TEMPO-Functionalized Aromatic Polymer as a Highly Active, pH-Responsive Polymeric Interfacial Catalyst for Alcohol Oxidation

Hu, Kecheng; Tang, Jun; Cao, Shixiong; Zhang, Qi; Wang, JianLi; Ye, Zhibin

doi:10.1021/acs.jpcc.9b00467

Cited by 23 publications

(18 citation statements)

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“…Organocatalysts have been widely used as catalysts for a variety of organic transformations. , Recently, immobilization of organic bases onto polymers for heterogeneous catalysis has attracted great attention because of the convenience of catalyst recycling and high efficiency in catalytic applications . Herein, two important organic base catalysts triethylenediamine (DABCO) and 4-(dimethylamino)pyridine (DMAP) analogues were introduced into the MBs by simple nucleophilic substitution reactions of alkyl halide with amino group from DABCO or hydroxyl group from an DMAP analogue.…”

Section: Results and Discussionmentioning

confidence: 99%

“…9,41 Recently, immobilization of organic bases onto polymers for heterogeneous catalysis has attracted great attention because of the convenience of catalyst recycling and high efficiency in catalytic applications. 42 Herein, two important organic base catalysts triethylenediamine (DABCO) and 4-(dimethylamino)pyridine (DMAP) analogues were introduced into the MBs by simple nucleophilic substitution reactions of alkyl halide with amino group from DABCO or hydroxyl group from an DMAP analogue. The successfully introduction of DABCO can be judged by the shift of the proton signal on the meta methylene group of bromine in CDCl 3 from 4.27 ppm (Figure 2a) to 4.67 ppm (Figure 2b), which was the result of the electronegativity of the nitrogen atom of quaternary ammonium in DABCO being stronger than that of the bromine atom after the nucleophilic substitution reaction, causing the resonance absorption to shift to the lower field and the higher chemical shift.…”

Section: Resultsmentioning

confidence: 99%

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Self-Assembled Catalytic Nanoreactors from Molecular Brushes by Utilizing Postpolymerization Modification for Catalyst Attachment

Wang

Min

Huang

et al. 2022

ACS Appl. Polym. Mater.

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Polymer-based catalytic nanoreactors, with the characteristics of easy preparation, good dispersion, and facile modulation of molecular structures, have been widely applied for various organic transformations. Usually, polymeric nanoreactors are fabricated via the self-assembly of amphiphilic copolymers in water, while the disassembly and instability of the relevant nanoreactors often compromise their potential applicability. Molecular brushes (MBs), as a kind of polymer with high-density grafted side chains on the linear polymer main chain, can be rapidly self-assembled into highly ordered nanostructures even at low concentrations. This study reports the fabrication of catalytic nanoreactors from molecular brushes of poly[norbornene–poly(bromoethyl methacrylate-co-methyl methacrylate)]-co-poly[norbornene polyethylene glycol monomethyl ether] (P[NB-(BEMA-co-MMA)]-co-P[NB-PEG]). The amphiphilic molecular brush was synthesized by combining reversible addition–fragmentation chain transfer (RAFT) polymerization and ring-opening metathesis polymerization (ROMP) techniques. Homogeneous catalysts, such as triethylenediamine and 4-(dimethylamino)pyridine analogues, were introduced by nucleophilic substitution with alkyl bromide on the side chain of molecular brushes. Furthermore, micellar catalytic nanoreactors were fabricated via self-assembly in deionized water. The resulted nanoreactors display high catalytic activities toward the Knoevenagel condensation reaction and acylation reaction of alcohol in water, respectively. This contribution describes a general method for constructing highly efficient molecular brush-based catalytic nanoreactors utilizing postpolymerization modification (PPM) for aqueous catalysis.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Self-Assembled Catalytic Nanoreactors from Molecular Brushes by Utilizing Postpolymerization Modification for Catalyst Attachment

Wang

Min

Huang

et al. 2022

ACS Appl. Polym. Mater.

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“…To this end, various immobilization strategies have been developed. Thus, TEMPO derivatives were immobilized in nanoparticles, nanoparticles/polymers, , fullerene, saponites, gels, − polymers − such as polystyrene, , polystyrene microcapsules, polyurethane, polyethylene glycol, − poly(vinyl alcohol)- graft -poly(ethylene glycol), mesoporous silica (SBA-15 or MCM-41), or silica. − Further, oxidation reactions have been conducted with recyclable TEMPO derivatives entrapped in micellar systems, − nanoreactors, or nanofibers. − …”

Section: Oxidation Reactionsmentioning

confidence: 99%

Organic Synthesis Using Nitroxides

Leifert

Studer

2023

Chem. Rev.

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Nitroxides, also known as nitroxyl radicals, are long-lived or stable radicals with the general structure R 1 R 2 N−O • . The spin distribution over the nitroxide N and O atoms contributes to the thermodynamic stability of these radicals. The presence of bulky N-substituents R 1 and R 2 prevents nitroxide radical dimerization, ensuring their kinetic stability. Despite their reactivity toward various transient C radicals, some nitroxides can be easily stored under air at room temperature. Furthermore, nitroxides can be oxidized to oxoammonium salts (R 1 R 2 N�O + ) or reduced to anions (R 1 R 2 N−O − ), enabling them to act as valuable oxidants or reductants depending on their oxidation state. Therefore, they exhibit interesting reactivity across all three oxidation states. Due to these fascinating properties, nitroxides find extensive applications in diverse fields such as biochemistry, medicinal chemistry, materials science, and organic synthesis. This review focuses on the versatile applications of nitroxides in organic synthesis. For their use in other important fields, we will refer to several review articles. The introductory part provides a brief overview of the history of nitroxide chemistry. Subsequently, the key methods for preparing nitroxides are discussed, followed by an examination of their structural diversity and physical properties. The main portion of this review is dedicated to oxidation reactions, wherein parent nitroxides or their corresponding oxoammonium salts serve as active species. It will be demonstrated that various functional groups (such as alcohols, amines, enolates, and alkanes among others) can be efficiently oxidized. These oxidations can be carried out using nitroxides as catalysts in combination with various stoichiometric terminal oxidants. By reducing nitroxides to their corresponding anions, they become effective reducing reagents with intriguing applications in organic synthesis. Nitroxides possess the ability to selectively react with transient radicals, making them useful for terminating radical cascade reactions by forming alkoxyamines. Depending on their structure, alkoxyamines exhibit weak C−O bonds, allowing for the thermal generation of C radicals through reversible C−O bond cleavage. Such thermally generated C radicals can participate in various radical transformations, as discussed toward the end of this review. Furthermore, the application of this strategy in natural product synthesis will be presented.

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“…From fundamental research to industrial applications, nanomaterials play an important role in multitudinous fields, such as catalysis, − energy storage and conversion, medicine, and environmental protection . As a sustainable alternative for conventional materials, nanocatalysts provide an effective strategy for bridging the gap between homogeneous and heterogeneous catalysis .…”

Section: Introductionmentioning

confidence: 99%

Magnetic Nanoparticles with In Situ Surface Growing Polymeric Brushes as Reactive Pickering Interfacial Catalysts for Biphasic Reactions

et al. 2021

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The intensification of catalytic reaction and droplet manipulation in a liquid–liquid (L–L) biphasic system has been widely focused in this research. The surface engineering of magnetic materials offers a reasonable tactic for the design of magnetic Pickering interfacial catalysts (MPICs), which substantially bridges the gap of homogeneous and heterogeneous catalysis for promoting efficient and selective transformation of resources. In this study, we control the growth of organic base monomer brushes by surface-initiated reversible addition–fragmentation chain transfer (SIRAFT) polymerization to afford a magnetopolymeric nanocatalysts Fe3O4@PS-PM. The surface engineering strategy enables us to simply tune the surface wettability and active site content for the manipulation of emulsion catalysis. In a biphasic reaction system (i.e., transesterification and epoxidation), the catalytic performance of an emulsion system is more than twice that of an unemulsified system, which is attributed to the enhancement effect of the Pickering emulsion microenvironment. In addition, the inherent paramagnetism demonstrates that MPICs can be swiftly desorbed and recovered from the oil–water interface and showed attractive catalytic activity and stability over five runs. The practical surface engineering has promising prospects for construction and adjustment of magnetically separable PICs and enables accessible manipulation of green chemical transformation based on a versatile Pickering emulsion platform.

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TEMPO-Functionalized Aromatic Polymer as a Highly Active, pH-Responsive Polymeric Interfacial Catalyst for Alcohol Oxidation

Cited by 23 publications

References 50 publications

Self-Assembled Catalytic Nanoreactors from Molecular Brushes by Utilizing Postpolymerization Modification for Catalyst Attachment

Self-Assembled Catalytic Nanoreactors from Molecular Brushes by Utilizing Postpolymerization Modification for Catalyst Attachment

Organic Synthesis Using Nitroxides

Magnetic Nanoparticles with In Situ Surface Growing Polymeric Brushes as Reactive Pickering Interfacial Catalysts for Biphasic Reactions

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