We report aR h-catalyzedh ydroaminomethylation reaction of terminal alkenes in glycerolt hat proceeds efficiently under mild conditions to produce the corresponding amines in relatively high selectivity towards linear amines, moderate to excellent yields by using al ow catalyst loading (1 mol %[ Rh],2mol %p hosphine) and relative low pressure (H 2 /CO, 1:1, total pressure 10 bar). This work sheds light on the importance of glycerol in enabling enamine reduction via hydrogen transfer.M oreover,e vidence for the crucial role of Rh as chemoselective catalyst in the condensation step has been obtained for the first time in the frame of the hydroaminomethylation reaction by precluding deleterious aldol condensation reactions. The hydroaminomethylation proceeds under am olecular regime;t he outcomeo f catalytically actives peciesi nto metal-based nanoparticles renderst he catalytic system inactive.
Thiolate-capped RhNPs in imidazolium-based ionic liquids were synthesized from [Rh(μ-SR)(COD)]2 dimmers under H2 pressure without external addition of ligand stabilizers, preserving thiolate integrity on the nanoparticle surface. This nanoparticulated systems showed a remarkable selectivity that led to their application in the one pot reductive N-alkylation to produce amines.
In the quest to develop nanometrically defined catalytic systems for applications in the catalytic valorization of agri-food wastes, small Ni-based nanoparticles supported on inorganic solid supports have been prepared by decomposition of organometallic precursors in refluxing ethanol under H2 atmosphere, in the presence of supports exhibiting insulating or semi-conductor properties, such as MgAl2O4 and TiO2, respectively. The efficiency of the as-prepared Ni-based nanocomposites has been evaluated towards the hydrogenation of unsaturated fatty acids under solvent-free conditions, with high selectivity regarding the hydrogenation of C=C bonds. The influence of the support on the catalytic performance of the prepared Ni-based nanocomposites is particularly highlighted.
Rhodium nanoparticles (RhNPs) stabilized with pyridine‐based ligands in the ionic liquid [BMIM][BF4] (RhNPs‐I to III) were synthesized from the organometallic precursor [Rh(µ‐OMe)COD]2 under dihydrogen pressure. The pyridine‐stabilized RhNPs showed smaller size compared to the ligand free RhNPs‐V and presented higher activity and selectivity in the hydrogenation of acetophenone to 1‐phenylethanol. In the case of pyridine‐capped RhNPs‐I, the system was reused for several runs without loss of activity and selectivity. Nitrobenzene was reduced to aniline with dihydrogen in the presence of RhNPs‐I with moderate activity. When the hydrogen source was formic acid‐Et3N azeotrope (transfer hydrogenation) the reaction was completed within minutes with high selectivity. Under transfer hydrogenation conditions, it was possible to apply the catalytic system RhNPs‐I in multistep processes for the generation of substituted arylic amines through the reductive N‐alkylation of nitrobenzene and benzaldehyde; and the synthesis of substituted pyrroles through the nitroarene reduction/Paal‐Knorr condensation.
Environmentally
friendly catalytic composites based on cobalt and
a natural clay as catalytically active phase and support, respectively,
are herein reported for the valorization of fatty acids and esters,
in particular for wastes coming from agri-food industry, by selective
hydrogenation processes. The as-prepared innovative materials are
constituted of zero-valent cobalt nanoparticles immobilized on both
pristine halloysite and an ammonium-functionalized clay, with the
former support exhibiting better particle distribution on the support
as only Co agglomerates could be obtained for ammonium-functionalized
halloysite. Under optimized conditions (5 mol % Co, 120 °C, 40
bar), high conversions and remarkable chemoselectivity were observed,
leading to the exclusive formation of saturated fatty acids or esters,
as well as the formation of tristearin used as a food additive.
Amine and nicotinamide groups grafted on ordered mesoporous silicas (OMS) were investigated as stabilizers for RhNPs used as catalysts in the hydrogenation of several substrates, including carbonyl and aryl groups....
Invited for the cover of this issue is Itzel Guerrero‐Ríos from Universidad Nacional Autónoma de México. The cover image shows a drop of ionic liquid containing pyridine‐stabilized rhodium nanoparticles, whose performance as hydrogenation and transfer hydrogenation catalyst has been investigated.
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