ChemCatChem

Pyrolysis of Cellobiose The cover picture shows a likely intra-molecular hydrogen shift during the gas phase pyrolysis of cellobiose, a subunit of cellulose. In the full paper on p. 200 ff., R. S. Assary and L. A. Curtiss report the application of high-level quantum chemical methods to compute the thermodynamics and reaction barriers for the formation of levoglucosenone from cellobiose, which is helpful in finding new experimental routes to this product. The computational studies predict that the ether bond cleavage in cellobiose occurs through internal hydrogen transfer in gas phase and that the activation energy required is similar to that required to activate cellulose. The initials IACT stand for the Institute for Atom-efficient Chemical Transformations, an Energy Frontier Research Center funded by the U.S. Department of Energy.

Cracking the nut: Two related but distinct organocatalytic ring-opening processes are discussed in this review, as renewed interest from researchers and advances in catalyst design have alerted the community to their potential utility.

Tomorrow always dyes! Organic dyes (e.g., Rose Bengal, Eosin Y) have been recently used as versatile photoredox organocatalysts in place of metal complexes (e.g., Ru²⁺ salts). Accordingly, photoinduced electron transfer reactions induced by excited dyes were exploited in various synthetic processes. The reactions were performed under metal-free conditions and visible light irradiation.

Pushing the dominos after 100 years: Almost a century has elapsed since the pioneer one-pot preparation of a racemic functionalized bicyclo[3.2.1]octane nucleus in 1903, and their first metal-catalyzed direct enantioselective synthesis from achiral precursors in 1999. Both metallic and organic catalytic domino transformations are pivotal developments in the direct construction of functionalized bicyclo[3.2.1]octanes from simple achiral precursors.

Oxygen meets its end, or does it? Straightforward Cu-catalyzed preparation of α-ketoamides has been recently achieved through oxidative coupling of aryl acetaldehydes and arylamines by using O₂ as the terminal oxidant. The work represents a remarkable example of a simple and sustainable transformation to yield elaborate and more complex biologically relevant oxidized products from readily available reagents under mild conditions.

Hyping up the iodines: The discovery and development of oxidative coupling reactions catalyzed by inorganic iodine species (i.e., hypoiodite or iodite), which are generated in situ from an iodide ion and hydrogen peroxide or tert-butyl hydroperoxide as an environmentally benign oxidant is highlighted.

Pick of the bunch: Oxidative CH olefination of aminobenzenes with acrylates was achieved using a palladium/molybdovanadophosphoric acid (HPMoV)/2,4,6-trimethylbenzoic acid (TMBA) system under O₂ (1 atm) in DMF. The highly regio- and stereoselective CH olefination of basic substrates such as aminobenzenes is important in organic synthesis; (E)-para-alkenyl-substituted aminobenzenes were produced in high yields.

Alloy, alloy! A cheap magnetic Fe-Ni alloy is prepared using a simple method and applied to the direct arylation of unactivated arenes with aryl halides. The catalyst exhibits excellent activity and can be reused at least eight times without a significant loss of catalytic activity.

An addiction to rhodium: A nicotinamide-independent regeneration approach for enoate reductases is proposed. The transition metal complex [Cp*Rh(bpy)(H₂O)]²⁺ can replace both the nicotinamide cofactor and a corresponding enzymatic regeneration system, which results in a simplified reaction system. This system is characterized and applied to the chemoenzymatic reduction of various conjugated CC double bonds.

Cellobiose jumps the barrier: High-level quantum mechanical studies show that the ether bond cleavage in cellobiose occurs through internal hydrogen transfer in the gas phase and that the activation energy required is similar to that required for activating cellulose. The reaction barriers are computed for various pathways for the formation of levoglucosenone from levoglucosan, and the most likely pathway requires a relatively low activation barrier compared to that for the activation of cellobiose.

The unnatural selection: The use of aluminum triflate as a promoter for the Pd catalyzed methoxycarbonylation of 1-octene allowed an investigation into the role of the acid and counterion on the activity and selectivity of the catalyst. With this promoter there is no counterion effect at all for AcO⁻, p-TsO⁻, MsO⁻, or TfO⁻ counterions. The results imply that the nature of the acid determines catalyst activity, assuming the presence of a weakly coordinating counterion.

Build a base in your base: The synergistic effect of Sr and Mg species acting as heterogeneous catalysts is observed in biodiesel production as it enhances the activity, which is attributable to new strong basic sites as evidenced by using CO₂-TPD measurements and DFT calculations.

Livin′ on the edge: The microdistributions of the Cr-ion complexes were altered by exploiting the opposite charge of the Cr^III and Cr^VI complexes. The microdistributions of the Cr-ion complexes were altered by exploiting the opposite charge of the Cr^III and Cr^VI complexes.

Rule of the platinum overlayer: Several rutile metal oxide-supported n=(1,2,3) platinum overlayers prove, by means of density functional theory calculations, active catalysts for oxygen reduction reaction, with some candidates even surpassing Pt. Catalyst performance is evaluated against Pt(111) skins on Pt₃X (X=Ni, Co, Fe, Ti, Sc and Y), the best known catalysts for the reaction.

The dynamism of gold: The oxidation state of gold in Au/CeO₂ catalysts is determined in situ in the slurry phase of the hydrogenation of nitrobenzene by means of high-resolution X-ray absorption spectroscopy. No evidence has been found that the detected cationic gold contributes to the catalytic activity.

Stuck in the middle with rhodium: The isomerization of allylic alcohols using a rhodium complex immobilized on mesoporous silica materials was studied. The efficiency of the heterogeneous catalyst was influenced by the nature of the ligands and of the material used. Immobilization of the metal complex on AlSBA-15 resulted in a highly active and selective catalyst that can be recycled several times.

The silver that got left behind: The oxidation of CO on nanoporous Au, in particular the activation of molecular O₂, was investigated by a combination of kinetic and TAP measurements. For the stable catalyst, the amount of adsorbed active oxygen is linearly related to the surface Ag content.

And the best supporting catalyst is… The addition of both PO_x and MoO_x can improve the selectivity at the same conversion rate and maintain the stability of the carbon nanotube catalyst. Catalytic performance for the oxidative dehydrogenation of propane is investigated.

The importance of being SBA-16: Co/SBA-16 catalysts are prepared by means of the incipient wetness impregnation method for Fischer–Tropsch synthesis (FTS). Most of the Co₃O₄ nanoparticles are introduced into the SBA-16 cages. High FTS activity and stability are observed on the SBA-16-supported catalyst. SBA-16 support can efficiently prevent the aggregation and sintering of cobalt nanoparticles.