Asymmetric oxidations of organic compounds are limited in their synthetic scope and by practical factors, such as the use of complex catalyst synthesis. A simple and cheap nanostructured catalyst system comprising magnetite nanoparticles stabilized by L-(+)-tartaric acid (Fe3O4/tart-NPs) were successfully synthesized in diethylene glycol. The catalyst was characterized by FT-IR, TGA, ICP-AES, XRPD, SEM and dynamic light scattering (DLS). Catalytic activity of Fe3O4/tart-NPs dispersion in acetonitrile in the presence of isobutyralhyde was studied in selective aerobic oxidation of olefins to form asymmetric epoxide, an important intermediate for the synthesis of biologically active compounds. In addition, the magnetically recoverable nanocatalyst Fe3O4/tart-NPs can be conveniently separated and recovered from the reaction system by applying an external magnetic field and reused for five cycles without the loss of activity after each cycle. These results demonstrate that the heterogeneous nanocatalysts possess potential applications for green and sustainable development. As synthesized nanoparticles of Fe3O4/tart-NPs are a chip and easy to synthesize asymmetric catalyst which were prepared without involvement of difficult and cumbersome procedure for the synthesis of complicated asymmetric ligands. Possible reaction mechanisms were outlined.
The
oxidative cleavage of alkenes to the corresponding aldehydes using
new amphiphilic carbon quantum dots (A-CQDs) as a pseudohomogeneous
carbocatalyst is achieved for the first time through green and sustainable
chemical processes. In this work, we successfully design a recyclable
pseudohomogeneous catalyst based on A-CQDs, which is decorated with
1-aminopropyl-3-methyl-imidazolium chloride and stearic acid. The
functionalization is conducted to introduce a hydrophilic/hydrophobic
functionality on the surface of the catalyst to achieve high catalyst
availability in polar and nonpolar media with the green goal of eliminating
organic (co)solvents and additives. This amphiphilic carbocatalyst
provides high mass transferability to the biphasic system, which is
beneficial to promoting the oxidative cracking of a variety of olefins
into corresponding aldehydes with a substrate/A-CQD ratio of 150.
Around 87% of the substrates are converted to the related aldehydes
using the carbocatalyst in the presence of H2O2, in pure water, without using a phase-transfer catalyst or any additives
and organic solvents, which is comparable with the current metal-based
cleavage systems. Surprisingly, A-CQDs exhibit high catalytic activity
for the scission of electron-deficient CC bond of coumarin
derivatives, accompanied by the cleavage of C–O bonds to produce
the corresponding salicylaldehyde derivatives without overoxidation
to acid. As a brief conclusion, A-CQDs exhibit high conversion efficiency
without significant loss of activity even after six catalytic cycles.
The conversion of alkenes into aldehydes is fast and high-throughput
without overoxidation to acids and is accompanied by excellent solubility
and stability in various solvents. Moreover, the product and the catalyst
are recoverable from the reaction medium by simple extraction. So,
this pseudohomogeneous carbocatalyst promises new horizons in imminent
“catalytic
age”. All in all, this paper provides a significant and novel
advancement in carbocatalyst chemistry.
Herein, we present an interesting role of tungstate-decorated amphiphilic carbon quantum dots (A-CQDs/W) in the selective oxidative cleavage of alkenes to aldehydes. In this work, for the first time, we disclose an unprecedented tungstate-based oxidative system incorporating A-CQDs as a bridge to the homogeneous catalyst for selective and efficient cleavage of a wide substrate scope of alkenes into aldehydes. The A-CQDs/W were synthesized via a one-step hydrothermal synthesis approach using 1-aminopropyl-3-methyl-imidazolium chloride and stearic acid for the surface modification, following by anion-exchange to immobilize WO4–2 to A-CQDs. The A-CQDs/W act as a pseudohomogeneous metallic catalyst (PMC) for selective oxidative scission of alkenes under phase transfer catalysts (PTC) free condition without over oxidation to acids, using water and H2O2 as a green oxidant. Thanks to the sub-nanometric size and novel engineered chemical structure, this PMC and reactants are in the same phase, besides they can be easily isolated from each other by extraction processes. The synthesized PMC exhibited excellent solubility and stability in various solvents. Interestingly, the system’s high conversion efficiency was preserved even after eight catalytic cycles indicating the recyclability of the synthesized PMC. We believe that this study provides a significant and conceptually novel advance in oxidative cleavage chemistry.
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