1,721,098 research outputs found
REGIOSELECTIVE HYDROGENATION OF 3-PHENYLPROPENAL AND OF TRANS-2-HEXENAL TO SATURATED ALDEHYDES CATALYZED BY ULTRAFINE RHODIUM PARTICLES DISPERSED ON ACRYLIC RESINS
No full textSynthesis and homopolymerization of [bis(2-acetylacetoxy-ethylmethacrylate) copper(II)].
No full textAerobic oxidations of unsaturated substrates under mukaiyama's conditions: The role of the metal and of the sacrificial aldehyde
No full textAerobic epoxidation of unsaturated substrates has been achieved under Mukaiyama's conditions (atmospheric pressure of dioxygen, in the presence of an excess of sacrificial aldehyde) with or without metal catalyst. The influence of light in non-catalysed reactions and the possible role of the aldehyde and of the metal complex in catalysed reactions are discussed. Two mechanistic pathways are proposed for Co(II) and Fe(III) [Ni(II)] catalytic centres
AEROBIC EPOXIDATION OF HINDERED OLEFINS AND ENOL ETHERS CATALYZED BY A POLYMERIZABLE B-KETOESTERATE COMPLEX OF IRON(III)
No full textPeculiar hindered olefins and derivatives have been epoxidized, under Mukaiyama's conditions, using iron(III) catalytic centres. The experimental results allow to rule out the involvement of singlet oxygen and free peroxyacids as active species
Remote meta-selective C-H bromination of arenes using a recyclable Ru-based aminopropyl bifunctional PMO with robust imidazolium bridges
No full textThis systematic study delves into the synthesis and characterization of robust bi-functional aminopropyl-tagged periodic mesoporous organosilica with a high loading of small imidazolium bridges in its framework (PrNH2@R-PMO-IL, ∼2 mmol g−1 of IL). The materials proved to be a reliable and enduring support for the immobilization of Ru species, demonstrating strong performance and excellent selectivity in the meta-bromination of various derivatives of 2-phenylpyridine compounds and other heterocycles, showcasing its effectiveness and robust nature. The synthesized materials were thoroughly characterized to determine their structural properties, such as pore size distribution, loading of organic groups, and surface area, using various analytical techniques. The research aims to improve the catalytic activity of supported ruthenium species in meta-selective bromination reactions through a systematic approach that emphasizes the synergistic effects of the mesoporous structure, concentration of imidazolium incorporated, and aminopropyl functionalization for enhancing the catalytic performance of the supported Ru species in these reactions. Our findings indicate that the developed catalyst system exhibits promise as a recyclable catalyst for meta-C-H activation, offering the potential for multiple reaction cycles and reduced waste production. This study highlights the enhanced catalytic performance and versatility of Ru@PrNH2@R-PMO-IL in comparison with previously documented homogeneous and heterogeneous catalyst systems, even when using lower loading levels. This is particularly evident in meta-C-H bromination of challenging substrates, such as 1-phenylpyrazole for the first time under the described catalytic chemical reaction
VSI in memory of Prof. Rosario Pietropaolo (1941–2022): the man, the scientist, and the enlightened founder
No full textUncovering Intramolecular π-Type Hydrogen Bonds in Solution by NMR Spectroscopy and DFT Calculations
No full textReaction between the phosphinito bridged diplatinum species [(PHCy2)Pt(μ-PCy2){κ2P,O-μ-P(O)Cy2}Pt(PHCy2)](Pt-Pt) (1), and (trimethylsilyl)acetylene at 273 K affords the σ-acetylide complex [(PHCy2)(η1-Me3SiC≡C)Pt(μ-PCy2)Pt(PHCy2){κP-P(OH)Cy2}](Pt-Pt) (2) featuring an intramolecular π-type hydrogen bond. Scalar and dipolar couplings involving the POH proton were detected by 2D NMR experiments. Relativistic DFT calculations of the geometry, relative energy, and NMR properties of model systems of 2 confirmed the structural assignment and allowed the energy of the π-type hydrogen bond to be estimated (ca. 22 kJ mol-1). Hydrogen bonds in solution: The existence of a π-type hydrogen bond between the PO-H and the C≡C triple bond in the σ-acetylide complex [(PHCy2)(η1-Me3SiC≡C)Pt(μ-PCy2)Pt(PHCy2){κP-P(OH)Cy2}](Pt-Pt) (2) in solution was proven by multinuclear NMR spectroscopy and confirmed by relativistic DFT calculations on model systems of 2. The estimated hydrogen-bonding energy and the calculated coupling values and chemical shift indicate a remarkably strong π-type interaction (see scheme)
Enantioselective C-C-Linkages by telomerization of butadiene
No full textThe substrates such as aldehydes, nitroalkanes, enamines and beta-dicarbonyl compounds were used to obtain the optically active octadienyl compounds in a high yield by means of palladium catalysis
Catalytic Pauson-Khand reactions in ionic liquids
No full textIonic liquids (ILs) are suitable media for the Co-2(CO)(8)-catalysed intramolecular and intermolecular Pauson-Khand (PK) annelation, provided that the reaction is carried out under a CO pressure of 10 bar. Two diethyl allyl propargyl malonates were quantitatively converted into the relevant cyclopentenones, whereas heteroatom tethered enynes gave lower yields in their cyclocarbortylation products. A moderate yield in the corresponding Pauson-Khand product was obtained reacting phenylacetylene with norbornene
Hydrogenation of Ethyl 12-Trimethylsilyl-9-dodecyn-11-enoate by Isocyanide Polymer Rh(PPh3)3Cl
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