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.
In this study, ruthenium-on-carbon-catalyzed hydrogenation of CBDK was developed for the production of cis-CBDO under solvent-free conditions. Isomerization using a ruthenium catalyst and hydrogen gas may improve the selective formation of cis-CBDO. Moreover, the reaction mechanisms for cis-selectivity was proposed based on density functional theory (DFT) calculations.
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.
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