Improving the selectivity
and retaining the efficiency of catalysts
are essential for industrial processes and remain a great challenge.
Herein, we developed a facile route to synthesize Pd nanocubes (NCs)
using Eosin Y as the photosensitizer under visible light. Subsequently,
Pd NCs were uniformly loaded on N-doped carbon nanofibrous microspheres
(NCMs) from carbonated chitin microspheres. This Pd NCs@NCM exhibited
high reactivity and selectivity in alkyne semihydrogenation. For example,
the hydrogenations of phenylacetylene to styrene and of 3-phenyl-2-propyn-1-ol
to (Z)-cinnamyl alcohol were 12.9 and 18.3 times
faster with Pd NCs@NCM than with Lindlar catalyst. According to the
Mott–Schottky effect, loading of Pd NCs on N-doped carbon constructed
a rectifying contact and decreased the electron density of Pd NCs.
Density functional theory (DFT) calculations suggested that the high
concentration of holes doped in Pd NCs weakened the interaction of
alkenes on the Pd (100) facet and prevented further hydrogenation
for a long time; this period of durable time is very helpful in chemical
manufacturing. Thus, Pd NCs@NCM maintained both high reactivity and
selectivity in comparison with surface-modified catalysts. This work
provides an alternative strategy to design Mott–Schottky catalysts
for selective hydrogenation reactions.
Oxidative
carbonylation using carbon monoxide has evolved as an
attractive tool to valuable carbonyl-containing compounds, while mixing
CO with a stoichiometric amount of a chemical oxidant especially oxygen
is hazardous and limits its application in scale-up synthesis. By
employing anodic oxidation, we developed an electrochemical palladium-catalyzed
oxidative carbonylation of arylhydrazines with alkynes, which is regarded
as an alternative supplement of the carbonylative Sonogashira reaction.
Combining an undivided cell with constant current mode, oxygen-free
conditions avoids the explosion hazard of CO. A diversity of ynones
are efficiently obtained using accessible arylhydrazines and alkynes
under copper-free conditions. A possible mechanism of the electrochemical
Pd(0)/Pd(II) cycle is rationalized based upon cyclic voltammetry,
kinetic studies, and intermediates experiments.
Tertiary phosphines (III) find widespread use in many aspects of synthetic organic chemistry. Herein, we developed a facile and novel electrochemical oxidative N-H/P-H cross-coupling method, leading to a series of...
1,4-Dicarbonyl compounds are versatile
scaffolds for the heterocycle
synthesis, including the Paal–Knorr reaction. Herein, a feasible
electrosynthesis method to access 1,4-dicarbonyl compounds has been
developed from simple alkynes and 1,3-dicarbonyl compounds. When the
undivided cell is combined with the constant current mode, aryl alkynes
containing numerous medicinal motifs with 1,3-dicarbonyl esters or
ketones react smoothly. External oxidant and catalyst-free conditions
conform to the requirements of green synthesis.
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