ChemCatChem

Selective Oxidation In their contribution on page 118 ff., Gómez, Serp, and co-workers describe efficient catalysts for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol, the chemical responsible for the hyacinth's scent. Bimetallic platinum/ruthenium nanoparticles stabilized by simple ligands were prepared in both THF and supercritical carbon dioxide, giving more dispersed particles than those prepared in the organic solvent. Their confinement in multi-walled carbon nanotubes could be achieved thanks to the appropriate functionalization of the support by amide groups containing a long alkyl chain. The higher selectivity observed for the confined catalysts in relation to the non-confined ones, can be attributed to the higher concentration of reactants inside the multi-walled carbon nanotubes.

Editorial 2012: A quick rundown of last year and an introduction to the next. Expect more great catalysis, more breakthroughs, and more quality.

The best of two worlds! Both heterogeneous and homogeneous catalyses by gold have well-known advantages. The heterogenization of gold complexes through anchoring on porous solid materials is a way to have “the best of two worlds.” This work reviews the attempts made so far on this important topic. The results obtained show that these hybrid materials can have improved activity and selectivity and are potential choice candidates for several catalytic processes.

Affixation with the monolith: This review elucidates advances in supported catalysis for metathesis, Heck, Suzuki, Sonogashira–Hagihara, and biocatalytic reactions. Syntheses and post-functionalizations of organic polymeric monoliths to affix functional catalysts are described. The function of these porous structures in both heterogeneous catalysis and biocatalysis under continuous flow conditions is illustrated.

And the catalyst goes wild! The results of great interest in the field of hydrogen production catalyzed by using a synthetic nickel electrocatalyst with a fantastic turnover frequency (above 100 000 s⁻¹) have been discussed.

Borylation support group: Sterically demanding aryl chlorides can now be used effectively in the palladium-catalyzed borylation reaction. Phosphanes tethered to a silica support are used in the catalyst system to give aryl boronate esters in high yields.

In the THIQ of it:N-Alkyl tetrahydroisoquinolines are oxidatively coupled with a variety of nucleophiles in the presence of m-CPBA and [VO(acac)₂]. This method has been applied to the synthesis of the opioid methopholine.

Nitrites dominate! Nitrites and nitrates are formed on the catalyst surface upon storage of NO_x over a model Pt–Ba/Al₂O₃ NO_x storage–reduction catalyst. Nitrites are formed through the oxidation of NO at the Pt–Ba interface (nitrite route), while nitrates are formed upon nitrite oxidation and/or NO₂ adsorption following NO oxidation at Pt sites. The nitrite route is the unique pathway responsible for the storage of NO_x at low temperatures, but it also dominates at high temperatures.

Cheers for the support: By varying the support, the hydrogenation of nitrobenzene occurs either through a direct route in the case of Au/TiO₂ catalysts and through a condensation route over Au/CeO₂ catalysts. Adsorption on the surface of the catalysts is discussed as a possible key factor in determining the route.

Suffocating phenols: A catalyst system consisting of Pd/C and HZSM-5 shows an extremely high selectivity in removing oxygen-containing groups (hydroxyl, methoxy, ketone, alkylOaryl, and arylOaryl) in lignin-derived substituted phenolic monomers and dimers through a metal-acid catalyzed cascade cleavage of CO bonds in phenolic dimers and the integrated hydrogenation and dehydration reactions in water at 473 K.

Don't moan, use Ammonia! A general palladium-catalyzed aminocarbonylation of benzyl chlorides using ammonia has been developed. Various primary 2-arylacetamides are synthesized in good to excellent yields and selectivities by using an inexpensive palladium catalyst system for this atom-efficient methodology.

Getting friendly with methanol: The most important challenge in gas phase heterogeneous catalysis is to reach high selectivity in a desired process. Probably the only way to get high selectivity in gas phase heterogeneous catalysis is to work under “friendly temperature conditions”. Methyl formate could be produced directly from methanol with a very high selectivity, over supported palladium nanoparticles at low temperature and under atmospheric pressure.

A race of dwarfs: We have successfully a transition-metal-free catalysis relay method for efficient aerobic oxidation at ambient conditions. The catalysis relay system is a combination of four dependent small molecules that enable the transfer of the oxidative ability of molecular oxygen to the aerobic oxidation of alcohols to their corresponding carbonyl compounds under mild conditions.

Buti in the eye of the beholder: The influence of substituents in ButiPhane ligands on the hydrogenation activity and selectivity of the corresponding rhodium complexes has been quantitatively assessed. In the hydrogenation of a series of prochiral olefins, improved selectivities were obtained by increasing the steric bulk of the substituents on the phospholane ring of the chiral ligand.

Tyrosinase layers it down: Catechols are biologically active, synthetically challenging derivatives. Heterogeneous tyrosinase catalysts obtained through the layer-by-layer technique were applied to the conversion of phenols into the corresponding catechols. The reactions proceeded in high yield and selectivity, avoiding the formation of quinones by the use of mixed solvents. The biocatalysts retained activity over several runs.

The CO terminator: Density functional theory results show that both gas phase CO and adsorbed CO molecules can react with lattice oxygen on oxygen-terminated metal oxides. The catalytic activity of CO oxidation on oxygen-terminated metal oxides is higher than that on metal-terminated metal oxides.

Dressed up for the photoshoot: A stable and efficient homogeneous catalytic system involving 1,3,6,8-pyrenetetrasulfonic acid (PTSA) functionalized Pt nanocomposites as photocatalysts and ethylenediaminetetraacetic acid (EDTA) as a sacrificial reductant in the absence of an electron mediator was prepared.

Into the nanotube: Platinum–ruthenium nanoparticles confined into functionalized multiwalled carbon nanotubes were found to be efficient catalysts for the hydrogenation of cinnamaldehyde in contrast to the unsupported catalytic systems. Although bimetallic nanoparticles synthesized in supercritical CO₂ led to more agglomerated materials than those in THF, no important differences were observed in catalysis.

Stepping onto forgotten paths: A new protocol for the selective Meyer–Schuster rearrangement of propargylic alcohols has been developed by using catalytic amounts of the readily accessible oxovanadate(V) complex [V(O)Cl(OEt)₂].

Foamtastic: A novel method for the preparation of a solid acid foam has been developed. It is based on electrophoretic deposition of zirconium phosphate on metallic foam. Advantages of the coating by electric field led to an area-related catalytic activity about two times higher than that of a bulk catalyst in the fructose dehydration reaction.