Cobalt-Impregnated Magnetite as General Heterogeneous Catalyst for the Hydroacylation Reaction of Azodicarboxylates

Catalysts consisting of cobalt and nickel impregnated on magnetite have been prepared, characterized and used for the hydroacylation reaction of different azodicarboxylate compounds with aldehydes, using nearly stoichiometric amounts of both reagents in only 3 h. Furthermore, this reaction has been conducted with the smallest amount of catalyst. The cobalt catalyst is stable enough to be removed by magnetic decantation and recycled ten-fold without any detrimental effect on the results.This work was supported by the Spanish Ministerio de Economía y Competitividad (MICINN; CTQ2011-24151) and University of Alicante. J. M.P. thanks the MICINN (FPI program) for her fellowship

Iron Oxide Nanoparticles Modified with Carbon Quantum Nanodots for the Stabilization of Palladium Nanoparticles: An Efficient Catalyst for the Suzuki Reaction in Aqueous Media under Mild Conditions

Magnetic Fe3O4 nanoparticles (NPs) functionalized with carbon dots (C-dots) that contain carboxylic acid and hydroxyl groups were synthesized successfully and used for the reduction of PdII and the formation of Pd NPs. The new material was characterized by SEM, TEM, energy-dispersive spectroscopy, solid UV spectroscopy, vibrating sample magnetometry, XRD, and X-ray photoelectron spectroscopy and was used as a very efficient catalyst in the Suzuki–Miyaura cross-coupling reaction of aryl bromides and chlorides with arylboronic acids in aqueous media. Design of experiments indicates that the use of 0.22 mol % of Pd, K2CO3 as the base, and aqueous ethanol are the best reaction conditions. The reactions of aryl bromides take place at room temperature, and aryl chlorides react at 80 °C. The easily synthesized and air-stable catalyst Pd@C-dots@Fe3O4 NPs could be separated from the reaction mixture by using an external magnet and reused in eight consecutive runs with no significant loss of catalytic activity.The authors are grateful to the Institute for Advanced Studies in Basic Sciences (IASBS) and the Iran National Science Foundation (INSF-Grant number of 94010666) for support of this work. C.N. is grateful to the Spanish Ministerio de Economia y Competitividad (MINECO) (projects CTQ2013-43446-P and CTQ2014-51912-REDC), FEDER, the Generalitat Valenciana (PROMETEOII/2014/017), and the University of Alicante for financial support

Recyclable glucose-derived palladium(0) nanoparticles as in situ-formed catalysts for cross-coupling reactions in aqueous media

In situ-generated, glucose-derived palladium(0) nanoparticles were shown to be convenient and effective catalysts for aqueous Mizoroki-Heck, Sonogashira and Suzuki-Miyaura cross-coupling reactions. The addition of only 4-10 mol glucose to the reaction mixture lead to a significant increase in yield of the desired products in comparison to processes that omitted the renewable sugar. Interestingly, the Mizoroki-Heck reaction was observed to proceed in good yield even as the reaction reached acidic pH levels. Extensive analysis of the size and morphology of the in situ-formed palladium nanoparticles using advanced analytical techniques showed that the zero valent metal was surrounded by hydrophilic hydroxyl groups. The increased aqueous phase affinity afforded by these groups allowed for facile recycling of the catalyst

Catalytic nanosponges of acidic aluminosilicates for plastic degradation and CO2 to fuel conversion

The synthesis of solid acids with strong zeolite-like acidity and textural properties like amorphous aluminosilicates (ASAs) is still a challenge. In this work, we report the synthesis of amorphous “acidic aluminosilicates (AAS)”, which possesses Brønsted acidic sites like in zeolites and textural properties like ASAs. AAS catalyzes different reactions (styrene oxide ring-opening, vesidryl synthesis, Friedel−Crafts alkylation, jasminaldehyde synthesis, m-xylene isomerization, and cumene cracking) with better performance than state-of-the-art zeolites and amorphous aluminosilicates. Notably, AAS efficiently converts a range of waste plastics to hydrocarbons at significantly lower temperatures. A Cu-Zn-Al/AAS hybrid shows excellent performance for CO2 to fuel conversion with 79% selectivity for dimethyl ether. Conventional and DNP-enhanced solid-state NMR provides a molecular-level understanding of the distinctive Brønsted acidic sites of these materials. Due to their unique combination of strong acidity and accessibility, AAS will be a potential alternative to zeolites

Regio- and stereoselective microwave-assisted synthesis of 5-alkyl-4-alkenyl-4-phenyl-1,3-oxazolidin-2-ones

Chiral symmetrical alk-2-yne-1,4-diols have been stereoselectively transformed into 5-alkyl-4-alkenyl-4-phenyl-1,3-oxazolidin- 2-ones, which are precursors of quaternary α-amino β-hydroxy acids. The key step was the cyclization of the bis(tosylcarbamates) of 2- phenylalk-2-yne-1,4-diols, easily obtained from the starting chiral diols. These cyclizations were accomplished with complete regioselectivity and up to 92:8 dr in the presence of catalytic amounts of Ni(0) or Pd (II) derivatives under microwave heating

Rhodium-NHC hybrid silica materials as recyclable catalysts for [2+2+2] cycloaddition reactions of alkynes

Bis-silylated dihydroimidazolium salt 1 and monosilylated imidazolium salt 2 are transformed to (NHC)RhCl(COD) complexes 3 and 4, allowing the preparation of hybrid silica materials either by sol-gel or grafting processes. Full characterization of the materials by means of solid state NMR, N₂-sorption measurements, thermogravimetric analysis (TGA) and elemental analysis was followed by evaluation of catalytic activity in the [2+2+2] cycloaddition of alkynes. Excellent yields of the cycloadducts are obtained for up to six consecutive cycles with the grafted material, using simple filtration to recover the catalyst. Both conventional and microwave heating prove effective for the process described

A SENSITIVE SPECTROPHOTOMETRIC DETERMINATION OF CENTBUCRIDINE HYDROCHLORIDE IN BULK DRUG & PHAMACEUTICAL FORMULATIONS

A new, simple, sensitive Spectrophotometric method in ultraviolet region has been developed for the determination of Centbucridine hydrochloride in bulk and in dosage form. Centbucridine Hydrochloride shows maximum absorbance at 247 nm with apparent molar absorptivity of 1.0781 X 104 l/mol.cm. Beers law was obeyed in the concentration range of 5 to 50 µg/ml. Results of analysis were validated statistically and by recovery studies. The developed method was found to be sensitive, accurate, precise and reproducible and can be used for the routine quality control analysis of Centbucridine

Supported palladium nanoparticles as heterogeneous ligand-free catalysts for the Hiyama C C coupling of vinylsilanes and halobenzenes leading to styrenes

[EN] Palladium nanoparticles supported on magnesia is a highly efficient solid, reusable catalyst to promote in the absence of phosphine ligands the coupling of vinylsilanes with iodo- and bromobenzenes to form styrenes.Financial support by Spanish Ministry of Science and Innovation (Consolider MULTICAT and CTQ 2012-32316) is gratefully acknowledged. The Generalidad Valenciana is also thanked for partial financial support (Prometeo Grant).Grirrane, A.; García Gómez, H.; Corma Canós, A. (2013). Supported palladium nanoparticles as heterogeneous ligand-free catalysts for the Hiyama C C coupling of vinylsilanes and halobenzenes leading to styrenes. Journal of Catalysis. 302:49-57. doi:10.1016/j.jcat.2013.02.019S495730

2,9-Dichloro-6H,13H-5:12,7:14-di­methano­dibenzo[d,i][1,3,6,8]tetra­azecine

The title compound, C16H14Cl2N4, is isomorphous with 2,9-dimethyl-6H,13H-5:12,7:14-dimethano­dibenzo[d,i]-[1,3,6,8]tetra­azecine [Rivera et al. (2009 ▶). Acta Cryst. E65, o2553] and has twofold symmetry, with two carbon atoms located on a twofold axis. Only van der Waals forces occur between molecules in the crystal. In the isomorphous compound the crystal structure is stabilized by weak C—H⋯π inter­actions