Search

Carbon‐nitrogen bond formation is an important method on both laboratory and industrial scales because it realizes the production of valuable pharmaceuticals, agrochemicals, and fine chemicals. Direct reductive N‐alkylation of amines with carbonyl compounds via intermediary imine compounds, especially under catalytic hydrogenation conditions, is one of the most convenient, economical, and environmentally friendly methods for this process. Here we report a novel palladium species on zirconia having specific activity towards hydrogenation of imines but other carbonyl groups remaining intact. The present catalytic property offers a practical synthetic method of functionalized secondary amines by reductive N‐alkylation under mild conditions with high atom‐efficiency. Mechanistic studies revealed that the catalytically active species is the palladium cluster, which is generated in situ from molecular palladium complexes on the support by exposure to atmospheric hydrogen. These fundamental findings are expected to progress in developing novel cluster catalysts for chemical processes directed towards a sustainable society. [ABSTRACT FROM AUTHOR]

Abstract: Palladium nanoparticles supported on 5 %‐nitrogen‐doped, herringbone‐type carbon nanofibers (Pd/N‐CNF‐H), which are prepared by thermally decomposing [Pd2(dba)3⋅CHCl3] (dba=dibenzylideneacetone) in toluene in the presence of N‐CNF‐H, were found to be an efficient catalyst for the chemoselective hydrogenation of alkenyl and nitro moieties in benzyl‐protected alcohols and carboxylic acid derivatives with high turnover frequencies: the hydrogenation reactions of these functional groups proceeded smoothly even at ambient temperature under atmospheric H2 pressure, and the benzyl protecting groups in the molecules remained intact. Moreover, the recovered Pd/N‐CNF‐H catalyst could be reused without loss of its catalytic activity or chemoselectivity. The Pd/N‐CNF‐H catalyst also acted as an effective hydrogenation catalyst for the reduction of aromatic ketones to the corresponding benzyl alcohol derivatives with good to high product selectivity. [ABSTRACT FROM AUTHOR]

The reaction of three types of carbon nanofibers (CNFs; platelet: CNF-P, tubular: CNF-T, herringbone: CNF-H) with Ir4(CO)12 in mesitylene at 165 °C provided the corresponding CNF-supported iridium nanoparticles, Ir/CNFs (Ir content=2.3-2.6 wt. %). Transmission electron microscopy (TEM) studies of these Ir/CNF samples revealed that size-controlled Ir nanoparticles (average particle size of 1.1-1.5 nm) existed on the CNFs. Among the three Ir/CNF samples, Ir/CNF-T showed an excellent catalytic activity and chemoselectivity towards hydrogenation of functionalized nitroarenes and imines; the corresponding aniline derivatives were obtained with high turnover numbers at ambient temperature under 10 atm of H2, and the catalyst is reusable. Ir/CNF-T was also effective for the reductive N-alkylation of anilines with carbonyl compounds. [ABSTRACT FROM AUTHOR]

The article discusses a study which synthesized palladium nanoparticles supported on nitrogen-doped carbon nanofiber (N-CNF-H) by thermally decomposing Pd2(dba)3CHCl3 in the presence of N-CNF-H. The study found that the Pd/N-CNF-H compounds act as efficient catalysts in the partial hydrogenation of internal alkynes to the corresponding (Z)-alkenes. It also suggested the significance of N-CNF-H in the preparation of heterogenous poisoning catalysts.