico,Lloret-Fillol, Julio,Royo, Beatriz
p. 2734 - 2740
(2018/07/24)

Carbonyl and ester C-O bond hydrosilylation using κ4-diimine nickel catalysts
The synthesis of alkylphosphine-substituted α-diimine (DI) ligands and their subsequent addition to Ni(COD)2 allowed for the preparation of (iPr2PPrDI)Ni and (tBu2PPrDI)Ni. The solid state structures of both compounds were found to feature a distorted tetrahedral geometry that is largely consistent with the reported structure of the diphenylphosphine-substituted variant, (Ph2PPr DI)Ni. To explore and optimize the synthetic utility of this catalyst class, all three compounds were screened for benzaldehyde hydrosilylation activity at 1.0 mol% loading over 3 h at 25 °C. Notably, (Ph2PPr DI)Ni was found to be the most efficient catalyst while phenyl silane was the most effective reductant. A broad scope of aldehydes and ketones were then hydrosilylated, and the silyl ether products were hydrolyzed to afford alcohols in good yield. When attempts were made to explore ester reduction, inefficient dihydrosilylation was noted for ethyl acetate and no reaction was observed for several additional substrates. However, when an equimolar solution of allyl acetate and phenyl silane was added to 1.0 mol% (Ph2PPr DI)Ni, complete ester C-O bond hydrosilylation was observed within 30 min at 25 °C to generate propylene and PhSi(OAc)3. The scope of this reaction was expanded to include six additional allyl esters, and under neat conditions, turnover frequencies of up to 990 h-1 were achieved. This activity is believed to be the highest reported for transition metal-catalyzed ester C-O bond hydrosilylation. Proposed mechanisms for (Ph2PPr DI)Ni-mediated carbonyl and allyl ester C-O bond hydrosilylation are also discussed.
Rock, Christopher L.,Groy, Thomas L.,Trovitch, Ryan J.
supporting information
p. 8807 - 8816
(2018/07/13)

Chiral C2-symmetric η6-p-cymene-Ru(II)-phosphinite complexes: Synthesis and catalytic activity in asymmetric reduction of aromatic, methyl alkyl and alkyl/aryl ketones
Chiral C2-symmetric bis(phosphinite) ligands and their binuclear ruthenium(II) complexes have been synthesized and used as catalysts in the ruthenium-catalyzed asymmetric transfer hydrogenation of aromatic, methyl alkyl and alkyl/aryl ketones using 2-propanol as both the hydrogen source and solvent in the presence of KOH. Under optimized conditions, all complexes showed high catalytic activity as catalysts in the reduction of various ketones to corresponding chiral secondary alcohols. Products were obtained with high conversions (99%) and moderate to good enantioselectivities (82% ee). Furthermore, C2-symmetric bis(phosphinite) ligands and their binuclear ruthenium(II) complexes were characterized by multinuclear NMR spectroscopy, FT-IR spectroscopy, LC/MS-MS and elemental analysis.
Karaka?, Duygu Elma,Aydemir, Murat,Durap, Feyyaz,Baysal, Ak?n
p. 430 - 439
(2017/12/06)

Applying Le Chatelier's Principle for a Highly Efficient Catalytic Transfer Hydrogenation with Ethanol as the Hydrogen Source
While isopropanol or formic acid derivatives are mainly applied as hydrogen sources in catalytic transfer hydrogenation reactions, there are only a few reports on the use of primary alcohols. In the present communication we report that ecologically benign and cheap ethanol can be applied with a ruthenium(II) that is completely stable against moisture and oxygen. Catalytic transfer hydrogenation is an equilibrium reaction. Therefore, a rapid removal of acetic aldehyde being formed as the product of ethanol oxidation is the key for high conversions. The reaction shows a broad substrate scope and allows the hydrogenation of ketones, aldehydes and imines.
Weingart, Pascal,Thiel, Werner R.
p. 4858 - 4862
(2018/10/15)

Effect of Ancillary Ligand in Cyclometalated Ru(II)-NHC-Catalyzed Transfer Hydrogenation of Unsaturated Compounds
In an effort to develop efficient Ru(II)-NHC-based catalyst considering their stereoelectronic effect for hydride-transfer reaction, we found that the ancillary NHC ligand can play a significant role in its catalytic performance. This effect is demonstrated by comparing the activity of two different types of orthometalated precatalysts of general formula [(p-cymene)(NHC)RuII(X)] (NHC = an imidazolylidene-based ImNHC, compound 2a-c, or a mesoionic triazolylidene-based tzNHC, compound 4) in transfer hydrogenation of carbonyl substrates. The electron-rich precatalyst, 2c, containing p-OMe-substituted NHC ligand performed significantly better than both unsubstituted complex 2a and p-CF3 substituted electron-poor complex 2b in ketone reduction. Whereas bulky mesoionic triazolylidene ligand containing complex 4 was found to be superior catalyst for aldehyde reduction and the precatalyst 2a is more suitable for the selective transfer hydrogenation of a wide range of aromatic aldimines to amines. To the best of our knowledge, this is the first systematic study on the effect of stereoelectronic tuning of ancillary orthometalated NHC ligand in Ru(II)-catalyzed transfer hydrogenations of various types of unsaturated compounds with broad substrate scope.
Bauri, Somnath,Donthireddy,Illam, Praseetha Mathoor,Rit, Arnab
supporting information
p. 14582 - 14593
(2018/11/25)

Synthesis of bimetallic complexes bridged by 2,6-bis(benzimidazol-2-yl) pyridine derivatives and their catalytic properties in transfer hydrogenation
A series of binuclear rhodium(i) and iridium(i) complexes with 2,6-bis(benzimidazol-2-yl) pyridine (bzimpy) derivatives were synthesized and characterized by elemental analysis and spectroscopic methods. The molecular and crystal structures of complex 3d were determined by the single crystal X-ray diffraction technique. Their monometallic analogues were prepared to compare the catalytic properties of the bimetallic complexes. To determine the catalyst properties that result in a cooperative, bimetallic enhancement of the reaction rate, the systematic variation of the intermetallic distance and the ligand donor properties of the bimetallic complexes were explored based on the transfer hydrogenation reactions of ketones.
Günnaz, Salih,G?k?e, Ayta? Gürhan,Türkmen, Hayati
p. 17317 - 17328
(2019/01/03)

Interplay between Substrate and Proton Donor Coordination in Reductions of Carbonyls by SmI2-Water Through Proton-Coupled Electron-Transfer
The reduction of a carbonyl by SmI2-water is the first step in a range of reactions of synthetic importance. Although the reduction is often proposed to proceed through an initial stepwise electron-transfer-proton-transfer (ET-PT), recent work has shown that carbonyls and related functional groups are likely reduced though proton-coupled electron-transfer (PCET). In the present work, the reduction of an activated ester, aldehyde, a linear and cyclic ketone, and related sterically demanding carbonyls by SmI2-H2O was examined through a series of mechanistic experiments. Kinetic studies demonstrate that all substrates exhibit significant increases in the rate of reduction by SmI2 as [H2O] is increased. Under identical conditions, ketones and an aldehyde containing a methyl adjacent to the carbonyl are reduced slower than an unsubstituted variant by an order of magnitude, demonstrating the importance of substrate coordination. In the case of unactivated substrates, rates of reduction show excellent correlation with the calculated bond dissociation free energy of the O-H bond of the intermediate ketyl and the calculated free energy of intermediate ketyl radical anions derived from unhindered substrates: findings consistent with concerted PCET. Activated esters derived from methylbenzoate are likely reduced through stepwise or asynchronous PCET. Overall, this work demonstrates that the combination of the coordination of substrate and water to Sm(II) provides a configuration uniquely suited to a coupled electron- and proton-transfer process.
Chciuk, Tesia V.,Anderson, William R.,Flowers, Robert A.
supporting information
p. 15342 - 15352
(2018/11/30)

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)

Interfacial CoOx Layers on TiO2 as an Efficient Catalyst for Solvent-Free Aerobic Oxidation of Hydrocarbons
Construction of efficient interfaces to improve the performance of supported metal catalysts is a challenging but effective technique. A newly synthesized catalyst with layered cobalt oxide on the surface of titania (layer-CoOx/TiO2) is highly selective towards the aerobic oxidation of C?H bonds in a series of hydrocarbons under sustainable conditions. The layer-CoOx/TiO2 easily outperforms the state-of-the-art noble metal catalysts and homogeneous cobalt salts used in industry. In-depth structural and functional characterization reveal that the layer-CoOx/TiO2 readily reacts with O2 for the adsorption and activation of C?H bonds. The layered structure of CoOx can maximize the interfacial effect of CoOx/TiO2 leading to a good performance for the oxidation of C?H bonds.
Wang, Hai,Wang, Liang,Zhang, Jian,Wang, Chengtao,Liu, Ziyu,Gao, Xinhua,Meng, Xiangju,Yoo, Seung Jo,Kim, Jin-Gyu,Zhang, Wei,Xiao, Feng-Shou
p. 3965 - 3974
(2018/10/31)

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)

CATALYST FOR ONE CARBON-REDUCTION REACTION, AND METHOD FOR PRODUCING ONE CARBON-REDUCTION COMPOUND USING THE SAME
PROBLEM TO BE SOLVED: To provide a method for producing selectively a one carbon-reduction compound, using a compound having a primary hydroxy group, a carboxyl group, or an alkoxycarbonyl group, or a lactone compound, as a substrate. SOLUTION: A method of obtaining a one carbon-reduction compound includes the reaction of a compound as a substrate represented by formula (1-1) or (1-2) or (1-3) with hydrogen in the presence of a catalyst in which a metal selected from Ru, Rh, Pd, Ir, and Pt is supported on a support selected from CeO2, hydroxyapatite, ZrO2, TiO2, hydrotalcite, SiO2, MgO, and Al2O3 (R1-R3 independently represent H, a substituted/unsubstituted monovalent hydrocarbon group, or a monovalent group in which two or more hydrocarbon groups are bound together through a linking group; R1-R3 may form a ring with adjacent carbon; L is a substituted/unsubstituted divalent hydrocarbon group or the like; and n is an integer of 0 or greater). SELECTED DRAWING: None COPYRIGHT: (C)2018,JPOandINPIT
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Paragraph 0060; 0070; 0071

(2018/07/28)

Biocatalytic Racemization Employing TeSADH: Substrate Scope and Organic Solvent Compatibility for Dynamic Kinetic Resolution
Racemization in combination with a kinetic resolution is the base for a dynamic kinetic resolution (DKR). Biocatalytic racemization was successfully performed for a broad scope of sec-alcohols by employing a single alcohol dehydrogenase (ADH) variant from Thermoanaerobacter pseudoethanolicus (formerly T. ethanolicus; TeSADH W110A I86A C295A). The catalyst employed as a lyophilized whole cell preparation or cell free extract, which tolerated various non-water miscible organic solvents under micro-aqueous or two-phase conditions, whereby cyclohexane and n-hexane suited best. Various concepts for combining the enzymatic racemization with an enzymatic kinetic resolution to achieve overall a bis-enzymatic DKR were evaluated. A proof of concept showed a successful DKR with racemization in aqueous phase combined with acylation in the organic phase.
Pop?oński, Jaros?aw,Reiter, Tamara,Kroutil, Wolfgang
p. 763 - 768
(2018/02/27)

Ruthenium NNN complexes with a 2-hydroxypyridylmethylene fragment for transfer hydrogenation of ketones
Four NNN tridentate ligands L1–L4 containing 2-methoxypyridylmethene or 2-hydroxypyridylmethene fragment were synthesized and introduced to ruthenium centers. When (HOC5H3NCH2C5H3NC5H7N2) (L2) and (HOC5H3NCH2C5H3NC6H6N3) (L4) reacted with RuCl2(PPh3)3, two ruthenium chloride products Ru(L2)(PPh3)Cl2 (1) and Ru(L4)(PPh3)Cl2 (2) were isolated, respectively. Reactions of (MeOC5H3NCH2C5H3NC5H7N2) (L1) and (MeOC5H3NCH2C5H3NC6H6N3) (L3) with RuCl2(PPh3)3 in the presence of NH4PF6 generated two dicationic complexes [Ru(L1)2][PF6]2 (3) and [Ru(L3)2][PF6]2 (4), respectively. Complex 1 reacted with CO to afford product [Ru(L2)(PPh3)(CO)Cl][Cl]. The catalytic activity for transfer hydrogenation of ketones was investigated. Complex 1 showed the highest activity, with a turnover frequency value of 1.44?×?103?h?1 for acetophenone, while complexes 3 and 4 were not active.
Shi, Jing,Shang, Shu,Hu, Bowen,Chen, Dafa
(2017/11/09)

AN ECO-FRIENDLY PROCESS FOR HYDROGENATION OR/AND HYDRODEOXYGENATION OF ORGANIC COMPOUND USING HYDROUS RUTHENIUM OXIDE CATALYST
The invention discloses aneco-friendly process for hydrogenation (alkenealkene, carbonyl compound and aromatic) and hydrodeoxygenation (methoxy phenols) of organic compound using hydrous ruthenium oxide (HRO) and its supported form as a recyclable heterogeneous catalyst in aqueous medium with good yield of desired compounds (70-100%) under mild reaction conditions. The invention also discloses hydrogenation of organic compound such as alkene, carbonyl compound and substituted aromatic and also for the processes that involve hydrodeoxygenation, for example, lignin derived aromatic (methoxy phenols).
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Page/Page column 12; 18

(2017/08/01)

Mechanistic Studies on Ruthenium(II)-Catalyzed Base-Free Transfer Hydrogenation Triggered by Roll-Over Cyclometalation
The synthesis of 2-substituted pyridine–pyrimidine ligands and their complexation with arene ruthenium(II) chloride moieties is reported. Depending on the electronic and steric influences of the ligand, the catalysts undergo CH activation by roll-over cyclometalation. This process opens up the route to the catalytic transfer hydrogenation of ketones with isopropanol as the hydrogen source under base-free and mild conditions. Barriers related to the roll-over cyclometalation process can be determined experimentally by collision-induced dissociation ESI mass spectrometry. They are supported by DFT calculations and allow the classification of the ligands according to their electronic and steric properties, which is also in accordance with critical bond parameters derived from X-ray structure data. DFT calculations furthermore reveal that the formation of a ruthenium(II) hydrido species is plausible through β-hydride elimination from isopropanol.
Kerner, Christian,Lang, Johannes,Gaffga, Maximilian,Menges, Fabian S.,Sun, Yu,Niedner-Schatteburg, Gereon,Thiel, Werner R.
p. 212 - 224
(2017/03/07)

Direct use of humic acid mixtures to construct efficient Zr-containing catalysts for Meerwein-Ponndorf-Verley reactions
With the increasing demands for energy and carbon resources, exploration of novel utilization approaches of fossil resources and promotion of the conversion of sustainable resources become critical issues facing human society. In this study, we used humic acids (HAs), which are important derivatives from the low-rank coal, and the transition metal zirconium (Zr) to construct novel Zr-containing catalysts (Zr-HAs) for Meerwein-Ponndorf-Verley (MPV) reactions of biomass-derived platforms. Both commercial HAs and HAs extracted directly from lignite without any purification were used as raw materials to prepare the catalysts. The results showed that Zr-HAs catalysts were highly efficient for the conversion of furfural, with a high furfuryl alcohol yield of up to 97%, and also effective for the conversion of other carbonyl compounds with different structures under mild conditions. This novel strategy to construct catalysts using HAs as raw materials may be beneficial for both value-added utilization of low-rank coal and the conversion of biomass resources.
Sha, Yufei,Xiao, Zhenhuan,Zhou, Huacong,Yang, Keli,Song, Yinmin,Li, Na,He, Runxia,Zhi, Keduan,Liu, Quansheng
p. 4829 - 4837
(2017/10/19)

Cp2TiCl2-catalyzed cycloboration of α-olefins with PhBCl2in the synthesis of 2-alkyl(aryl,benzyl)-1-phenylboriranes
A one-pot method for the synthesis of 2-alkyl(aryl, benzyl)-1-phenylboriranes has been developed via the reaction of α-olefins with PhBCl2in the presence of Cp2TiCl2as the catalyst. The method implies the formation of boriranes as the result of transmetalation of titanacyclopropane intermediates generated in the reaction of α-olefins with Cp2TiCl2. Individual 1-phenyl-2-substituted boriranes were isolated and their structures confirmed by NMR spectral methods.
Khusainova, Liliya I.,Khafizova, Leila O.,Tyumkina, Tatyana V.,Ryazanov, Kirill S.,Dzhemilev, Usein M.
p. 12 - 17
(2017/02/05)

Failure and Redemption of Statistical and Nonstatistical Rate Theories in the Hydroboration of Alkenes
Our previous work found that canonical forms of transition state theory incorrectly predict the regioselectivity of the hydroboration of propene with BH3 in solution. In response, it has been suggested that alternative statistical and nonstatistical rate theories can adequately account for the selectivity. This paper uses a combination of experimental and theoretical studies to critically evaluate the ability of these rate theories, as well as dynamic trajectories and newly developed localized statistical models, to predict quantitative selectivities and qualitative trends in hydroborations on a broader scale. The hydroboration of a series of terminally substituted alkenes with BH3 was examined experimentally, and a classically unexpected trend is that the selectivity increases as the alkyl chain is lengthened far from the reactive centers. Conventional and variational transition state theories can predict neither the selectivities nor the trends. The canonical competitive nonstatistical model makes somewhat better predictions for some alkenes but fails to predict trends, and it performs poorly with an alkene chosen to test a specific prediction of the model. Added nonstatistical corrections to this model make the predictions worse. Parametrized Rice-Ramsperger-Kassel-Marcus (RRKM)-master equation calculations correctly predict the direction of the trend in selectivity versus alkene size but overpredict its magnitude, and the selectivity with large alkenes remains unpredictable with any parametrization. Trajectory studies in explicit solvent can predict selectivities without parametrization but are impractical for predicting small changes in selectivity. From a lifetime and energy analysis of the trajectories, "localized RRKM-ME" and "competitive localized noncanonical" rate models are suggested as steps toward a general model. These provide the best predictions of the experimental observations and insight into the selectivities.
Bailey, Johnathan O.,Singleton, Daniel A.
supporting information
p. 15710 - 15723
(2017/11/14)

Efficient carbon-supported heterogeneous molybdenum-dioxo catalyst for chemoselective reductive carbonyl coupling
Reductive coupling of various carbonyl compounds to the corresponding symmetric ethers with dimethylphenylsilane is reported using a carbon-supported dioxo-molybdenum catalyst. The catalyst is air- and moisture-stable and can be easily separated from the reaction mixture for recycling. In addition, the catalyst is chemoselective, thus enabling the synthesis of functionalized ethers without requiring sacrificial ligands or protecting groups.
Liu, Shengsi,Li, Jiaqi,Jurca, Titel,Stair, Peter C.,Lohr, Tracy L.,Marks, Tobin J.
p. 2165 - 2169
(2017/07/22)

Heterogeneous Ketone Hydrodeoxygenation for the Production of Fuels and Feedstocks from Biomass
In this work, we describe a simple, heterogeneous catalytic system for the hydrodeoxygenation (HDO) of 5-nonanone and 2,5-hexanedione, which we use as model compounds for more complex biomass-derived molecules. We present the stepwise reduction of ketones by using supported metal and solid acid catalysts to identify the intermediates en route to hydrocarbons. Although monoketone HDO can be achieved rapidly using moderate conditions (Ni/SiO2.Al2O3, HZSM-5, 200 °C, 1.38 MPa H2, 1 h), quantitative γ-polyketone HDO requires higher pressures and longer reaction times (Pd/Al2O3, HZSM-5, 2.76 MPa H2, 5 h), although these are more facile conditions than have been reported previously for γ-polyketone HDO. Stepwise HDO of the γ-polyketone shows the reaction pathway occurs through ring-closure to a saturated tetrahydrofuran species intermediate, which requires increased H2 pressure to ring-open and subsequently to fully HDO. This work allows for further understanding of bio-derived molecule defunctionalization mechanisms, and ultimately aids in the promotion of biomass as a feedstock for fuels and chemicals.
Jenkins, Rhodri W.,Moore, Cameron M.,Semelsberger, Troy A.,Sutton, Andrew D.
p. 2807 - 2815
(2017/07/28)