Title Catalysts Research Articles

Reaction Mechanism and Kinetics for the Selective Hydrogenation of Carbon Dioxide to Formic Acid and Methanol over the [Cu2]0,±1 Dimer.

With the rapid growth of industrialization, deforestation, and burning of fossil fuels, undeniably there has been an incredible escalation of the CO2 concentration in the atmosphere. In order to mitigate the problem, the capture and utilization of CO2 in different value-added chemicals have thus remained topics of concerned research for more than a decade. Accordingly, we have performed molecular -level catalytic hydrogenation of CO2 to formic acid using bare [Cu2]0,±1 dimers as catalysts. The entire investigation has been performed using a density functional theory (DFT) method employing the Perdew-Burke-Ernzerhof (PBE) functional with the def2TZVPP basis set to explore the different possible routes and efficiency of the catalysts. Results reveal the feasibility of H2 dissociation on all three Cu2, Cu2+, and Cu2- dimers. The negatively charged hydride formed during H2 dissociation on Cu2 and Cu2+ dimers facilitates the formation of the HCOO* intermediate over COOH*, thereby providing product selectivity for HCOOH above CO. However, the reaction on the Cu2- dimer forms both HCOO* and COOH* intermediates, but HCOO*, being kinetically more favorable, results in HCOOH production. The free-energy change suggests that the complete reaction on Cu2 and Cu2+ dimers forms a stable product compared to the Cu2- dimer. Furthermore, H3COH production is studied using the title catalysts via the obtained HCOOH* intermediate from the reaction channel. Transition state theory (TST) has been considered to evaluate the rate constants for each step of the reaction. Overall results suggest Cu2 to be better compared to Cu2+ and Cu2- dimers for HCOOH formation and Cu2+ over Cu2 and Cu2- dimers to be more efficient for H3COH formation. This work opens the way for further investigation of the reaction mechanism and development of an efficient catalyst for CO2 hydrogenation.

Hydroformylation of vinyl acetate and cyclohexene over TiO2 nanotube supported Rh and Ru nanoparticle catalysts.

TiO2 nanotube (TNT) supported Rh and Ru nanoparticle catalysts were prepared via impregnation-photoreducing procedure and characterized with various methods. Their catalytic performances in hydroformylation were evaluated by using vinyl acetate and cyclohexene as substrates. The results indicate that the presence of Ru in the catalysts can enhance the catalytic activity of catalysts for the hydroformylation of vinyl acetate, but do not play the same role in the hydroformylation of cyclohexene; the sequence of loading metal has a significant effect on the catalytic performances of the title catalysts. Additionally, it is found that Ru/TNTs shows catalytic activity for the hydroformylation of vinyl acetate though it does not for the hydroformylation of cyclohexene.

ChemInform Abstract: Chiral Pyridinium Phosphoramide as a Dual Broensted Acid Catalyst for Enantioselective Diels—Alder Reaction.

AbstractThe title catalysts are applied in the highly enantioselective Diels—Alder reaction between 1‐amino dienes with maleimides or benzoquinones.

ChemInform Abstract: Design of Highly Stable Iminophosphoranes as Recyclable Organocatalysts: Application to Asymmetric Chlorinations of Oxindoles.

AbstractThe title catalysts are easily available, highly stable, and recyclable.

ChemInform Abstract: Enantioselective Oxidation of Alkenes with Potassium Permanganate Catalyzed by Chiral Dicationic Bisguanidinium.

AbstractThe title catalysts are used for the asymmetric dihydroxylation of α‐aryl acrylates and asymmetric oxohydroxylation of trisubstituted enoates.

ChemInform Abstract: Smaller, Faster, Better: Modular Synthesis of Unsymmetrical Ammonium Salt‐Tagged NHC—Gold(I) Complexes and Their Application as Recyclable Catalysts in Water.

AbstractThe title catalysts are applied in the cyclization reaction of acetylenic carboxylic acids and amides (I), (V) and (III) to lactones (II), (VI), and lactams (IV), respectively.

ChemInform Abstract: Mesoporous CexCo1‐xCr2O4 Spinels: Synthesis, Characterization and Catalytic Application in Simultaneous Removal of Soot Particulate and NO.

AbstractThe title catalysts (x = 0‐0.15) are prepared via combustion of stoichiometric aqueous solutions of the metal nitrates and urea in air and subsequent calcination (600 °C, 4 h).

ChemInform Abstract: tert‐Butyl Ester or Benzylamide of the Dipeptide Pro‐Gly as Organocatalysts for the Asymmetric Aldol Reaction.

AbstractVarious of the title catalysts are synthesized and tested for their catalytic reactivity in the asymmetric aldol reaction.

Cobalt(III) Werner Complexes with 1,2-Diphenylethylenediamine Ligands: Readily Available, Inexpensive, and Modular Chiral Hydrogen Bond Donor Catalysts for Enantioselective Organic Synthesis.

In the quest for new catalysts that can deliver single enantiomer pharmaceuticals and agricultural chemicals, chemists have extensively mined the “chiral pool”, with little in the way of inexpensive, readily available building blocks now remaining. It is found that Werner complexes based upon the D3 symmetric chiral trication [Co(en)3]3+ (en = 1,2-ethylenediamine), which features an earth abundant metal and cheap ligand type, and was among the first inorganic compounds resolved into enantiomers 103 years ago, catalyze a valuable carbon–carbon bond forming reaction, the Michael addition of malonate esters to nitroalkenes, in high enantioselectivities and without requiring inert atmosphere conditions. The title catalysts, [Co((S,S)-dpen)3]3+ ((S,S)-33+) 3X–, employ a commercially available chiral ligand, (S,S)-1,2-diphenylethylenediamine. The rates and ee values are functions of the configuration of the cobalt center (Λ/Δ) and the counteranions, which must be lipophilic to solubilize the trication in nonaqueous media. The highest enantioselectivities are obtained with Λ and 2Cl–BArf–, 2BF4–BArf–, or 3BF4– salts (BArf– = B(3,5-C6H3(CF3)2)4–). The substrates are not activated by metal coordination, but rather by second coordination sphere hydrogen bonding involving the ligating NH2 groups. Crystal structures and NMR data indicate enthalpically stronger interactions with the NH moieties related by the C3 symmetry axis, as opposed to those related by the C2 symmetry axes; rate trends and other observations suggest this to be the catalytically active site. Both Λ- and Δ-(S,S)-33+ 2Cl–BArf– are effective catalysts for additions of β-ketoesters to RO2CN=NCO2R species (99–86% yields, 81–76% ee), which provide carbon–nitrogen bonds and valuable precursors to α-amino acids.

ChemInform Abstract: One‐Step Synthesis of Highly Efficient Nanocatalysts on the Supports with Hierarchical Pores Using Porous Ionic Liquid‐Water Gel.

AbstractThe synthesis of the title catalysts along with their application for the aerobic oxidative esterification of benzyl alcohol and the hydrogenation of benzene to cyclohexane is described.

Catalytic Performance of Silica Supported Cinchona Alkaloids as Heterogeneous Catalysts for Asymmetric Michael Reaction

Silica supported cinchona alkaloids were prepared by thio-ene coupled reaction so as to develop novel highly efficient heterogeneous organocatalysts for asymmetric Michael reaction. As-prepared supported cinchona alkaloids were used as heterogeneous catalysts to catalyze the asymmetric Michael reaction between 1,3-dicarbonyl compounds and N-benzylmaleimide, and their catalytic performance was evaluated. It was found that, when toluene is employed as the solvent, silica supported cinchona alkaloid catalysts can catalyze the aforementioned Michael reaction with medium enantiomeric excess (ee) values (up to 87 %) and significant diastereo ratio (dr) values (up to 96:4). In the meantime, they can be recovered and reused for at least five cycles while their stereo-selectivity remains almost unchanged. This means that the title catalysts could be highly efficient organocatalysts for the investigated Michael reaction.

ChemInform Abstract: Phosphinite‐Iminopyridine Iron Catalysts for Chemoselective Alkene Hydrosilylation.

AbstractThe title catalysts are efficient and selective for the anti‐Markovnikov alkene hydrosilylation of primary, secondary, and tertiary silanes.

ChemInform Abstract: Large yet Flexible N‐Heterocyclic Carbene Ligands for Palladium Catalysis.

AbstractThe title catalysts can be synthesized in eight steps from inexpensive and readily available 2‐nitro‐m‐xylene.

ChemInform Abstract: Crystalline Hybrid Solid Materials of Palladium and Decamethylcucurbit[5]uril as Recoverable Precatalysts for Heck Cross‐Coupling Reactions.

AbstractThe first synthesis of the title catalysts and their application in the Heck cross‐coupling of aryl halides and styrenes is presented.

ChemInform Abstract: Hetero‐Dehydrocoupling of Silanes and Amines by Heavier Alkaline Earth Catalysis.

AbstractThe title catalysts are described as efficient pre‐catalysts for the dehydrogenative coupling of arylsilanes with primary and secondary amines.

ChemInform Abstract: 1,1‐Diamino‐2‐nitroethylenes as Excellent Hydrogen Bond Donor Organocatalysts in the Michael Addition of Carbon‐Based Nucleophiles to β‐Nitrostyrenes.

AbstractThe application of the title catalysts is presented in the Michael—addition of several functionalized nucleophiles to β—nitrostyrenes under mild conditions.

ChemInform Abstract: Multidentate Triphenolsilane‐Based Alkyne Metathesis Catalysts.

AbstractThe title catalysts (I) tolerate many functional groups and have a fast reaction rate and long lifetime, staying active in solution for months.

ChemInform Abstract: Outer Sphere Hydrogenation Catalysis

AbstractReview: 60 refs.

Tungsten‐Based Catalysts for Selective Deoxygenation

On the tip of the tung(sten): The title catalysts selectively perform deoxygenation of vegetable-oil-based feeds by either decarboxylation/decarbonylation or hydrodeoxygenation (HDO) pathways, depending on the dominant tungsten phase (WO3 and W2C). The process upgrades vegetable-oil-based feeds, under a hydrogen atmosphere, to high-value olefinic products, thus providing a significant advantage over other types of deoxygenation catalysts.

Outer sphere hydrogenation catalysis

In the title catalysts, the substrate, typically a ketone, imine or N-heterocycle, remains in the outer sphere (OS). The catalyst transfers hydride and a proton to the unbound substrate either by a concerted or by a stepwise path. These include catalysts not always considered together, such as Bullock's ionic hydrogenation catalysts, bifunctional catalysts in the tradition of Shvo and Noyori and Stephan's frustrated Lewis pair catalysts. By omitting the oxidative addition, insertion and reductive elimination pathways of conventional inner sphere (IS) catalysts, these OS pathways are in principle equally open to inexpensive metals and even nonmetal catalysts. These OS pathways lead to useful selectivity properties, particularly Noyori's asymmetric catalysis, but much more remains to be done in this rapidly developing field.