1,721,037 research outputs found
Regio- and enantioselective friedel-crafts reactions of indoles to epoxides catalyzed by graphene oxide: a green approach.
No full text
Graphite functionalization by ball milling with sulfur
No full textThe present study reports on ball-milling of high-surface-area graphite in the presence of sulfur, mainly considering high graphite/sulfur (G/S) weight ratios. Graphitic crystallites after co-milling with sulfur maintain essentially unaltered crystalline order while exhibit heavily functionalized lateral edges, mainly by O=S=O and S=O groups. Solvent extraction procedures and thermogravimetric experiments show that co-milled graphite/sulfur samples contain two different kinds of sulfur: an extractable one being only physically adsorbed on graphite (exhibiting a higher thermal stability) and a non-extractable fraction chemically bonded to defective graphitic sites (exhibiting a lower thermal stability).The amount of sulfur covalently bonded to graphite crystallites increases with the co-milling time up to a limit value, which is in the range 3.0-3.5 wt% and is poorly dependent on the starting G/S ratio
Fe<sub>3</sub>O<sub>4</sub> nanoparticles/ethyl acetoacetate system for the efficient catalytic oxidation of aldehydes to carboxylic acids
No full textA new methodology for the oxidation of aldehydes promoted by commercially available Fe33O4 nanoparticles (Fe3O4 NPs) activated by ethyl acetoacetate was developed. The use of ethyl acetoacetate as additive was crucial to achieve high reactivities. All reactions were realized under solvent free conditions, using air or tBuOOH as oxidants. Finally, the separation and reuse of the magnetically recoverable nanoparticles make this methodology very practical, simple and economical
Oxidized Carbon Black as Catalysts for the Enamine Formation in Solvent-Free Conditions: A Green Strategy to Build the Benzodiazepine Scaffold
No full textOxidized carbon black efficiently catalyzed addition of amines
to 1,3-dicarbonyl compounds under solvent-free conditions at
room temperature. This methodology is eco-friendly and cheap,
with a very easy work up and the possibility to recover and
recycle the catalyst. Finally, the elaborated methodology can be
conveniently exploited for the synthesis of 1,5-benzodiazepine
Vinylogous Aldol Reaction of a Silyloxydiene Promoted by Sulfoxides, as Lewis Bases: 1,4-asymmetric Induction Mediated by a Remote Methylsulfinyl Group
No full textA versatile procedure for the gamma-vinylogous aldol reaction of the dioxinone-derived silyl enolether, via enolate activation with an appropriate neutral Lewis base, was formulated. High levels of diastereo- and enantioselectivity using chiral 2-methylsulfinyl benzaldehyde were obtained, pointing out the dual role of the methylsulfinyl group as incorporated chiral inductor and activator of the silyloxydiene in the stereoselective vinylogous aldol reaction
Thermally stable, solvent resistant and flexible graphene oxide paper
No full textThe ability of graphene oxide (GO) aqueous suspensions to form robust GO paper is largely improved by basification of the suspension before processing. In particular, casting procedures, which are generally unsuitable for production of robust GO paper, become suitable for basified GO (b-GO) suspensions, leading to dense and free-standing papers, which are also highly flexible. Thermal or microwave treatments of paper from b-GO suspensions (b-GO paper) easily produce loss in stacking order of graphene oxide layers, with maintenance of a high degree of parallelism (0.6 < f ≡ orientation function < 0.7) with respect to the paper surface. Differently from usual GO papers, b-GO papers maintain their dimensional integrity when thermally treated or when dispersed in organic solvents or in aqueous solutions. Many relevant b-GO features (improved film ability by casting, maintenance of film integrity and reduced deoxygenation by heating and improved solvent resistance) can be rationalized by formation of covalent bridges between GO layers. Infrared spectra and simple chemical arguments suggest that these covalent bridges between GO layers could be mainly constituted by ether bonds
Graphite oxide as catalyst for diastereoselective Mukaiyama aldol reaction of 2-(trimethylsilyloxy)furan in solvent free conditions
No full textAbstract Graphite oxide efficiently promotes the stereoselective Mukaiyama aldol reaction of 2-(trimethylsilyloxy) furan in solvent free conditions assuring a good level of diastereoselectivity. The catalyst can be easily recovered and reused making the procedure cheap and sustainable. The GO ability to control the stereochemical pathway opens new scenes for the possible application in other synthetic transformations
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