Copper‐in‐Charcoal (Cu/C): Heterogeneous, Copper‐Catalyzed Asymmetric Hydrosilylations

Lipshutz, Bruce H.; Frieman, Bryan A.; Tomaso, Anthony E.

doi:10.1002/anie.200503149

Cited by 119 publications

(44 citation statements)

References 45 publications

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“…These may be supplied by a discrete Cu I complex,(Rostovtsev et al, 2002; Tornøe et al, 2002) by metallic copper(Rostovtsev et al, 2002) or copper-impregnated materials(Lipshutz et al, 2006) that expose cuprous ions to the reaction solution, or, most conveniently, by a mixture of a Cu II salt and a reducing agent, sodium ascorbate being by far the most popular. (Rostovtsev et al, 2002) The development of accelerating ligands for the reaction is primarily driven by the need to maintain a sufficient concentration of Cu I in solution, since copper ions can undergo fast and debilitating redox and disproportionation reactions if not properly bound by chelating ligands.…”

Section: Introductionmentioning

confidence: 99%

Copper‐Catalyzed Azide–Alkyne Click Chemistry for Bioconjugation

Presolski

Hong

Finn

2011

CP Chemical Biology

347

293

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The copper‐catalyzed azide‐alkyne cycloaddition reaction is widely used for the connection of molecular entities of all sizes. A protocol is provided here for the process with biomolecules. Ascorbate is used as reducing agent to maintain the required cuprous oxidation state. Since these convenient conditions produce reactive oxygen species, five equivalents of a copper‐binding ligand are used with respect to metal. The ligand both accelerates the reaction and serves as a sacrificial reductant, protecting the biomolecules from oxidation. A procedure is also described for testing the efficiency of the reaction under desired conditions for purposes of optimization, before expensive biological reagents are used. Curr. Protoc. Chem. Biol. 3:153‐162 © 2011 by John Wiley & Sons, Inc.

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Section: Introductionmentioning

confidence: 99%

Copper‐Catalyzed Azide–Alkyne Click Chemistry for Bioconjugation

Presolski

Hong

Finn

2011

CP Chemical Biology

347

293

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“…The experiments reported by Malkov and Ko covsk y [12h] and by Sun [11a,b,e,f ], indicate that the Lewis base-catalyzed imine reduction with trichlorosilane is not affected by isomeric nonhomogeneity of the starting imines. Thus, for example, imines 9h-9j, which exist as 5 : 2 to 5 : 3 (E/Z) mixtures, were reduced to the corresponding amines with 94-97% ee (Table 4.5, entries 8-10).…”

Section: Mechanistic Considerationsmentioning

confidence: 99%

“…Imine a) The reaction was carried out at 0.2 mmol scale (entries 1-12 and 26-34) or 0.4 mmol scale (entries 13-25) with 2.0 equiv of Cl 3 SiH at rt for 16 h unless stated otherwise; see Refs [12c,e,f,i,j]. b) Isolated yield.…”

Section: Entrymentioning

confidence: 99%

Reduction of Imines with Trichlorosilane Catalyzed by Chiral Lewis Bases

Kočcovský

Stončcius

2010

Chiral Amine Synthesis

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j131By contrast, metal-free organocatalysts [6] can be viewed as an attractive alternative to those processes in which the metal is not vital for the key bond-forming event. The advantages are obvious: no metal leaching to the product, reduced toxicity, and lower cost of the catalysts and their regeneration. Therefore, the prime goal here is to develop new, robust processes that could compete with their established, metalcatalyzed counterparts.Silanes are widely recognized as efficient reagents for reduction of carbonyl and heterocarbonyl functionality. In the case of alkyl-and arylsilanes, the reaction requires catalysis by Lewis acids or transition metal complexes [1,3]; however, with more Lewis acidic trichloro-or trialkoxysilanes, an alternative metal-free activation can be accomplished. Thus, it has been demonstrated that extracoordinate silicon hydrides, formed by the coordination of silanes to Lewis bases, such as tertiary amines [7a], DMF [7b] or MeCN, and so on [7], can serve as mild reagents for the reduction of imines to amines [8]. In the case of trichlorosilane, an inexpensive and relatively easy-to-handle reducing reagent, and DMF as a Lewis basic promoter, the intermediacy of hexacoordinate species has been confirmed by 29 Si NMR spectroscopy [7b]. Formamides as Lewis-Basic Organocatalysts in Hydrosilylation of IminesScheme 4.2 Preparation of amines by asymmetric reduction of imines generated from prochiral ketones. For R 1 , R 2 , and R 3 , see Tables 4.

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“…suggested as different types of copper oxides, including Cu 2 O, bound within the charcoal matrix 89,90. _ENREF_82 Optimization of the benzyl azide-phenylacetylene model reaction in acetone as solvent rapidly resulted in quantitative conversion and yield at 170 °C, 20 bar and a flow rate of 1.5 mL min -1 , corresponding to a markedly short residence time of ~12 s. The authors established that the catalysis in the course of the continuous process predominantly operated in the homogeneous phase, due to leaching of the catalytically active copper species from the heterogeneous Cu/C.…”

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confidence: 99%

Flow chemistry as a versatile tool for the synthesis of triazoles

Ötvös

Fülöp

2015

Catal. Sci. Technol.

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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.

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Copper‐in‐Charcoal (Cu/C): Heterogeneous, Copper‐Catalyzed Asymmetric Hydrosilylations

Cited by 119 publications

References 45 publications

Copper‐Catalyzed Azide–Alkyne Click Chemistry for Bioconjugation

Copper‐Catalyzed Azide–Alkyne Click Chemistry for Bioconjugation

Reduction of Imines with Trichlorosilane Catalyzed by Chiral Lewis Bases

Flow chemistry as a versatile tool for the synthesis of triazoles

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