Search results for "Catalysis"

Reaction of 2,2′-bis(N-methylindolyl) with dimethyl acetylenedicarboxylate and thermally- and photochemically-induced cyclizations of the product

1995

2,2′-Bis(N-methylindolyl) 1 reacts with dimethyl acetylenedicarboxylate to furnish the 3-dimethyl maleoyl-substituted 2,2′-bisindolyl 2. Compound 2 cyclizes under aluminum trichloride catalysis according to a polar process to give a cyclopenta[2,1-b:3,4-b′]diindole derivative 4. Reaction of compound 4 with benzyl-amine yields the spiro derivative 5. Photochemically-induced 1,6-electrocyclization of compound 2 gives rise to the indolo[2,3-a]carbazole 6 directly, which is readily transformed to the pyrrolo-annelated carbazole 7 by treatment with benzylamine.

Catalytic Enantioselective Addition of Me2Zn to Isatins

2017

Chiral α-hydroxyamide L5 derived from (S)-(+)-mandelic acid catalyzes the enantioselective addition of dimethylzinc to isatins affording the corresponding chiral 3-hydroxy-3-methyl-2-oxindoles with good yields and er up to 90:10. Furthermore, several chemical transformations were performed with the 3-hydroxy-2-oxindoles obtained.

Novel supported dipeptides as recyclable catalysts for asymmetric aldol reaction

2009

A kinetic model for the oxidation of benzenethiol catalyzed by the [MoVIO2(O2CC(S)(C6H5)2)2]2− complex intercalated in a Zn(II)–Al(III) layered doubl…

2009

Abstract The heterogeneous oxidation of benzenethiol catalyzed by the dianionic bis(2-sulfanyl-2,2-diphenylethanoxycarbonyl) dioxomolybdate (VI) complex intercalated into a Zn(II)–Al(III) layered double hydroxide (LDH) host have been investigated under aerobic conditions. The kinetics of the system has been analysed in detail. In ethanol, the benzenethiol is cleanly oxidized to diphenyl disulfide in the acidic media provided by the protonic resin Amberlite IR-120(H). The reaction is second-order in benzenethiol, and the apparent rate coefficient has been found to be proportional to the catalyst weight and inversely proportional to the initial concentration of the substrate. A catalytic cycl…

Cyclocarbonylation reactions of allylphenols and allylnaphthols catalyzed by Pd/C- 1,4-bis(diphenylphosphine)butane

2002

Palladium/activated carbon (Pd/C) in the presence of 1,4-bis(diphenylphosphino)butane is an efficient heterogeneous catalyst for cyclocarbonylation reactions of 2-allyl phenols affording five-, six-, and seven-membered ring lactones. Various examples of cyclocarbonylation are reported and the regioselectivity is compared with the homogeneous system. Both commercial Pd/C and Pd/C prepared from activated carbons obtained from vegetable and polymeric wastes are investigated.

Bond stretching and redox behavior in coinage metal complexes of the dichalcogenide dianions [(SPh2P)2CEEC(PPh2S)2]2- (E=S, Se): diradical character …

2011

The metathetical reactions of a) [Li(tmeda)](2)[(S)C(PPh(2)S)(2)] (Li(2)·3c) with CuCl(2) and b) [Li(tmeda)](2)[(SPh(2)P)(2)CSSC(PPh(2)S)(2)] (Li(2)·4c) with two equivalents of CuCl both afford the binuclear Cu(I) complex {Cu(2)[(SPh(2)P)(2)CSSC(PPh(2)S)(2)]} (5c). The elongated (C)S-S(C) bond (ca. 2.54 and 2.72 A) of the dianionic ligand observed in the solid-state structure of 5c indicate the presence of diradical character as supported by theoretical analyses. The treatment of [Li(tmeda)](2)[(SPh(2)P)(2)CSeSeC(PPh(2)S)(2)] (Li(2)·4b) and Li(2)·4c with AgOSO(2)CF(3) produce the analogous Ag(I) derivatives, {Ag(2)[(SPh(2)P)(2)CEEC(PPh(2)S)(2)]} (6b, E=Se; 6c, E=S), respectively. The disele…

118 and Counting … The Periodic Table on its 150th Anniversary.

2019

"Is there still room for more elements in the modern periodic table with its currently 118 elements? Will we need another extra series in the periodic table besides the classical s-, p-, and d-block, and the lanthanides/actinides? Will the periodic table in this region still feature periodicity? …" Read more in the Guest Editorial by C. E. Dullmann.

Pd nanoparticles immobilized on the poly-dopamine decorated halloysite nanotubes hybridized with N-doped porous carbon monolayer: A versatile catalys…

2020

A hybrid catalyst, Pd@Hal-pDA-NPC, with the utility for promoting both C–C coupling reactions (Sonogashira, Heck and Suzuki reactions) and hydrogenation of nitrocompounds is prepared through two main steps. First, Pd(0) nanoparticles was immobilized on the poly-dopamine decorated halloysite nanotubes (Hal-pDA) and then Pd@Hal-pDA was hybridized with the layers of a novel multi-N-doped porous carbon monolayer derived from 4,4′,4″-((1,3,5-triazine-2,4,6-triyl)tris(azanediyl))tribenzonitrile. The results established that the catalyst could catalyze all the reactions efficiently under mild reaction condition. Moreover Pd@Hal-pDA-NPC exhibited high recyclability (up to ten reac…

Influence of a nano phase segregation on the thermoelectric properties of the p-type doped stannite compound Cu(2+x)Zn(1-x)GeSe4.

2012

Engineering nanostructure in bulk thermoelectric materials has recently been established as an effective approach to scatter phonons, reducing the phonon mean free path, without simultaneously decreasing the electron mean free path for an improvement of the performance of thermoelectric materials. Herein the synthesis, phase stability, and thermoelectric properties of the solid solutions Cu_(2+x)Zn_(1–x)GeSe_4 (x = 0–0.1) are reported. The substitution of Zn^(2+) with Cu^+ introduces holes as charge carriers in the system and results in an enhancement of the thermoelectric efficiency. Nano-sized impurities formed via phase segregation at higher dopant contents have been identified and are l…

Direct Methane Oxidation on La1-xSrxCr1-yFeyO3-δ perovskite-type oxides as Potential Anode for Intermediate Temperature Solid Oxide Fuel Cells

2016

Abstract La1−xSrxCr1−yFeyO3−δ (x = 0, 0.1, 0.15, 0.2; y = 0, 0.3, 0.5) perovskite-type oxide powders were synthesized by solution combustion synthesis and characterized by X-ray diffraction, X-ray photoelectron spectroscopy and H2-temperature programmed reduction. Selected compositions were studied by CH4-temperature programmed reduction in the absence and in the presence of H2S. Temperature programmed oxidation and structural characterizations were performed in order to discriminate the nature of residual deposits on the catalyst surface. The study about reduction in different methane-based mixture revealed that total and partial methane oxidation occurred in the range ∼450–1000 °C indepen…