Search

International audience

Rhodium nanoparticles were assembled on carbon nanotubes, and the resulting nanohybrid was studied in the aerobic oxidation of hydroxylamines to nitrones. Two catalytic systems were developed (i.e., direct or co-catalytic) and both operated to provide high yields of the products, under mild conditions, but with their own specificity as regards the kinetics and regioselectivity of the transformation. In addition, the in situ cycloaddition of the produced nitrones with different alkynes was investigated.

International audience; A gold-based nanostructure has been demonstrated as promising materials for the selective electroreduction of CO2 to CO in aqueous conditions. In this work, we present a carbon nanotube-gold nanohybrid as a selective and efficient electrocatalyst for the reduction of CO2 in 0.5 m NaHCO3 . The hybrid material exhibits remarkable activity with a current density of 10 mA cm-2 at -0.55 V versus standard hydrogen electrode with a stable CO production rate (0.52 μmol s-1 ) after 4 h electrolysis. Monodispersed gold nanoparticles anchored on carbon nanotubes through a layer-by-layer method allows very little Au loading and thus minimization of the cost of electrode fabrication with a mass activity up to 100 A g-1 at -0.55 V versus reversible hydrogen electrode. It is 33 times higher than a previous report for monodisperse Au nanoparticles (3 A g-1 ) while ensuring selectivity (70 % faradaic yield of CO) at comparable reduction potential.

A ruthenium-carbon nanotube nanohybrid was employed as a catalyst in the tandem transformation of nitrochalcones into quinoline N-oxides. Partial reduction of the nitro group to a hydroxylamine, followed by insitu intramolecular condensation to the carbonyl afforded the quinoline-N-oxides in satisfactory to good yields. Reduction of the nitro group was selective and independent of changes in the reaction conditions. Highlights of this method include a very low catalyst loading relative to that required for conventional methods for the synthesis of quinoline N-oxides and mild reaction conditions.

A layer-by-layer approach is used to anchor small gold nanoparticles onto organic nanotubes resulting from the self-assembly and polymerization of diacetylene-containing nitrilotriacetic amphiphiles. The obtained nanotube–gold hybrid is used as a catalyst for the aerobic oxidation of various silanes. With minimal gold loading (0.05 mol%), all substrates are converted into the corresponding silanols with hydrogen gas as the only by-product. The catalyst operates under mild conditions and can be easily recycled, losing neither activity nor selectivity.

Palladium nanoparticles supported on carbon nanotubes were used in the Tsuji-Wacker oxidation. The palladium-based nanohybrid was found to be very active in combination with cuprous chloride for the selective oxidation of terminal olefins into methyl ketones. The co-catalytic system operates under very mild and sustainable conditions (room temperature, atmospheric pressure, low catalyst loading), as opposed to previously reported catalysts, and can be recycled without any loss in activity. Give it a whack: Palladium nanoparticles supported on carbon nanotubes are used in combination with cuprous chloride for the selective Tsuji-Wacker oxidation of terminal olefins into methyl ketones. The co-catalytic system operates under very mild and sustainable conditions and can be recycled without any loss in activity.

Rhodium nanoparticles were anchored on carbon nanotubes and the resulting nanohybrid was studied as co-catalyst, along with tert-butylcatechol, for the dehydrogenation of various N-heterocycles. The co-catalytic system operates in high yields, under the mildest conditions reported so far, and can be applied to a wide variety of secondary amine-containing scaffolds.

A one-pot oxidation–condensation method for the synthesis of quinoxalines from readily available benzoins or benzhydrols and 1,2-phenylenediamines or 2,3-diaminopyridine by use of a gold–carbon nanotube nanohybrid as a heterogeneous catalyst is reported. Quinoxalines are formed under mild conditions in air and in excellent yields. The simple and efficient methodology offers a safe and sustainable alternative to conventional acid and/or base-catalyzed thermal processes.

The development of a photo-responsive micellar system capable of triggering cell death is reported. Precursors of the micelles are synthesized by connecting a lipophilic chain to a hydrophilic polyethylene glycol via a photo-labile nitrobenzyl group. The resulting amphiphilic units are self-assembled in water forming 12 nm micelles that are readily internalized into cells. Upon photo-irradiation, micelles undergo cleavage and yield a cytotoxic nitrosobenzaldehyde derivative, which significantly inhibits the proliferation of MDA-MB-231 cells under standard in vitro conditions.

International audience; Gold nanoparticles supported on carbon nanotubes were investigated as catalysts in the aerobic oxidation of various substrates (phenols, hydroquinones, catechols, aminophenols, and thiols). The nanohybrid system compares favorably with other supported noble metal catalysts in terms of overall efficacy as it operates at room temperature, under air atmosphere (no external oxidant needed), and can readily be recycled.

Tsuji-Wacker oxidation is a palladium catalyzed aerobic oxidation of olefins which serves as a potential strategy for the synthesis of carbonyl compounds. Functionalized terminal olefins are prone to oxidation and provide either methyl ketones or aldehydes in accordance with Markovnikov or anti-Markovnikov rules, respectively. Recent investigations have focused on regioselective synthesis of ketones/aldehydes. This digest aims to give an overview on recent progress in catalyst system modifications to achieve regioselectivity in Tsuji-Wacker oxidation. In addition, the influence of substrates bearing directing group on Tsuji-Wacker oxidation is briefly described.

This account outlines our recent findings on the supramolecular assembly of gold nanoparticles on carbon nanotubes to provide a nanohybrid structure. The resulting gold–carbon nanotube hybrid is evaluated in the catalysis of various organic reactions. 1 Introduction 2 Assembly of the Nanohybrid Catalyst 3 Characterization of the AuCNT Catalyst 4 Use of the AuCNT Catalyst in Selected Organic Transformations 5 Effect of the Size of the Gold Nanoparticles on the Catalytic Activity of the Nanohybrid 6 Perspectives 7 Conclusion

Haplophytine (1) is a heterodimeric alkaloid found in the leaves of the Mexican plant Haplophyton cimicidum. Haplophytine possesses an intriguing complex skeleton which can be subdivided into two domains: a left-hand domain made of a tetracyclic heterocycle, which includes a bridged ketone, and a right-hand indolic domain known as aspidophitine, which incorporates a fused lactone. The two domains are connected at a quaternary carbon center. Upon exposure to HBr, haplophytine undergoes a unique 1,2-rearrangement leading to the imminium compound 2 (Scheme 1). This process is reversible under mildly basic conditions by a

Palladium nanoparticles supported on carbon nanotubes were used in the Tsuji-Wacker oxidation. The palladium-based nanohybrid was found to be very active in combination with cuprous chloride for the selective oxidation of terminal olefins into methyl ketones. The co-catalytic system operates under very mild and sustainable conditions (room temperature, atmospheric pressure, low catalyst loading), as opposed to previously reported catalysts, and can be recycled without any loss in activity. Give it a whack: Palladium nanoparticles supported on carbon nanotubes are used in combination with cuprous chloride for the selective Tsuji-Wacker oxidation of terminal olefins into methyl ketones. The co-catalytic system operates under very mild and sustainable conditions and can be recycled without any loss in activity.

Deoxygenation of a variety of aromatic and aliphatic amine N-oxides has been carried out in excellent yield using dimethylphenylsilane as the reducing agent under the catalytic influence of a carbon nanotube–gold nanohybrid at room temperature. Low catalyst loading, good TON and TOF values, and recyclability of the catalyst are some of the salient features of our methodology.

Starting from diamines, the simple and efficient methodology offers an access to quinoxalines in high yields regardless of whether benzoins or benzhydrols are used as reaction partners, but with the latter requiring longer reaction times.

The N-formylation of primary and secondary amines proceeds in the presence of the recyclable (4 cycles) catalyst with excellent chemoselectivity under mild reaction conditions.

Indo-French Centre for the Promotion of Advanced Research (IFCPAR)/Centre Franco-Indien pour la Promotion de la Recherche Avancee (CEFIPRA) [4705-1]

Yes they can! The groups of Zhu and Ma recently reinvestigated the synthetic route to aspidophilline A. These approaches are discussed in the context of the first total synthesis of the title alkaloid that was reported by Garg and co-workers in 2011.

This paper describes two simple procedures for the one pot synthesis of labelled α-aminophosphates using deuterated acetic acid as labelling source. The reaction of alkyl phosphites with α-iminoacids is studied in some detail. Copyright © 2000 John Wiley & Sons, Ltd.

The reactivity of triazolinedione (TAD) was investigated in the Diels–Alder reaction with carbon nanotubes. However, an unexpected conversion of TAD into its deaza dimer was observed. ESR spectroscopy suggested that the process was initiated by electron transfer from the nanotubes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

A novel procedure for the synthesis of labelled imines and aldazines, using a Bu3P catalyzed decarboxylation, is described. © 1998 John Wiley & Sons, Ltd.

A novel rearrangement of 2-bromo-1-(bromomethyl)ethyl esters into the corresponding 2-oxopropyl derivatives is reported. The mechanism of this transformation was studied by means of 18 O- and 2 H-labeling experiments. The reaction proceeds through a transient dioxolane intermediate that is hydrolyzed to form the corresponding 2-oxopropyl acetate.

The key intermediate (VII) in the synthesis of title compound (VIII) is prepared via iodolactonization and intramolecular cyclopropanation as the key steps.

This concept article summarizes our recent findings regarding photopolymerized micelles obtained from the self-assembly of diacetylene-containing amphiphiles. Their synthesis and characterization are presented as well as some biomedical applications, such as tumor imaging and drug delivery. Finally, ongoing studies and future challenges are briefly discussed.

A one-pot procedure for the transformation of alcohols into nitriles is described and the mechanism of this novel reaction is discussed.

Many (cis)-cyclopropanes bearing 1-electronwithdrawing and 2-hydroxymethylene groups were synthetised and isomerized under midl acidic conditions to afford the corresponding trans isomers. The mechanism is reported.

Stereospecifically alkylated olefins were synthesized in good yields by reaction of various epoxides with organolithium reagents with concommitant introduction of the alkyl group.

Basic intramolecular ring opening reactions of vicinally substituted acceptor-donnor ( trans )-cyclopropanes were studied. An application to the diastereoselective synthesis of (cis)-1-EWG-2-hydroxymethylcyclopropanes is presented.

Allylic alcohols are synthesized by treatment of α-alkyloxy-epoxides with organolithium reagents; The reaction proceeds via a carbenoid pathway.

Copper(II)-mediated alkylation of amines and related compounds (e.g. hydrazines, hydrazones, hydroxylamines) using an alkyl aluminum reagent is described. The reaction proceeds selectively and in good yield, utililizing a metal-metal exchange as the key step.

Intramolecular cyclopropanation reaction of β-γ-unsaturated epoxides yields highly strained tricyclo[4,1,0,0 1,5 ]heptane compounds whose hydrolysis affords α-keto spiro cyclopropanes. Both steps of this one-pot reaction are stereospecific.

A reinvestigation of the copper-mediated phenylation of amines by Biv reagents is reported. The influence of the ligands bound to bismuth and the basicity of the amines have been examined. These results, combined with our previous observations, led to the development of a new system for the quantitative phenylation of selected hindered aliphatic and aromatic amines.