Two different types of palladium catalysts supported on dual-pore monolithic silica beads [5% Pd/SM and 0.25% Pd/SM(sc)] for chemoselective hydrogenation were developed. Alkyne, alkene, azide, and nitro functionalities and the...

Palladium catalysts immobilized on cellulose particles (Pd/CLP) and on a cellulose‐monolith (Pd/CLM) were developed. These composites were applied as hydrogenation catalysts and their catalyst activities were evaluated. Although both catalysts catalyzed the deprotection of benzyloxycarbonyl‐protected aromatic amines (Ar‐N‐Cbz) and aromatic benzyl esters (Ar‐CO2Bn), only Pd/CLM could accomplish the hydrogenolysis of aliphatic‐N‐Cbz and aliphatic‐CO2Bn protective groups. The difference in the physical structure of the cellulose supports induced unique chemoselectivity. Aliphatic‐N‐Cbz and aliphatic‐CO2Bn groups were tolerated under the Pd/CLP‐catalyzed hydrogenation conditions, while Ar‐N‐Cbz, Ar‐CO2Bn, alkene, alkyne, azido and nitro groups could be smoothly reduced.

We developed a microwave-mediated continuous hydrogen production method from 2-PrOH using platinum on a spherical carbon-bead catalyst. The catalyst cartridge consisted of helical glass part, and straight glass part (helix−straight cartridge) was newly developed for the effective microwave heating of 2-PrOH in the presence of 5% Pt/CB. The microwave resonance was properly adjusted within 2.4−2.5 GHz using the helix−straight cartridge with the glass resonance-adjuster tube. The reaction was conducted by the irradiation of only 10 W of single-frequency microwaves and the catalyst was used continuously for at least 13 h without any loss of catalyst activity.

A practical and efficient continuous-flow system was developed for the synthesis of site-selectively deuterium-labeled β-nitroalcohols by using the tertiary amine-functionalized basic anion exchange resin, WA30, as a heterogeneous organocatalyst. For this system, WA30 was prepacked in a cartridge under metal-free conditions. The system was operated by pumping a solution of aldehydes or ketones, as electrophiles, and nitroalkanes in a solvent system of deuterium oxide and THF in the catalyst cartridge. Various deuterated β-nitroalcohols were obtained in moderate to excellent yields with high deuteration efficiencies. The continuous-flow system was applied in continuous synthesis for at least 72 h without degradation of the heterogeneous organocatalyst activity.

The synthesis of polycyclic aromatic compounds generally requires stoichiometric oxidants or homogeneous metal catalysts, however, the risk of contamination of inorganic residues can affect their properties. Here we present a microwave (MW)-assisted platinum on beaded activated carbon (Pt/CB)-catalyzed C–C bond formation of diarylacetylenes and aromatic hydrocarbons under continuous-flow conditions. Various fused aromatic compounds were continuously synthesized via dehydrogenative C(sp2)–C(sp2) and C(sp2)–C(sp3) bond formation with yields of up to 87% without the use of oxidants and bases. An activated, local reaction site on Pt/CB in the flow reaction channel reaching temperatures of more than three hundred degrees Celsius was generated in the catalyst cartridge by selective microwave absorption in CB with an absorption efficiency of > 90%. Mechanistic experiments of the transformation reaction indicated that a constant hydrogen gas supply was essential for activating Pt. This is an ideal reaction with minimal input energy and no waste production.

The Cover Feature shows a typical chemoselective hydrogenation scheme catalyzed by cellulose‐supported (represented as a traditional Japanese paper crane) Pd nanoparticles. In their Full Paper, T. Yamada et al. developed two types of chemoselective heterogeneous palladium catalysts, using cellulose particles and monolithic cellulose as supports. The Pd nanoparticles were strongly immobilized on cellulose particles and monolithic cellulose with negligible leaching during hydrogenation reaction. Both catalysts could be reused by simple filtration without degradation of the catalyst activity. Since the use of cellulose results in carbon neutrality and circulates carbon dioxide, it has attracted attention as an alternative to industrially synthesized polymers derived from fossil fuels. More information can be found in the Full Paper by T. Yamada et al.