Cyclopropanation of Diazoacetate with Olefins

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Catalytic Hydrogenation of Diacetyl Monoxime to Tetramethylpyrazine with the Soluble Transition Metal Catalysts

Tetramethylpyrazine(TMP)isausefulcompoundinfoodindustry'.InrecentyearsithasbeenfoundasanactiveingredientinChuanxi0ng(ligusticumwallichiifranch),whichisatraditionalChineseherb.NowTMPhasbeenwidelyusedinthetreatmentofpatientswithcerebralischemicdiseasesinChina2.OneoftheimportantmethodsforthepreParationoftetramethylpNazineistheselfcondensati0noftwomoleculesof2-aminobutanoneto2,5-dihydrotetramethlipyrazineandsubsequentoxidati0ntoTMP3.2-Aminobutanoneispreparedusuallyinsituviathereductionofthec…     

Hydrogenation and Skeleton Rearrangements of α-Pinene on Heterogeneous Catalysts

Hydrogenation and isomerization of -pinene on heterogeneous catalysts were studied, and conditions were found for hydrogenation of pinene to cis-pinane on nickel catalysts and for its dehydrogenation to p-cymene on decationized zeolite Y.     

A Preferred Intramolecular ‘Ene’ Reaction Between Ketene and Olefin

Aplysin (1), a marine sesquiterpene was isolated from ‘aplysia kurodai’ and its structure was ellucidated by Hirata-et-al¹. They also reported the synthesis of racemic aplysin². Their synthetic route involved cyclopentanone (2) as a well-characterized intermediate. We visualized the synthesis of cyclobutanone (3) and its subsequent conversion to (2) as an attractive alternative. But during our attempts to synthesize the said cyclobutanone, we have come across a very facile intramolecular ‘ene’ reaction between ketene and olefin. We report our unexpected observations in this communication.     

Activity and Selectivity in CO Hydrogenation with Silica-supported Ru-Co Bimetallic Cluster-derived Catalysts

The catalytic performance of bimetallic Ru-Co catalysts prepared from a series of H3Ru3Co(CO)12. RuCo2(CO)11 and HRuCo3(CO)12 in CO hydrogenation was investigated, and it was found that the Ru-Co bimetallic carbonyl cluster-derived catalysts showed a high activity for products, particularly higher oxygenates, compared with the catalysts prepared from impregnation or co-impregnation of monometallic clusters such as [HRu3(CO)11] and Co4(CO)12. The selectivity for oxygenates in CO hydrogenation highly increased with the molar ratio of Co/Ru in the Ru-Co bimetallic cluster to CO/H2 in feed gas. Raising reaction temperature led to an intensive increase of CO conversion and a considerable decrease of selectivity for oxygenates. In situ FT-IR studies revealed that the band at 1584 cm-1 on Ru-Co bimetallic cluster-derived catalysts at 453 K under syngas (CO/H2 = 0. 5) has a good linear relationship to rates of oxygenate formation, which is likely associated with an intermediate to produce oxygenates in CO hydro     

Preparation and Characterization of Modified-ZrO2 Catalysts for the Reaction of Co Hydrogenation

ZrO2 in different structures and CexZr4-xO8 solid solutions have been prepared by a sol-gel related method with propionic acid as the solvent.The results of their characterization and CO hydrogenation performance eveluation show that ｔ-ZrO2 has better catalytic performance for CO hydrogenation to hydrocarbon than ｍ-ZrO2.Cerium(Ⅲ）acetate and zirconium (Ⅵ）acetylacetonate have been chosen as the most suitable starting materials for CexZr4-xO8 solid solution preparation.Ce-Zr reducibility properties are increased by the incorporation of zirconium oxide in the ceria structure.Ce2Zr2O8 exhibits a higher activity,lower methane selectivity and higher iso-C4 selectivity than tetragonal ZrO2.This implies that the formation mechanism of C4 hydrocarbons,especially that for the iso-C4 fraction is different over Ce2Zr2O8 and t-ZrO2.     

Efficient Cluster-Based Catalysts for Asymmetric Hydrogenation of α-Unsaturated Carboxylic Acids

The new clusters [H(4) Ru(4) (CO)(10) (μ-1,2-P-P)], [H(4) Ru(4) (CO)(10) (1,1-P-P)] and [H(4) Ru(4) (CO)(11) (P-P)] (P-P=chiral diphosphine of the ferrocene-based Josiphos or Walphos ligand families) have been synthesised and characterised. The crystal and molecular structures of eleven clusters reveal that the coordination modes of the diphosphine in the [H(4) Ru(4) (CO)(10) (μ-1,2-P-P)] clusters are different for the Josiphos and the Walphos ligands. The Josiphos ligands bridge a metal-metal bond of the ruthenium tetrahedron in the "conventional" manner, that is, with both phosphine moieties coordinated in equatorial positions relative to a triangular face of the tetrahedron, whereas the phosphine moieties of the Walphos ligands coordinate in one axial and one equatorial position. The differences in the ligand size and the coordination mode between the two types of ligands appear to be reflected in a relative propensity for isomerisation; in solution, the [H(4) Ru(4) (CO)(10) (1,1-Walphos)] clusters isomerise to the corresponding [H(4) Ru(4) (CO)(10) (μ-1,2-Walphos)] clusters, whereas the Josiphos-containing clusters show no tendency to isomerisation in solution. The clusters have been tested as catalysts for asymmetric hydrogenation of four prochiral α-unsaturated carboxylic acids and the prochiral methyl ester (E)-methyl 2-methylbut-2-enoate. High conversion rates (>94?%) and selectivities of product formation were observed for almost all catalysts/catalyst precursors. The observed enantioselectivities were low or nonexistent for the Josiphos-containing clusters and catalyst (cluster) recovery was low, suggesting that cluster fragmentation takes place. On the other hand, excellent conversion rates (99-100?%), product selectivities (99-100?% in most cases) and good enantioselectivities, reaching 90?% enantiomeric excess (ee) in certain cases, were observed for the Walphos-containing clusters, and the clusters could be recovered in good yield after completed catalysis. Results from high-pressure NMR and IR studies, catalyst poisoning tests and comparison of catalytic properties of two [H(4) Ru(4) (CO)(10) (μ-1,2-P-P)] clusters (P-P=Walphos ligands) with the analogous mononuclear catalysts [Ru(P-P)(carboxylato)(2) ] suggest that these clusters may be the active catalytic species, or direct precursors of an active catalytic cluster species.     

Polymerization of Butadiene Using Ziegler-Natta Catalysts—Recent Developments

The products of Ziegler-Natta catalyzed reactions, including high density polyethylene, polypropylene, and other thermoplastics and elastomers, have become familiar to all. While an enormous volume of experimental work was completed during the 1950s and 1960s, it has only been during the 1970s that the multiplicity of mechanistic schemes developed have been subjected to scrutiny. The majority of these have been concerned with polymerization of ethylene and α-olefins and because they have been adequately reviewed recently, are discussed only briefly here. A similarly large volume of empirical experimental work has enabled commercial production of polybutadiene using stereoregular catalysts. However, the mechanisms involved are of recent development, largely due to the additional configurational complexity of products, the multicompound nature of the catalyst complex, and the susceptibility of the system to contamination. Advances which have been made during the last decade are highlighted, with particular emphasis on those modifications to catalyst or to polymer structure which are of practical importance. In Australia, all production of stereoregular (high cis) polybutadiene is achieved using an aluminum alkyl halide-cobalt salt based catalyst. The fundamental technology of this process is discussed with emphasis upon process control. In particular, the control of molecular weight, processing behavior, and reduction in cross-linked material are included in more recent developments. In a broader context, technological changes which have been stimulated by such diverse influences as the increased awareness of industrial hygiene, fluctuations in feedstock availability and cost, and the general acceptance of radial ply tires are discussed. Experimental activities currently in progress in Australia, together with challenges still remaining, are examined.     

Enantioselective Total Synthesis of (−)-Finerenone Using Asymmetric Transfer Hydrogenation

(−)-Finerenone is a nonsteroidal mineralocorticoid receptor antagonist currently in phase III clinical trials for the treatment of chronic kidney disease in type 2 diabetes. It contains an unusual dihydronaphthyridine core. We report a 6-step synthesis of (−)-finerenone, which features an enantioselective partial transfer hydrogenation of a naphthyridine using a chiral phosphoric acid catalyst with a Hantzsch ester. The process is complicated by the fact that the naphthyridine exists as a mixture of two atropisomers that react at different rates and with different selectivities. The intrinsic kinetic resolution was converted into a kinetic dynamic resolution at elevated temperature, which enabled us to obtain (−)-finerenone in both high yield and high enantioselectivity. DFT calculations have revealed the origin of selectivity.     

Differential Selectivity of Palladium–Phosphorus Catalysts in the Competitive Hydrogenation of Isomeric Chloronitrobenzenes

The competitive hydrogenation of сhloronitrobenzene isomers in the presence of different palladium- containing catalysts was studied. The nature of catalytic activity carriers for the Pd–P nanoparticles containing both Pd(0) clusters and palladium phosphides was determined by the method of phase trajectories. It was found that the hydrogenation of сhloronitrobenzene isomers under mild conditions occurred on the clusters of Pd(0), and the dependence of the differential selectivity of Pd–P clusters in the hydrogenation of o- and m-сhloronitrobenzene on the P/Pd ratio was related to the dispersity of the Pd(0) clusters.     

Effect of Transition Metals on Selective Hydrogenation of Cinnamaldehyde over Pt／ZrO2 Catalysts

The effect of transition metals (Cr, Mn, Fe, Co and Ni) on the hydrogenation of cinnamaldehyde over Pt/ZrO2 catalysts was studied in ethanol at 343K under 2.0MPa H2 pressure. PtCo/ZrO2 and PtFe/ZrO2 catalysts exhibit high selectivity and activity of hydrogenation for C=O (93.8% at 87.3% conversion and 83.6% at 88.6% conversion, respectively), and PtNi/ZrO2 exhibits high selectivity of hydrogenation for C=C (64.3% at 70.6% conversion). In the presence of trace H2O and NaOH, over the PtNi/ZrO2 (0.4wt%Ni) catalyst the selectivity to hydrocinnamalde hydereaches 90.6% and the conversion of cinnamaldehyde is 90.5%.     

Simple Reduction of Heteroaromatic Esters to Alcohols Using a Sodium Borohydride–Methanol System

Some heteroaromatic esters were reduced to the corresponding alcohols by using a sodium borohydride–methanol system. The reduction was completed within 0.15–2.0 h in refluxing THF. The alcohol products were isolated after aqueous workup in moderate to excellent yield (48–97%).     

High-Performance Supported Ru Catalysts for the Aqueous-Phase Hydrogenation of Levulinic Acid to γ-Valerolactone

γ-Valerolactone (GVL) can be obtained by efficient hydrogenation of levulinic acid using ruthenium-based catalysts in an aqueous medium. This paper reports an in-depth study on the activity and selectivity of Ru catalysts supported on zirconia-alumina, focusing on the effect of Ru concentration (0.5, 1.5 and 3 wt. % of Ru) and the selection of operational reaction variables. The results showed that the activity strongly depends on the number and oxidation state of the supported ruthenium particles. The most active catalyst, Ru3/ZA, presented the highest number of nanometric particles of zerovalent Ru and the highest number of acid sites. This catalyst gave ca. 100 % selectivity towards GVL, at high conversion of levulinic acid (over 99 %) under the best operating conditions evaluated (120 °C, 3 MPa H₂ pressure, 1 h of reaction, and 0.1 g of catalyst). In addition, this catalyst kept high levels of conversion and selectivity after successive reuse cycles.     

Facile Synthesis of α-Haloketones by Aerobic Oxidation of Olefins Using KX as Nonhazardous Halogen Source

Summary of main observation and conclusion An operationally simple and safe synthesis of a-haloketones using KBr and KCI as nonhazardous halogen sources is reported.It involves an iron-catalysed reaction of alkenes with KBr/KCl using O2 as terminal oxidant under the irradiation of visible-light.This strategy avoids the risks associated with handling halo-contained electrophiles(Cl2,Br2/NCS,NBS).The process is tolerant to several functional groups,and extended to a range of substituted styrenes in up to 89%yield.A radical reaction pathway is proposed based on control experiments and spectroscopy studies.     

Photoredox Catalytic Pentafluorosulfanylative Domino Cyclization of α-Substituted Alkenes to Oxaheterocycles by Using SF6

Virtually inert sulfur hexafluoride becomes a precious pentafluorosulfanylation agent, if properly activated by photoredox catalysis, to access α-fluoro and α-alkoxy SF₅-compounds. This advanced protocol converts SF₆ in the presence of alkynols as bifunctional C−C- and C−O-bond forming reagents directly into pentafluorosulfanylated oxygen-containing heterocycles in a single step from α-substituted alkenes. The proposed mechanism is supported by theoretical calculations and gives insights not only in the pentafluorosulfanylation step but also into formation of the carbon-carbon bond and is in full agreement with Baldwin's cyclization rules. The key step is a radical type 5-, 6- respectively 7-exo-dig-cyclization. The synthesized oxaheterocycles cannot be simply prepared by other synthetic methods, show a high level of structural complexity and significantly expand the scope of pentafluorosulfanylated building blocks valuable for medicinal and material chemistry.     

Structure and Properties of Sol—Gel Derived CuNiMnZrO2 Catalysts for CO Hydrogenation

Two CuNiMnZrO2 catalysts (crystallized or non-crystallized) were prepared by co-hydrolyzing zirconium n-propoxide with Cu(NO3)2, Mn(NO3)2 and Ni(NO3)2 in an ethanol solution in the presence of diglycol. The physical and chemical properties of the catalysts were characterized using BET, XRD,TEM, XPS and CO-DRIFT techniques. It was found that the non-crystallizied CuNiMnZrO2 catalyst demonstrated highly dispersed active phases and high activity for CO adsorption, which resulted in good performance for synthesis of higher alcohols in CO hydrogenation compared to crystallized CuNiMnZrO2.     

Cobalt-catalyzed Photochemical Methoxycarbonylation of Olefins with Carbon Dioxide under Ambient Conditions

The methoxycarbonylations of cyclohexene and 1-decene with CO2 can take place under ambient conditions by catalysis of [Co]([Co]=Co(acac)2, Co(OAc)2, CoCl2 ) in the presence of ultraviolet irradiation.     

Three-component Oxytrifluoromethylation of Alkenes: Highly Efficient and Regioselective Difunctionalization of CC Bonds Mediated by Photoredox Catalysts

Here comes the sun: A facile vicinal difunctionalization of alkenes, oxytrifluoromethylation, was established by visible-light-driven photoredox catalysis. Judicious choice of the CF(3) source is key. Nucleophiles such as water, alcohols, and carboxylic acids can be used in this highly efficient (2-4?h) and regioselective (100?%) transformation using light-emitting diode (LED) lamps and natural sunlight. SET=single-electron transfer.     

Effect of Support on Catalytic Properties of Platinum-Containing Catalysts in Hydrogenation of a Biphenyl–Diphenylmethane Eutectic Mixture

Russian Journal of Applied Chemistry - Pt/Sup catalysts with SiO2, MCM-48, and Al2O3 supports (Sup) were prepared. The catalysts were studied by methods of low-temperature nitrogen adsorption,...     

Gas Phase Polymerisation of Ethylene with Supported Titanium-Nickel Catalysts

Olefins gas phase polymerization uses generally supported titanium catalyst systems inindustrial production. The polymerization of olefins with late transition metal catalysthas recently attracted considerable interestl-2. The new catalyst family shares many ofthe advantages of metallocene catalysts in terms of activity and control of polymerproperties and, in addition, the new catalysts yield homopolymer of ethylene with veryhigh branching degrees and branching degree can be controlled.A new …