Abstract:Cu nanoparticles prepared by metal vapor synthesis (MVS) were immobilized on 3-aminopropyl-functionalized silica at room temperature. HRTEM analysis of the catalyst showed that the copper nanoparticles are present with mean diameters limited in the range 1.0-4.5 nm. TPR analysis was performed in order to study the oxidation state of the supported copper nanoparticles. The supported catalyst was used both in batch and in a packed-bed reactor for continuous-flow CuAAC reaction. The activation of the copper catal… Show more
“…For example, agarose was a cheap and degradable polysaccharide for the stabilization of active CuNP (CuNPs@agarose) in the size range of 4-8 nm in water under low catalyst loading and mild reaction conditions [148]. The 3-aminopropylsilica support was able to stabilize smaller CuNPs with the size in the range of 1-4.5 nm, leading to very high catalytic activity (productivity up to 1689 mol/mol) in continuous-flow click reaction between phenyl acetylene and benzyl azide [149]. A more recent case showed fluorescent aggregates of hexarylbenzene derivatives serving both as reactors and stabilizers for the preparation of 9-17 nm-sized CuNPs with efficient catalysis of CuAAC reactions in excellent yield under solvent-free conditions [150].…”
Highlights-The review is focused on the mechanistic aspects and recent trends (since 2012) of the metal-catalyzed azide-alkyne cycloaddition (MAAC) so-called "click" reactions with catalysts based on various metals (Cu, Ru, Ag, Au, Ir, Ni, Zn, Ln), although Cu (I) catalysts are still the most used ones.-These MAAC reactions are by far the most common click reactions relevant to the "green chemistry" concept.-Mechanistic investigations are essential to reaction improvements and subsequent applications, and indeed as shown in this review the proposed mechanisms have been multiple during the last decade based on theoretical computations and experimental search of intermediates.-New trends are also presented here often representing both exciting approaches for various applications and new challenges for further mechanistic investigations.
“…For example, agarose was a cheap and degradable polysaccharide for the stabilization of active CuNP (CuNPs@agarose) in the size range of 4-8 nm in water under low catalyst loading and mild reaction conditions [148]. The 3-aminopropylsilica support was able to stabilize smaller CuNPs with the size in the range of 1-4.5 nm, leading to very high catalytic activity (productivity up to 1689 mol/mol) in continuous-flow click reaction between phenyl acetylene and benzyl azide [149]. A more recent case showed fluorescent aggregates of hexarylbenzene derivatives serving both as reactors and stabilizers for the preparation of 9-17 nm-sized CuNPs with efficient catalysis of CuAAC reactions in excellent yield under solvent-free conditions [150].…”
Highlights-The review is focused on the mechanistic aspects and recent trends (since 2012) of the metal-catalyzed azide-alkyne cycloaddition (MAAC) so-called "click" reactions with catalysts based on various metals (Cu, Ru, Ag, Au, Ir, Ni, Zn, Ln), although Cu (I) catalysts are still the most used ones.-These MAAC reactions are by far the most common click reactions relevant to the "green chemistry" concept.-Mechanistic investigations are essential to reaction improvements and subsequent applications, and indeed as shown in this review the proposed mechanisms have been multiple during the last decade based on theoretical computations and experimental search of intermediates.-New trends are also presented here often representing both exciting approaches for various applications and new challenges for further mechanistic investigations.
“…64 The Cu/C system was originally developed by Lipshutz and co-workers as an inexpensive self-stable catalyst, (Figure 15). 93 The analytical data showed that the MVS allowed the deposition of very small copper particles (<5 nm), which were readily oxidized into Cu(I/II) species after being exposed to air. The primary amine groups on the support served not only as a stabilizer of copper nanoparticles, but also as a heterogeneous base enhancing the reactivity in the CuAAC.…”
Section: Alkyne-azide Cycloadditions With Further Heterogeneous Coppementioning
confidence: 98%
“…(Phenyl hydrazine is added to activate the catalyst bed. )93 A copper-containing layered double hydroxide (LDH) was recently employed as heterogeneous catalyst by the Fülöp-group for the synthesis of triazoles in a highpressure/high-temperature continuous-flow reactor (Figure 16). 94 _ENREF_87 The LDH catalyst was readily obtained by controlled co-precipitiation from Cu(NO 3 ) 2 ·3H 2 O and Fe(NO 3 ) 3 ·9H 2 O at alkaline pH 95.…”
Continuous-flow processing offers unprecedented opportunities to accelerate, integrate, simplify, scale-up and automatize chemical reactions, in combination with an inherently safer and 'greener' nature over traditional batch-based syntheses. Triazoles are amongst the most important and most intensively studied heterocycles, thanks to their diverse biological activities and the incredible number of their applications in the labeling, modification and synthesis of various biomolecules, polymers and supramolecular assemblies. Many research groups have demonstrated that both copper-catalyzed and catalyst-free cycloadditions between azides and various dipolarophiles leading to triazoles or triazole-based structures can be greatly facilitated through the beneficial features of continuous-flow processing. The present review therefore surveys the flow chemistry-based approaches for the synthesis of triazoles, covering the most important catalytic and catalyst-free strategies in continuously operated systems published during the past decade.
“…I envisioned that if highly active heterogeneous catalysts could be immobilized inside a microchannel, as shown in the previous section, the Huisgen cycloaddition should be competed instantaneously. [129][130][131][132][133][134][135][136] Herein, I describe the development of the first polymeric membranous copper catalyst-installed microflow reactor, and its applicability to the Huisgen cycloaddition of alkenes and organic azides. A variety of triazoles were quantitatively produced within a residence time of a few seconds by using the membranous copper catalyst-installed microflow reactor.…”
My mission in catalysis research is to develop highly active and reusable supported catalytic systems in terms of fundamental chemistry and industrial application. For this purpose, I developed three types of highly active and reusable supported catalytic systems. The first type involves polymeric base-supported metal catalysts: Novel polymeric imidazole-Pd and Cu complexes were developed that worked at the mol ppm level for a variety of organic transformations. The second involves catalytic membrane-installed microflow reactors: Membranous polymeric palladium and copper complex/nanoparticle catalysts were installed at the center of a microtube to produce novel catalytic membrane-immobilized flow microreactor devices. These catalytic devices mediated a variety of organic transformations to afford the corresponding products in high yield within 1-38 s. The third is a silicon nanowire array-immobilized palladium nanoparticle catalyst. This device promoted a variety of organic transformations as a heterogeneous catalyst. The Mizoroki-Heck reaction proceeded with 280 mol ppb (0.000028 mol%) of the catalyst, affording the corresponding products in high yield.
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