- Photochemistry of 1,2-dihydronaphthaiene oxide: Concurrent triplet and singlet processes via singlet excitation
-
The photochemistry of 1,2-dihydronaphthalene oxide (254 nm) was reexamined and indan was found to be a primary photoproduct, as well as the traditionally assumed secondary photoproduct. Quenching studies demonstrated that indan, as a primary photoproduct, is derived from a triplet pathway, competing with a singlet route, back to the ground state surface. CASSCF calculations strongly suggest that the triplet pathway consists of a dissociation of the oxirane moiety to give a triplet carbene and aldehyde, which via hydrogen abstraction-decarbonylation-ISC recloses to give indan. Conical intersections corresponding to the presumed 1,2-hydrogen shift and 1,2-alkyl shift to give 2-tetralone and 1-indancarbaldehyde, respectively, were located computationally.
- White, Rick C.,Arney Jr., Benny E.,White, Katherine M.
-
-
Read Online
- The Disproportionation of cis-Bicyclonona-3,7-diene Catalyzed by Fe(CO)5 and Cp2Fe2(CO)4
-
cis-Bicyclonona-3,7-diene (1) was catalytically disproportionated by the use of Fe(CO)5 and Cp2Fe2(CO)4 to bicyclonon-1(6)-ene (3) and indan (4).However, the same reaction catalyzed by the use of other metal carbonyls gave merely small amount of 3 and 4, while those using Pd- and Rh-carbons yielded only 4 and the starting material, 1, respectively.
- Kagayama, Takashi,Okabayashi, Shinji,Amaike, Yoichi,Matsukawa, Yasuo,Ishii, Yasutaka,Ogawa, Masaya
-
-
Read Online
- Synthesis and Properties of 1,2-Dimethylene-3,5-cycloheptadiene
-
The regioselective synthesis of dimethyl 1,3,5-cycloheptariene-1,2-dicarboxylate (4) was achieved by a ring expansion method, starting from dimethyl 1,3-cyclohexadiene-2,3-dicarboxylate (5).The title compound 3 was obtained as an air-sensitive oil by zinc-copper reduction of 1,2-bis(bromomethyl)cyclohepta-1,3,5-triene (10) to which the diester 4 was transformed.
- Oda, Mitsunori,Kuroda, Shigeyasu,Shimao, Ichiro,Morita, Noboru,Asao, Toyonobu
-
-
Read Online
- Generation and Transformation of the Propellane Skeleton by Thermal Rearrangements
-
In a sequence of unexpected thermal rearrangements the strained monocyclic alkyne 4 is transformed into the tricyclic system 5 which yields in a flash vacuum pyrolysis again a monocyclic compound 10.
- Kraemer, Guido,Kolshorn, Heinz,Meier, Herbert
-
-
Read Online
- Reduction method of electronic salt reaction liquid and unsaturated aromatic hydrocarbon compound
-
To the reduction method, tetrahydrofuran is used as a solvent and an electron trapping agent, metal lithium is used as a reducing agent, tertiary butanol is used as a reducing agent, and the unsaturated aromatic hydrocarbon compound is reduced under -10 - 0 °C conditions. The raw material tetrahydrofuran is used in the invention. Metal lithium and tert-butyl alcohol are all conventional chemical products, and are simple and easy to obtain. After the reaction is finished, excess lithium and solvent are recovered, and directly used to realize low cost, low pollution and high yield.
- -
-
Paragraph 0084-0087
(2021/11/10)
-
- Remarkable catalytic activity of polymeric membranes containing gel-trapped palladium nanoparticles for hydrogenation reactions
-
Polymeric flat-sheet membranes and hollow fibers were prepared via UV photo-initiated polymerization of acrylic acid at the surface of commercial polyether sulfones (PES) membranes. These polymeric materials permitted to immobilize efficiently palladium nanoparticles (PdNP), which exhibited a mean diameter in the range of 4?6 nm. These materials were synthesized by chemical reduction of Pd(II) precursors in the presence of the corresponding support. We successfully applied the as-prepared catalytic materials in hydrogenation reactions under continuous flow conditions. Flat sheet membranes were more active than hollow fibers due to the flow configuration and defavorable operating conditions. Actually, various functional groups (i.e. C[dbnd]C, C[tbnd]C and NO2) were reduced in flow-through configuration, under mild conditions (between 1.4 and 2.2 bar H2 at 60 °C, using 3.2 mol% of Pd loading), archiving high conversions in short reaction times (12?24 s).
- López-Viveros, Melissa,Favier, Isabelle,Gómez, Montserrat,Lahitte, Jean-Fran?ois,Remigy, Jean-Christophe
-
p. 263 - 269
(2020/05/13)
-
- Boosting homogeneous chemoselective hydrogenation of olefins mediated by a bis(silylenyl)terphenyl-nickel(0) pre-catalyst
-
The isolable chelating bis(N-heterocyclic silylenyl)-substituted terphenyl ligand [SiII(Terp)SiII] as well as its bis(phosphine) analogue [PIII(Terp)PIII] have been synthesised and fully characterised. Their reaction with Ni(cod)2(cod = cycloocta-1,5-diene) affords the corresponding 16 VE nickel(0) complexes with an intramolecularη2-arene coordination of Ni, [E(Terp)E]Ni(η2-arene) (E = PIII, SiII; arene = phenylene spacer). Due to a strong cooperativity of the Si and Ni sites in H2activation and H atom transfer, [SiII(Terp)SiII]Ni(η2-arene) mediates very effectively and chemoselectively the homogeneously catalysed hydrogenation of olefins bearing functional groups at 1 bar H2pressure and room temperature; in contrast, the bis(phosphine) analogous complex shows only poor activity. Catalytic and stoichiometric experiments revealed the important role of the η2-coordination of the Ni(0) site by the intramolecular phenylene with respect to the hydrogenation activity of [SiII(Terp)SiII]Ni(η2-arene). The mechanism has been established by kinetic measurements, including kinetic isotope effect (KIE) and Hammet-plot correlation. With this system, the currently highest performance of a homogeneous nickel-based hydrogenation catalyst of olefins (TON = 9800, TOF = 6800 h?1) could be realised.
- Lücke, Marcel-Philip,Yao, Shenglai,Driess, Matthias
-
p. 2909 - 2915
(2021/03/14)
-
- Synthesis of renewable alkylated naphthalenes with benzaldehyde and angelica lactone
-
Herein, we report a new route for the synthesis of renewable alkylated naphthalenes (ANs) with benzaldehyde and angelica lactone, two platform compounds that can be derived from lignocellulose.
- Cong, Yu,Li, Guangyi,Li, Ning,Wang, Aiqin,Wang, Ran,Wang, Xiaodong,Xu, Jilei,Zhang, Tao
-
supporting information
p. 5474 - 5480
(2021/08/16)
-
- Metal-Free Heterogeneous Semiconductor for Visible-Light Photocatalytic Decarboxylation of Carboxylic Acids
-
A suitable protocol for the photocatalytic decarboxylation of carboxylic acids was developed with metal-free ceramic boron carbon nitrides (BCN). With visible light irradiation, BCN oxidize carboxylic acids to give carbon-centered radicals, which were trapped by hydrogen atom donors or employed in the construction of the carbon-carbon bond. In this system, both (hetero)aromatic and aliphatic acids proceed the decarboxylation smoothly, and C-H, C-D, and C-C bonds are formed in moderate to high yields (35 examples, yield up to 93%). Control experiments support a radical process, and isotopic experiments show that methanol is employed as the hydrogen atom donor. Recycle tests and gram-scale reaction elucidate the practicability of the heterogeneous ceramic BCN photoredox system. It provides an alternative to homogeneous catalysts in the valuable carbon radical intermediates formation. Moreover, the metal-free system is also applicable to late-stage functionalization of anti-inflammatory drugs, such as naproxen and ibuprofen, which enrich the chemical toolbox.
- Shi, Jiale,Yuan, Tao,Zheng, Meifang,Wang, Xinchen
-
p. 3040 - 3047
(2021/03/09)
-
- N-Atom Deletion in Nitrogen Heterocycles
-
Excising the nitrogen in secondary amines, and coupling the two residual fragments is a skeletal editing strategy that can be used to construct molecules with new skeletons, but which has been largely unexplored. Here we report a versatile method of N-atom excision from N-heterocycles. The process uses readily available N-heterocycles as substrates, and proceeds by N-sulfonylazidonation followed by the rearrangement of sulfamoyl azide intermediates, providing various cyclic products. Examples are provided of deletion of nitrogen from natural products, synthesis of chiral O-heterocycles from commercially available chiral β-amino alcohols, formal inert C?H functionalization through a sequence of N-directed C?H functionalization and N-atom deletion reactions in which the N-atom can serve as a traceless directing group.
- Cai, Wangshui,Guo, Ting,Li, Guigen,Lu, Hongjian,Qin, Haitao,Wang, Shuang
-
p. 20678 - 20683
(2021/08/25)
-
- Mild olefin formationviabio-inspired vitamin B12photocatalysis
-
Dehydrohalogenation, or elimination of hydrogen-halide equivalents, remains one of the simplest methods for the installation of the biologically-important olefin functionality. However, this transformation often requires harsh, strongly-basic conditions, rare noble metals, or both, limiting its applicability in the synthesis of complex molecules. Nature has pursued a complementary approach in the novel vitamin B12-dependent photoreceptor CarH, where photolysis of a cobalt-carbon bond leads to selective olefin formation under mild, physiologically-relevant conditions. Herein we report a light-driven B12-based catalytic system that leverages this reactivity to convert alkyl electrophiles to olefins under incredibly mild conditions using only earth abundant elements. Further, this process exhibits a high level of regioselectivity, producing terminal olefins in moderate to excellent yield and exceptional selectivity. Finally, we are able to access a hitherto-unknown transformation, remote elimination, using two cobalt catalysts in tandem to produce subterminal olefins with excellent regioselectivity. Together, we show vitamin B12to be a powerful platform for developing mild olefin-forming reactions.
- Bam, Radha,Pollatos, Alexandros S.,Moser, Austin J.,West, Julian G.
-
p. 1736 - 1744
(2021/02/22)
-
- Photocatalytic transfer hydrogenolysis of aromatic ketones using alcohols
-
A mild method of photocatalytic deoxygenation of aromatic ketones to alkyl arenes was developed, which utilized alcohols as green hydrogen donors. No hydrogen evolution during this transformation suggested a mechanism of direct hydrogen transfer from alcohols. Control experiments with additives indicated the role of acid in transfer hydrogenolysis, and catalyst characterization confirmed a larger number of Lewis acidic sites on the optimal Pd/TiO2 photocatalyst. Hence, a combination of hydrogen transfer sites and acidic sites may be responsible for efficient deoxygenation without additives. The photocatalyst showed reusability and achieved selective reduction in a variety of aromatic ketones.
- Gao, Zhuyan,Han, Jianyu,Hong, Feng,Lei, Lijun,Li, Hongji,Liu, Huifang,Luo, Nengchao,Wang, Feng
-
p. 3802 - 3808
(2020/07/09)
-
- Tetraalkylammonium Functionalized Hydrochars as Efficient Supports for Palladium Nanocatalysts
-
With the aim of preparing bio-sourced supports with enhanced properties in catalysis, we devised an original strategy allowing the immobilization of metal nanoparticles. Thus, size-controlled hydrochars with a high degree of hydroxyl functionalities, from both neat sucrose or modified with acrylic acid (10 wt.%), were derivatized with ether linkers containing ammonium groups. These non-porous carbon-based materials were used as suitable supports for the immobilization of palladium nanoparticles. The catalytic materials were synthesized by reduction of Pd(OAc)2 to Pd(0) under H2 atmosphere in the presence of the corresponding hydrochar, and fully characterized by standard methods. Among the different hydrochar-supported palladium materials, those functionalized with tetraalkylammonium groups afforded heterogeneous catalysts, exhibiting high activity in hydrogenations of different types of substrates (alkynes, alkenes, and carbonyl and nitro derivatives). The most efficient catalyst was recycled up to ten runs without loss of catalytic behavior, in agreement with the unchanged composite materials after catalysis (Transmission Electron Microscopy (TEM) analyses) and the lack of metal leaching in the extracted organic products (no palladium detected by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES)); these systems exhibited enhanced recyclability properties as compared to commercial Pd/C catalyst.
- Duarte, Tiago A. G.,Favier, Isabelle,Pradel, Christian,Martins, Luísa M. D. R. S.,Carvalho, Ana P.,Pla, Daniel,Gómez, Montserrat
-
p. 2295 - 2303
(2020/03/23)
-
- Fine-Bubble-Slug-Flow Hydrogenation of Multiple Bonds and Phenols
-
We describe a promising method for the continuous hydrogenation of alkenes or alkynes by using a newly developed fine-bubble generator. The fine-bubble-containing slug-flow system was up to 1.4 times more efficient than a conventional slug-flow method. When applied in the hydrogenation of phenols to the corresponding cyclohexanones, the fine bubble-slug-flow method suppressed over-reduction. As this method does not require the use of excess gas, it is expected to be widely applicable in improving the efficiency of gas-mediated flow reactions.
- Iio, Takuya,Nagai, Kohei,Kozuka, Tomoki,Sammi, Akhtar Mst,Sato, Kohei,Narumi, Tetsuo,Mase, Nobuyuki
-
supporting information
p. 1919 - 1924
(2020/11/09)
-
- Photochemical Unmasking of Polyyne Rotaxanes
-
Bulky photolabile masked alkyne equivalents (MAEs) are needed for the synthesis of polyyne polyrotaxanes, as insulated molecular wires and as stabilized forms of the linear polymeric allotrope of carbon, carbyne. We have synthesized a novel MAE based on phenanthrene and compared it with an indane-based MAE. Photochemical unmasking of model compounds was studied at different wavelengths (250 and 350 nm), and key products were identified by NMR spectroscopy and X-ray crystallography. UV irradiation at 250 nm leads to unmasking of both MAEs. Irradiation of the phenanthrene system at 350 nm results in quantitative dimerization via [2 + 2] cycloaddition to form a [3]-ladderane; irradiation of this ladderane at 250 nm generates a dihydrotriphenylene, which can be oxidized easily to a triphenylene. Irradiation of the indane-based MAE at 350 nm in the presence of traces of oxygen forms an endoperoxide and a bisepoxide. Both MAEs have been incorporated into rotaxanes via copper-mediated active metal template Glaser or Cadiot-Chodkiewicz coupling. The identity of the rotaxanes was confirmed by NMR spectroscopy and mass spectrometry. The phenanthrene rotaxane decomposes during attempted photochemical unmasking, whereas photolysis of the indane rotaxane results in unmasking of the polyyne thread to form a rotaxane with a chain of 16 sp-hybridized carbon atoms. This approach opens avenues toward the synthesis of encapsulated carbon allotropes.
- Woltering, Steffen L.,Gawel, Przemyslaw,Christensen, Kirsten E.,Thompson, Amber L.,Anderson, Harry L.
-
supporting information
p. 13523 - 13532
(2020/09/02)
-
- Reductive Deamination with Hydrosilanes Catalyzed by B(C6F5)3
-
The strong boron Lewis acid tris(pentafluorophenyl)borane B(C6F5)3 is known to catalyze the dehydrogenative coupling of certain amines and hydrosilanes at elevated temperatures. At higher temperature, the dehydrogenation pathway competes with cleavage of the C?N bond and defunctionalization is obtained. This can be turned into a useful methodology for the transition-metal-free reductive deamination of a broad range of amines as well as heterocumulenes such as an isocyanate and an isothiocyanate.
- Fang, Huaquan,Oestreich, Martin
-
supporting information
p. 11394 - 11398
(2020/05/25)
-
- Method for hydrogenolysis of halides
-
The invention discloses a method for hydrogenolysis of halides. The invention discloses a preparation method of a compound represented by a formula I. The preparation method comprises the following step: in a polar aprotic solvent, zinc, H2O and a compound represented by a formula II are subjected to a reaction as shown in the specification, wherein X is halogen; Y is -CHRR or R; hydrogenin H2O exists in the form of natural abundance or non-natural abundance. According to the preparation method, halide hydrogenolysis can be simply, conveniently and efficiently achieved through a simple and mild reaction system, and good functional group compatibility and substrate universality are achieved.
- -
-
-
- Scalable Wolff-Kishner Reductions in Extreme Process Windows Using a Silicon Carbide Flow Reactor
-
A safe and scalable continuous flow strategy for Wolff-Kishner reductions that employs methanol as the solvent has been developed. The use of low-cost hydrazine as the reducing agent in combination with a caustic base provides an atom-efficient, environmentally friendly method for the deoxygenation of aldehydes and ketones to alkanes. Because of the required harsh and corrosive reaction conditions (200 °C, 50 bar), reactor materials such as stainless steel, glass, or any type of polymer have compatibility problems, rendering this process problematic on a production scale. The use of corrosion-resistant silicon carbide (SiC) as the reactor material opens up the possibility of performing Wolff-Kishner reductions on scale with a considerably improved safety profile. Methanol as the solvent significantly simplifies the workup procedure compared with the generally employed high-boiling solvents such as diethylene glycol. The continuous flow protocol was applied to a number of substrates and provided the desired products in good to high yields with space-time yields of up to 152 g L-1 h-1. In addition, a pharmaceutically valuable active pharmaceutical ingredient precursor was synthesized by employing this higherature/pressure Wolff-Kishner protocol.
- Znidar, Desiree,O'Kearney-Mcmullan, Anne,Munday, Rachel,Wiles, Charlotte,Poechlauer, Peter,Schmoelzer, Christoph,Dallinger, Doris,Kappe, C. Oliver
-
supporting information
p. 2445 - 2455
(2019/11/03)
-
- Rethinking Basic Concepts-Hydrogenation of Alkenes Catalyzed by Bench-Stable Alkyl Mn(I) Complexes
-
An efficient additive-free manganese-catalyzed hydrogenation of alkenes to alkanes with molecular hydrogen is described. This reaction is atom economic, implementing an inexpensive, earth-abundant nonprecious metal catalyst. The most efficient precatalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-alkyl bond to yield an acyl intermediate which undergoes rapid hydrogenolysis to form the active 16e Mn(I) hydride catalyst [Mn(dippe)(CO)2(H)]. A range of mono- A nd disubstituted alkenes were efficiently converted into alkanes in good to excellent yields. The hydrogenation of 1-alkenes and 1,1-disubstituted alkenes proceeds at 25 °C, while 1,2-disubstituted alkenes require a reaction temperature of 60 °C. In all cases, a catalyst loading of 2 mol % and a hydrogen pressure of 50 bar were applied. A mechanism based on DFT calculations is presented, which is supported by preliminary experimental studies.
- Weber, Stefan,St?ger, Berthold,Veiros, Luis F.,Kirchner, Karl
-
p. 9715 - 9720
(2019/10/14)
-
- Iridium-Catalyzed Alkene-Selective Transfer Hydrogenation with 1,4-Dioxane as Hydrogen Donor
-
The iridium-catalyzed transfer hydrogenation of alkenes using 1,4-dioxane as a hydrogen donor is described. The use of 1,2-bis(dicyclohexylphosphino)ethane (DCyPE), featuring bulky and highly electron-donating properties, led to high catalytic activity. A polystyrene-cross-linking bisphosphine PS-DPPBz produced a reusable heterogeneous catalyst. These homogeneous and heterogeneous protocols achieved chemoselective transfer hydrogenation of alkenes over other potentially reducible functional groups such as carbonyl, nitro, cyano, and imino groups in the same molecule.
- Zhang, Deliang,Iwai, Tomohiro,Sawamura, Masaya
-
supporting information
p. 5867 - 5872
(2019/08/26)
-
- 1,4-Dehydrogenation with a Two-Coordinate Cyclic (Alkyl)(amino)silylene
-
Cyclic (alkyl)(amino)silylene (CAASi) 1 has been found to successfully dehydrogenate 1,4-dihydroaromatic compounds containing various substituents to afford the corresponding aromatic compounds. The observed high substrate generality proves 1 to be a potential 1,4-dehydrogenation reagent for organic compounds. For the reaction with 9,10-dimethyl-9,10-dihydroanthracene, silylene 1 activated not only benzylic C?H bonds but also aromatic C?H bonds to yield a silaacenaphthene derivative, which is an unprecedented reaction of silylenes. The results of the experimental and computational study of the reaction of CAASi 1 with 9,10-dihydroanthracene and 1,4-cyclohexadiene are consistent with the notion that 1,4-dehydrogenation with CAASi 1 proceeds mainly through a stepwise hydrogen-abstraction mechanism.
- Koike, Taichi,Kosai, Tomoyuki,Iwamoto, Takeaki
-
supporting information
p. 9295 - 9302
(2019/07/04)
-
- MICROCAPSULES AND PROCESSES FOR THEIR PREPARATION
-
The present invention provides microcapsules encapsulating hydrophilic or hydrophobic active agents in an inorganic shell, processes for their preparation and compositions comprising them.
- -
-
Page/Page column 43-45
(2019/06/11)
-
- Dehalogenative Deuteration of Unactivated Alkyl Halides Using D2O as the Deuterium Source
-
The general dehalogenation of alkyl halides with zinc using D2O or H2O as a deuterium or hydrogen donor has been developed. The method provides an efficient and economic protocol for deuterium-labeled derivatives with a wide substrate scope under mild reaction conditions. Mechanistic studies indicated that a radical process is involved for the formation of organozinc intermediates. The facile hydrolysis of the organozinc intermediates provides the driving force for this transformation.
- Xia, Aiyou,Xie, Xin,Hu, Xiaoping,Xu, Wei,Liu, Yuanhong
-
p. 13841 - 13857
(2019/10/17)
-
- Design, synthesis, and preliminary biological evaluation of 3′,4′,5′-trimethoxy flavonoid salicylate derivatives as potential anti-tumor agents
-
According to the pharmacophore combination principle, a set of new 3′,4′,5′-trimethoxy flavonoid salicylate derivatives were designed, synthesized, and evaluated for biological activity. The cytotoxicity evaluation revealed that compound 10v exhibited higher potency than 5-Fu against HCT-116 cells. Preliminary biological activity studies showed that compound 10v could inhibit the colony formation and migration of HCT-116 cells. Besides, the Hoechst 33258 staining assay and flow cytometry revealed that treatment with compound 10v induced the apoptosis of HCT-116 cells in a concentration-dependent manner, while it had no effect on their cell cycle. The WB analysis suggested that HIF-1α, tubulin, HK-2, and PFK might be the potential pharmacophore targets of compound 10v. Tubulin was a potential drug target for compound 10v, which was explained by analyzing the crystal structure of compound 10v complexed with tubulin. These results indicated that compound 10v might be a promising anti-tumor agent candidate, deserving further optimization and evaluation.
- Deng, Xiangping,Liu, Renbo,Li, Junjian,Li, Zhongli,Liu, Juan,Xiong, Runde,Lei, Xiaoyong,Zheng, Xing,Xie, Zhizhong,Tang, Guotao
-
p. 1874 - 1884
(2019/01/28)
-
- Sulfonic acid anchored on silica, SiO2@SO3H: A superior solid acid catalyst for quick and solvent-free reductive-deoxygenation of ketones with NaBH3CN
-
NaBH3CN as a modified hydroborate agent and due to a strong withdrawing CN group does not show any reducing ability to reduce functional groups in the absence of acidic media (pH ~ 3–4). In this study, the immobilized sulfonic acid on silica, SiO2@SO3H, was prepared and applied as a new solid acid catalyst for extremely enhancing the reducing ability of NaBH3CN. The influence of SiO2@SO3H was highlighted by performing the quick and green reduction of structurally diverse carbonyl compounds involving aldehydes, ketones, α,β-unsaturated enals and enones, α-diketones, and acyloins to the corresponding alcohols or alkanes with NaBH3CN. By the NaBH3CN/SiO2@SO3H system, aldehydes were reduced to the corresponding alcohols and ketonic compounds to alkanes as reductive-deoxygenation products. All reduction reactions were carried out within 3 min at room temperature and under solvent-free conditions to afford the products in high to excellent yields (90–98%).
- Zeynizadeh, Behzad,Kouhkan, Mehri
-
p. 1521 - 1528
(2018/11/23)
-
- Room Temperature Chemoselective Deoxygenation of Aromatic Ketones and Aldehydes Promoted by a Tandem Pd/TiO2 + FeCl3 Catalyst
-
A rapid and practical protocol for the chemoselective deoxygenation of various aromatic ketones and aldehydes was described, which used a tandem catalyst composed of heterogeneous Pd/TiO2 + homogeneous FeCl3 with the green hydrogen source, polymethylhydrosiloxane (PMHS). The developed catalytic system was robust and scalable, as exemplified by the deoxygenation of acetophenone, which was performed on a gram scale in an atmospheric environment utilizing only 0.4 mol % Pd/TiO2 + 10 mol % FeCl3 catalyst to give the corresponding ethylbenzene in 96% yield within 10 min at room temperature. Furthermore, the Pd/TiO2 catalyst was shown to be recyclable up to three times without an observable decrease in efficiency and it exhibited low metal leaching under the reaction conditions. Insights toward the reaction mechanism of Pd-catalyzed reductive deoxygenation for aromatic ketones and aldehydes were investigated through operando IR, NMR, and GC-MS techniques.
- Dong, Zhenhua,Yuan, Jinwei,Xiao, Yongmei,Mao, Pu,Wang, Wentao
-
p. 11067 - 11073
(2018/09/12)
-
- Transfer Hydrogenation of Alkenes Using Ethanol Catalyzed by a NCP Pincer Iridium Complex: Scope and Mechanism
-
The first general catalytic approach to effecting transfer hydrogenation (TH) of unactivated alkenes using ethanol as the hydrogen source is described. A new NCP-type pincer iridium complex (BQ-NCOP)IrHCl containing a rigid benzoquinoline backbone has been developed for efficient, mild TH of unactivated C-C multiple bonds with ethanol, forming ethyl acetate as the sole byproduct. A wide variety of alkenes, including multisubstituted alkyl alkenes, aryl alkenes, and heteroatom-substituted alkenes, as well as O- or N-containing heteroarenes and internal alkynes, are suitable substrates. Importantly, the (BQ-NCOP)Ir/EtOH system exhibits high chemoselectivity for alkene hydrogenation in the presence of reactive functional groups, such as ketones and carboxylic acids. Furthermore, the reaction with C2D5OD provides a convenient route to deuterium-labeled compounds. Detailed kinetic and mechanistic studies have revealed that monosubstituted alkenes (e.g., 1-octene, styrene) and multisubstituted alkenes (e.g., cyclooctene (COE)) exhibit fundamental mechanistic difference. The OH group of ethanol displays a normal kinetic isotope effect (KIE) in the reaction of styrene, but a substantial inverse KIE in the case of COE. The catalysis of styrene or 1-octene with relatively strong binding affinity to the Ir(I) center has (BQ-NCOP)IrI(alkene) adduct as an off-cycle catalyst resting state, and the rate law shows a positive order in EtOH, inverse first-order in styrene, and first-order in the catalyst. In contrast, the catalysis of COE has an off-cycle catalyst resting state of (BQ-NCOP)IrIII(H)[O(Et)···HO(Et)···HOEt] that features a six-membered iridacycle consisting of two hydrogen-bonds between one EtO ligand and two EtOH molecules, one of which is coordinated to the Ir(III) center. The rate law shows a negative order in EtOH, zeroth-order in COE, and first-order in the catalyst. The observed inverse KIE corresponds to an inverse equilibrium isotope effect for the pre-equilibrium formation of (BQ-NCOP)IrIII(H)(OEt) from the catalyst resting state via ethanol dissociation. Regardless of the substrate, ethanol dehydrogenation is the slow segment of the catalytic cycle, while alkene hydrogenation occurs readily following the rate-determining step, that is, β-hydride elimination of (BQ-NCOP)Ir(H)(OEt) to form (BQ-NCOP)Ir(H)2 and acetaldehyde. The latter is effectively converted to innocent ethyl acetate under the catalytic conditions, thus avoiding the catalyst poisoning via iridium-mediated decarbonylation of acetaldehyde.
- Wang, Yulei,Huang, Zhidao,Leng, Xuebing,Zhu, Huping,Liu, Guixia,Huang, Zheng
-
supporting information
p. 4417 - 4429
(2018/04/05)
-
- Recyclable cobalt(0) nanoparticle catalysts for hydrogenations
-
The search for new hydrogenation catalysts that replace noble metals is largely driven by sustainability concerns and the distinct mechanistic features of 3d transition metals. Several combinations of cobalt precursors and specific ligands in the presence of reductants or under high-thermal conditions were reported to provide active hydrogenation catalysts. This study reports a new method of preparation of small, monodisperse Co(0) nanoparticles (3-4 nm) from the reduction of commercial CoCl2 in the absence of ligands or surfactants. High catalytic activity was observed in hydrogenations of alkenes, alkynes, imines, and heteroarenes (2-20 bar H2). The magnetic properties enabled catalyst separation and multiple recyclings.
- Büschelberger, Philipp,Reyes-Rodriguez, Efrain,Sch?ttle, Christian,Treptow, Jens,Feldmann, Claus,Jacobi Von Wangelin, Axel,Wolf, Robert
-
p. 2648 - 2653
(2018/05/30)
-
- Microwave assisted hydrogenation of olefins by Pd NPs@polystyrene resin using a gas addition kit: A robust and sustainable protocol
-
Polystyrene (PS) resin bead supported palladium nanoparticles (Pd NPs@PS resin) were prepared and their catalytic activity for the hydrogenation of olefins was investigated under microwave heating. The hydrogenation of styrene was effectively carried out in EtOH/H2O, in the presence of 0.00035 mmol of the catalyst to afford the corresponding ethylbenzene in high yield within 20 min under microwave heating. The catalyst efficiency measured in terms of turn over number (TON) and turn over frequency (TOF) was found to be 2829 and 8573 (h-1), respectively. The encapsulated palladium nanoparticles were easily recovered by a simple filtration method and reused several times without significant loss in their catalytic activity. Further, the method showed a wide substrate scope under mild reaction conditions, making it a green versatile and highly sustainable protocol.
- Sharma, Anuj S.,Kaur, Harjinder
-
supporting information
p. 18935 - 18941
(2018/11/27)
-
- Decarboxylation of Lactones over Zn/ZSM-5: Elucidation of the Structure of the Active Site and Molecular Interactions
-
Herein, we report the catalytic decarboxylation of γ-valerolactone (GVL) over Zn/ZSM-5 to butene, followed by aromatization at high yield with co-feeding of water. An evaluation of the catalytic performance after prolonged periods of time showed that a water molecule is essential to maintain the decarboxylation and aromatization activities and avoid rapid catalyst deactivation. Synchrotron X-ray powder diffraction and Rietveld refinement were then used to elucidate the structures of adsorbed GVL and immobilized Zn species in combination with EXAFS and NMR spectroscopy. A new route for the cooperative hydrolysis of GVL by framework Zn?OH and Br?nsted acidic sites to butene and then to aromatic compounds has thus been demonstrated. The structures and fundamental pathways for the nucleophilic attack of terminal Zn?OH sites are comparable to those of Zn-containing enzymes in biological systems.
- Ye, Lin,Song, Qi,Lo, Benedict T. W.,Zheng, Junlin,Kong, Dejing,Murray, Claire A.,Tang, Chiu C.,Tsang, S. C. Edman
-
supporting information
p. 10711 - 10716
(2017/08/30)
-
- Silyloxyarenes as Versatile Coupling Substrates Enabled by Nickel-Catalyzed C-O Bond Cleavage
-
Silyloxyarenes are demonstrated to be a versatile substrate class in a variety of nickel-catalyzed coupling processes. The C(sp2)-O bond of aryl silyl ethers is directly transformed into C-H or C-Si bonds using Ti(O-i-Pr)4 or trialkylsilanes as reagents using nickel catalysts with N-heterocyclic carbene (NHC) ligands. Paired with the useful characteristics of silyl protecting groups, these methods enable protected hydroxyls to directly participate in high-value bond-forming steps rather than requiring deprotection-activation strategies that conventional approaches require. These processes of silyloxyarenes provide reactivity complementary to widely used phenol derivatives such as aryl pivalates, carbamates, and methyl ethers, thus enabling a powerful strategy for sequential chemoselective derivatization of complex substrates without protecting group and activating group manipulations.
- Wiensch, Eric M.,Todd, David P.,Montgomery, John
-
p. 5568 - 5571
(2017/09/15)
-
- A cyclotrimethoxone-substituted salicylate compound and anti-tumor effect thereof
-
The invention relates to the technical field of medicines, and designs and synthesizes a novel A cyclotrimethoxy 4'-hydroxyflavone compound and an A cyclotrimethoxone-substituted salicylate compound. The figure 1 is a general formula of the A cyclotrimethoxone-substituted salicylate compound, wherein in the formula, R1, R2 and R3 are equal to OCH3 or R2, R3 and R4 are equal to OCH3; R5- is equal to OCH3, CH3, F, Cl, Br, I or the like. The novel A cyclotrimethoxy 4'-hydroxyflavone compound and the A cyclotrimethoxone-substituted salicylate compound can have an obvious inhibiting effect on MGC-803 (human gastric carcinoma cells), HepG2 (human hepatoma carcinoma cells), MCF-7 (human breast cancer cells) and hopefully become anti-tumor drugs. The invention discloses a preparation method of the novel A cyclotrimethoxy 4'-hydroxyflavone compound and the A cyclotrimethoxone-substituted salicylate compound.
- -
-
Paragraph 0029-0031
(2017/07/19)
-
- Design, synthesis and biological evaluation of flavonoid salicylate derivatives as potential anti-tumor agents
-
A series of flavonoid salicylate derivatives containing trimethoxybenzene and a series of chrysin salicylate derivatives were synthesized for use as anti-tumor agents, and evaluated for antiproliferative activity using three human tumor cells: MCF-7 (breast carcinoma cells), HepG2 (liver carcinoma cells), MGC-803 (gastric carcinoma cells) and the mice tumor cells MFC (forestomach carcinoma cells). A substituent group of a suitable size and the trimethoxybenzene had a certain influence on the bioactivity of the flavonoid salicylate derivatives. Compound 2 and its salicylate derivatives 7a-7g containing the trimethoxybenzene exhibited more antiproliferative activity. Among them, compound 7g displayed the most potent antiproliferative activity against MGC-803 cells and MFC cells with the concentration causing 50% inhibition of cell growth (IC50) values of 11.05 ± 1.58 μM and 13.73 ± 2.04 μM, respectively. The flow cytometry results showed that compound 7g caused the cell cycle to be arrested in the G0/G1 phase and induced apoptosis of MFC cells in a dose-dependent manner. Furthermore, compound 7g showed good anti-tumor activity in vivo. These results suggested that compound 7g could be a new, potent anti-tumor candidate which should be optimized and evaluated further.
- Deng, Xiangping,Wang, Zhe,Liu, Juan,Xiong, Shujuan,Xiong, Runde,Cao, Xuan,Chen, Yanming,Zheng, Xing,Tang, Guotao
-
p. 38171 - 38178
(2017/08/16)
-
- Hydrogenation of alkenes over nickel nanoparticles under atmospheric pressure of hydrogen
-
Nickel nanoparticles have been shown to be an accessible catalyst which allows hydrogenation of unsaturated compounds to be accomplished under atmospheric pressure of hydrogen at relatively low temperatures. Linear and cyclic alkenes, styrene and norbornene derivatives, as well as pinenes and camphene have been smoothly hydrogenated under these conditions. In some cases, selective hydrogenation of unsaturated carbon–carbon bond is possible with the other functional group remaining intact.
- Mokhov,Popov, Yu. V.,Nebykov
-
p. 319 - 323
(2016/06/06)
-
- Colloidal and nanosized catalysts in organic synthesis: XV. Gas-phase hydrogenation of alkenes catalyzed by supported nickel nanoparticles
-
Gas-phase hydrogenation of alkenes and their derivatives, catalyzed by nickel nanoparticles supported on zeolite or silica gel support occurs at 150–250°С and an atmospheric hydrogen pressure and results in a high conversion. The selectivity of the hydrogenation depends on the amount of hydrogen: at a low diene (triene)–hydrogen ratio, selective hydrogenation of one multiple bond in the substrate is possible.
- Popov, Yu. V.,Mokhov,Nebykov,Latyshova,Panov,Dontsova,Shirkhanyan,Shcherbakova
-
p. 2589 - 2593
(2017/03/22)
-
- Reduced graphene oxide supported nickel-palladium alloy nanoparticles as a superior catalyst for the hydrogenation of alkenes and alkynes under ambient conditions
-
Addressed herein is the superior catalytic performance of reduced graphene oxide supported Ni30Pd70 alloy nanoparticles (rGO-Ni30Pd70) for the direct hydrogenation of alkenes and alkynes to alkanes, which surpasses the commercial Pd/C catalyst both in activity and stability. A variety of cyclic or aromatic alkenes and alkynes (a total of 17 examples) were rapidly reduced to the corresponding alkanes with high yields (>99%) via the presented direct hydrogenation protocol under ambient conditions. Compared to the commercially available Pd/C (10 wt%) catalyst, the rGO-Ni30Pd70 catalyst provided higher yields in shorter reaction times under the optimized conditions. Moreover, the rGO-Ni30Pd70 catalysts were more stable and durable than the commercial Pd/C catalysts by preserving their initial activity after five consecutive runs in the hydrogenation reactions.
- ?etinkaya, Yasin,Metin, ?nder,Balci, Metin
-
p. 28538 - 28542
(2016/04/08)
-
- Alkene hydrogenation over palladium supported on a carbon–silica material
-
Palladium catalysts supported on a carbon–silica material were synthesized. Hydrogenation by molecular hydrogen was studied in the presence of straight-chain and cyclic olefins. As distinct from what is observed for olefins having a phenyl substituent, for aliphatic alkenes the reaction rate decreases with an increasing conversion due to the accumulation of hydrogenation products. The synthesized palladium catalysts show a higher hydrogenation activity than Pd/C.
- Akchurin,Baibulatova,Grabovskii,Talipova,Galkin,Dokichev
-
p. 586 - 591
(2016/10/18)
-
- Method of producing hydrogen of the reaction product and substrate
-
PROBLEM TO BE SOLVED: To provide a new production method requiring no reactor having high stirring power for high-temperature and high-pressure conditions in a gas-liquid catalytic reaction of a liquid phase of a substrate with hydrogen in the presence of a solid catalyst. SOLUTION: Micro or nano bubbles are introduced into a liquid phase consisting of a solvent and a substrate so that a reaction product is produced by gas-liquid contact of the substrate with hydrogen in the presence of the solid catalyst. The substrate is one of organic compounds having an unsaturated carbon bond and secondary and tertiary alcohols. COPYRIGHT: (C)2013,JPOandINPIT
- -
-
Paragraph 0043; 0044
(2017/03/24)
-
- En Route to a Practical Primary Alcohol Deoxygenation
-
A long-standing scientific challenge in the field of alcohol deoxygenation has been direct catalytic sp3 C-O defunctionalization with high selectivity and efficiency, in the presence of other functionalities, such as free hydroxyl groups and amines widely present in biological molecules. Previously, the selectivity issue had been only addressed by classic multistep deoxygenation strategies with stoichiometric reagents. Herein, we propose a catalytic late-transition-metal-catalyzed redox design, on the basis of dehydrogenation/Wolff-Kishner (WK) reduction, to simultaneously tackle the challenges regarding step economy and selectivity. The early development of our hypothesis focuses on an iridium-catalyzed process efficient mainly with activated alcohols, which dictates harsh reaction conditions and thus limits its synthetic utility. Later, a significant advancement has been made on aliphatic primary alcohol deoxygenation by employing a ruthenium complex, with good functional group tolerance and exclusive selectivity under practical reaction conditions. Its synthetic utility is further illustrated by excellent efficiency as well as complete chemo- and regio-selectivity in both simple and complex molecular settings. Mechanistic discussion is also included with experimental supports. Overall, our current method successfully addresses the aforementioned challenges in the pertinent field, providing a practical redox-based approach to the direct sp3 C-O defunctionalization of aliphatic primary alcohols.
- Dai, Xi-Jie,Li, Chao-Jun
-
supporting information
p. 5433 - 5440
(2016/05/19)
-
- Scope and Mechanistic Analysis for Chemoselective Hydrogenolysis of Carbonyl Compounds Catalyzed by a Cationic Ruthenium Hydride Complex with a Tunable Phenol Ligand
-
A cationic ruthenium hydride complex, [(C6H6)(PCy3)(CO)RuH]+BF4- (1), with a phenol ligand was found to exhibit high catalytic activity for the hydrogenolysis of carbonyl compounds to yield the corresponding aliphatic products. The catalytic method showed exceptionally high chemoselectivity toward the carbonyl reduction over alkene hydrogenation. Kinetic and spectroscopic studies revealed a strong electronic influence of the phenol ligand on the catalyst activity. The Hammett plot of the hydrogenolysis of 4-methoxyacetophenone displayed two opposite linear slopes for the catalytic system 1/p-X-C6H4OH (ρ = -3.3 for X = OMe, t-Bu, Et, and Me; ρ = +1.5 for X = F, Cl, and CF3). A normal deuterium isotope effect was observed for the hydrogenolysis reaction catalyzed by 1/p-X-C6H4OH with an electron-releasing group (kH/kD = 1.7-2.5; X = OMe, Et), whereas an inverse isotope effect was measured for 1/p-X-C6H4OH with an electron-withdrawing group (kH/kD = 0.6-0.7; X = Cl, CF3). The empirical rate law was determined from the hydrogenolysis of 4-methoxyacetophenone: rate = kobsd[Ru][ketone][H2]-1 for the reaction catalyzed by 1/p-OMe-C6H4OH, and rate = kobsd[Ru][ketone][H2]0 for the reaction catalyzed by 1/p-CF3-C6H4OH. Catalytically relevant dinuclear ruthenium hydride and hydroxo complexes were synthesized, and their structures were established by X-ray crystallography. Two distinct mechanistic pathways are presented for the hydrogenolysis reaction on the basis of these kinetic and spectroscopic data. (Chemical Equation Presented).
- Kalutharage, Nishantha,Yi, Chae S.
-
supporting information
p. 11105 - 11114
(2015/09/15)
-
- B(C6F5)3-Catalyzed Hydrodesulfurization Using Hydrosilanes - Metal-Free Reduction of Sulfides
-
B(C6F5)3-catalyzed hydrodesulfurization of carbon-sulfur bonds was achieved using triethylsilane as the reducing agent. The corresponding products were obtained in good yields under mild reaction conditions. This protocol could be applied to the reduction of sulfides, including benzyl and alkyl sulfides and dithianes, with high chemoselectivities. (Chemical Equation Presented).
- Saito, Kodai,Kondo, Kazumi,Akiyama, Takahiko
-
p. 3366 - 3369
(2015/07/15)
-
- Palladium nanoparticles supported on fibrous-structured silica nanospheres (KCC-1): An efficient and selective catalyst for the transfer hydrogenation of alkenes
-
An efficient palladium catalyst supported on fibrous silica nanospheres (KCC-1) has been developed for the hydrogenation of alkenes and α,β-unsaturated carbonyl compounds, providing excellent yields of the corresponding products with remarkable chemoselectivity. Comparison (high-resolution TEM, chemisorption) with analogous mesoporous (MCM-41, SBA-15) silica-supported Pd nanocatalysts prepared under identical conditions, demonstrates the advantage of employing the fibrous KCC-1 morphology versus traditional supports because it ensures superior accessibility of the catalytically active cores along with excellent Pd dispersion at high metal loading. This morphology ultimately leads to higher catalytic activity for the KCC-1-supported nanoparticles. The protocol developed for hydrogenation is advantageous and environmentally benign owing to the use of HCOOH as a source of hydrogen, water as a solvent, and because of efficient catalyst recyclability and durability. The recycled catalyst has been analyzed by XPS spectroscopy and TEM showing only minor changes in the oxidation state of Pd and in the morphology after the reaction, thus confirming the robustness of the catalyst.
- Qureshi, Ziyauddin S.,Sarawade, Pradip B.,Albert, Matthias,D'Elia, Valerio,Hedhili, Mohamed N.,K?hler, Klaus,Basset, Jean-Marie
-
p. 635 - 642
(2015/03/05)
-
- PROCESS FOR HYDROGENATION OF OLEFINIC OR ACETYLENIC BONDS
-
The present invention relates to a process for hydrogenation of olefinic or acetylenic bonds. Further, the present invention relates to a process for selective hydrogenation of olefinic or acetylenic bonds and/including triglycerides using modified metal supported on solid acidic metal oxide catalyst and the process for the preparation thereof. The present invention provides a process for hydrogenation of olefinic or acetylenic bonds using metal supported on solid acid metal oxide based catalyst, at moderate conditions. The present invention also relates to the preparation of metal supported on solid acid metal oxide based catalyst for hydrogenation reactions under mild conditions.
- -
-
Paragraph 0071
(2015/09/23)
-
- CATALYST CAPABLE OF FORMING 2,5-DIMETHYLHEXENES
-
A process of making a catalyst and the catalyst composition made by that process comprising a multinuclear metal compound of the formula Ma(PCy3)b(H)c(CO)d(OR)e(H2O)f with molar ratios a:b:c:d:e:f, wherein a is in the range from 2 to 2000, b is in the range from 0 to 4000, c is in the range from 0 to 6000 and d is in the range from 0 to 2000, e is in the range from 1 to 2000, and f is in the range from 0 to 100; wherein PCy3 indicates tricyclohexylphosphine, H indicates hydride, R is an alkyl group determined by the alcohol utilized and H2O is water from the reaction; and a is at least twice w. A method of making one or more 2,5-dimethylhexenes is described. A method of making p-xylene using one or more 2,5-dimethylhexenes is also described.
- -
-
Paragraph 0058
(2015/09/23)
-
- Hydrodecarboxylation of Carboxylic and Malonic Acid Derivatives via Organic Photoredox Catalysis: Substrate Scope and Mechanistic Insight
-
A direct, catalytic hydrodecarboxylation of primary, secondary, and tertiary carboxylic acids is reported. The catalytic system consists of a Fukuzumi acridinium photooxidant with phenyldisulfide acting as a redox-active cocatalyst. Substoichiometric quantities of Hünigs base are used to reveal the carboxylate. Use of trifluoroethanol as a solvent allowed for significant improvements in substrate compatibilities, as the method reported is not limited to carboxylic acids bearing α heteroatoms or phenyl substitution. This method has been applied to the direct double decarboxylation of malonic acid derivatives, which allows for the convenient use of dimethyl malonate as a methylene synthon. Kinetic analysis of the reaction is presented showing a lack of a kinetic isotope effect when generating deuterothiophenol in situ as a hydrogen atom donor. Further kinetic analysis demonstrated first-order kinetics with respect to the carboxylate, while the reaction is zero-order in acridinium catalyst, consistent with another finding suggesting the reaction is light limiting and carboxylate oxidation is likely turnover limiting. Stern-Volmer analysis was carried out in order to determine the efficiency for the carboxylates to quench the acridinium excited state.
- Griffin, Jeremy D.,Zeller, Mary A.,Nicewicz, David A.
-
supporting information
p. 11340 - 11348
(2015/09/21)
-
- Palladium nanoparticles supported on reduced graphene oxide as an efficient catalyst for the reduction of benzyl alcohol compounds
-
Palladium nanoparticles were prepared on reduced graphene oxide (Pd NPs/rGO) by using a sonochemical procedure. Pd NPs with a mean diameter of 37 ± 22 nm were deposited on reduced graphene oxide sheets by the reaction between PdCl42 - and graphene oxide (GO) under sonochemical conditions. The catalyst was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and inductively coupled plasma optical emission spectroscopy (ICP-OES). The Pd NPs/rGO nanocomposite was successfully applied as a reusable catalyst for the reduction of benzyl alcohol derivatives into the corresponding methylene compounds in the presence of triethylsilane. The reductive dehydroxylation of benzyl alcohols takes place under mild conditions affording high yields of the corresponding methylene compounds in short reaction times.
- Mirza-Aghayan, Maryam,Molaee Tavana, Mahdieh,Boukherroub, Rabah
-
-
- Photodriven Transfer Hydrogenation of Olefins
-
An improved practical method for the photodriven diimide reduction of olefins was investigated. This catalyst-free procedure proceeds at ambient temperature, utilizes air as oxidant and a lower hydrazine loading, and produces inert nitrogen gas as the sole byproduct. Several functional groups were tolerated, and in some cases, the reaction was chemoselective. Challenging substrates such as cinnamate ester derivatives and trans-stilbene were reduced in excellent yields. The small amount of UVA rays emitted from a household compact fluorescent light bulb was proposed to enable the cis/trans isomerization of the diimide and to promote the loss of hydrogen from the diimide.
- Leow, Dasheng,Chen, Ying-Ho,Hung, Tzu-Hang,Su, Ying,Lin, Yi-Zhen
-
supporting information
p. 7347 - 7352
(2016/02/18)
-
- Catalyst-free hydrogenation of alkenes and alkynes with hydrazine in the presence of oxygen
-
A series of alkenes and alkynes was subjected to reduction with hydrazine hydrate in ethanol in the presence of oxygen. An efficient method was developed for the reduction of C-C double bonds and C-C triple bonds with diimide, generated in situ from hydrazine hydrate by oxidation with oxygen. The reduction process proceeded for 24-48? hours with high chemoselectivity and excellent yields. This reduction procedure offers synthetic advantages over metal-catalyzed hydrogenation as well as other systems. Georg Thieme Verlag Stuttgart New York.
- Menges, Nurettin,Balci, Metin
-
p. 671 - 676
(2014/04/03)
-
- Immobilization of palladium catalyst on magnetically separable polyurea nanosupport
-
This work describes a method for preparing magnetic polyurea nanoparticles (PU NPs) and their utilization as a catalyst support. The method is based on entrapment of hydrophilic magnetic nanoparticles within the polyurea matrix. The synthetic process of these magnetic polyurea nanoparticles is based on oil-in-oil nanoemulsification of an organic polar phase comprised of N,N-dimethylacetamide (DMAc), 2,6-diaminopyridine and ionic liquid modified magnetite nanoparticles (MNPs-IL), in heptane containing a suitable surfactant. This was followed by interfacial polycondensation reaction between an isocyanate monomer, polymethylenepolyphenyl isocyanate (PAPI 27), and the amine monomer producing magnetically separable polyurea nanoparticles. Subsequently, these particles were employed as a catalyst nanosupport. Two catalytic systems based on the encapsulation of Pd(OAc)2 within magnetic PU NPs or their adsorption on the surface of these particles were produced and subjected to hydrogenation reactions and selective hydrogenations of α,β-unsaturated compounds. Pd(OAc)2 adsorbed on the surface of the magnetic PU NPs demonstrated high catalytic activity and selectivity, which was superior to the conventional catalyst Pd/C or palladium nanoparticles supported directly on the surface of magnetite nanoparticles. The catalyst was easily recovered from the reaction mixture by applying an external magnetic field and recycled over five times without observing any significant loss in its catalytic efficiency. This journal is
- Natour, Suzana,Abu-Reziq, Raed
-
p. 48299 - 48309
(2014/12/10)
-
- Palladium nanoparticles supported on magnesium hydroxide fluorides: A selective catalyst for olefin hydrogenation
-
A one-pot synthesis of palladium nanoparticles supported on magnesium hydroxide fluoride has been performed with the fluorolytic sol-gel method. The prepared catalysts were characterized by using various physicochemical techniques. The sol-gel method led to high surface area (> 135 m2g-1), mesoporous catalysts (pore volume=0.19-0.23 cm3g-1, pore diameter= 3-5 nm) with uniformly dispersed palladium nanoparticles approximately 2 nm in diameter on the surface. The catalysts synthesized by using different concentrations of aqueous hydrofluoric acid exhibited changing surface and acidic properties. Very high dispersion of palladium on magnesium fluoride (47%) was obtained with 1 wt% palladium loading. The catalysts were used for hydrogenation of various olefins in the presence of other organic functionalities at room temperature and atmospheric hydrogen pressure. Various substituted olefins were hydrogenated with almost 100% conversion and selectivity. The catalysts were recycled efficiently over five cycles without appreciable loss in catalytic activity. There was no palladium leaching under the reaction conditions, which was confirmed by inductively coupled plasma atomic emission spectroscopy analysis. Activation of olefin on the catalyst surface could not be observed by in situ FTIR studies, indicating facile activation of hydrogen on the palladium supported on magnesium hydroxide fluoride.
- Acham, Vaibhav R.,Biradar, Ankush V.,Dongare, Mohan K.,Kemnitz, Erhard,Umbarkar, Shubhangi B.
-
p. 3182 - 3191
(2015/02/05)
-
- Microwave flash pyrolysis: C9h8 interconversions and dimerisations
-
The pyrolysis of 2-ethynyltoluene, indene, fluorene, and related compounds has been studied by sealed tube microwave flash pyrolysis (MFP), in concert with modelling of putative mechanistic pathways by density functional theory (DFT) computations. In the MFP technique, samples are admixed with graphite and subjected to intense microwave power (150-300 W) in a quartz reaction tube under a nitrogen atmosphere. The MFP reaction of 2-ethynyltoluene gave mostly indene, the product of a Roger Brown rearrangement (1,2-H shift to a vinylidene) followed by insertion. An additional product was chrysene, the likely result of hydrogen atom loss from indene followed by dimerisation. The intermediacy of dimeric bi-indene structures was supported by pyrolysis of bi-indene and by computational models. Benzo[a]anthracene and benzo[c]phenanthrene are minor products in these reactions. These are shown to arise from pyrolysis of chrysene under the same MFP conditions. MFP reaction of fluorene gave primarily bi-fluorene, bifluorenylidene, and dibenzochrysene, the latter derived from a known Stone-Wales rearrangement.
- Ajaz, Aida,Voukides, Alicia C.,Cahill, Katharine J.,Thamatam, Rajesh,Skraba-Joiner, Sarah L.,Johnson, Richard P.
-
p. 1301 - 1308
(2014/11/07)
-
- Palladium nanoparticles in glycerol: A versatile catalytic system for C-X bond formation and hydrogenation processes
-
Palladium nanoparticles stabilised by tris(3-sulfophenyl)phosphine trisodium salt in neat glycerol have been synthesised and fully characterised, starting from both Pd(II) and Pd(0) species. The versatility of this innovative catalytic colloidal solution has been proved by its efficient application in C-X bond formation processes (X=C, N, P, S) and C-C multiple bond hydrogenation reactions. The catalytic glycerol phase could be recycled more than ten times, preserving its activity and selectivity. The scope of each of these processes has demonstrated the power of the as-prepared catalyst, isolating the corresponding expected products in yields higher than 90%. The dual catalytic behaviour of this glycerol phase, associated to the metallic nanocatalysts used in wet medium (molecular- and surface-like behaviour), has allowed attractive applications in one-pot multi-step transformations catalysed by palladium, such as C-C coupling followed by hydrogenation, without isolation of intermediates using only one catalytic precursor. Copyright
- Chahdoura, Faouzi,Pradel, Christian,Gomez, Montserrat
-
supporting information
p. 3648 - 3660
(2014/01/06)
-
- Micro and nanobubble based strategy for gas-liquid-solid multiphase reactions: Palladium-catalysed hydrogenation of carbon-carbon unsaturated bonds
-
An autoclave-free, gas-liquid-solid multiphase hydrogenation of carbon-carbon unsaturated bonds using hydrogen micro and nanobubbles (MNBs) is developed. The process allows the liquid phase of the reaction mixture to maintain a high concentration of hydrogen gas. Georg Thieme Verlag Stuttgart New York.
- Mase, Nobuyuki,Isomura, Shogo,Toda, Mitsuo,Watanabe, Naoharu
-
supporting information
p. 2225 - 2228
(2013/11/06)
-
- Efficient palladium-catalyzed C-O hydrogenolysis of benzylic alcohols and aromatic ketones with polymethylhydrosiloxane
-
A simple method has been developed for the reductive deoxygenation of aromatic ketones and benzylic alcohols in the presence of polymethylhydrosiloxane (PMHS). The reductive deoxygenation of aromatic ketones and benzylic alcohols, including secondary alcohols, to the corresponding methylene hydrocarbons has been achieved in good to excellent yields using palladium chloride (PdCl2) as catalyst and PMHS as hydride source. Such deoxygenations were successfully with aryl alkyl ketones and diaryl ketones, as exemplified by the reductive deoxygenation of acetophenone and benzopheneone, respectively. The corresponding benzylic alcohols and secondary alcohol analogues could also be converted into their respective methylene hydrocarbons by the PdCl2/PMHS system.
- Wang, Hu,Li, Li,Bai, Xing-Feng,Shang, Jun-Yan,Yang, Ke-Fang,Xu, Li-Wen
-
supporting information
p. 341 - 347
(2013/05/08)
-
