Search results for "Catàlisi"
showing 10 items of 61 documents
Enantioselective Synthesis of 2-Amino-1,1-diarylalkanes Bearing a Carbocyclic Ring Substituted Indole through Asymmetric Catalytic Reaction of Hydrox…
2018
[EN] An asymmetric catalytic reaction of hydroxyindoles with nitroalkenes leading to the Friedel-Crafts alkylation in the carbocyclic ring of indole is presented. The method is based on the activating/directing effects of the hydroxy group situated in the carbocyclic ring of the indole providing nitroalkylated indoles functionalizated at the C-4, C-5, and C-7 positions with high yield, regio-, and enantioselectivity. The optically enriched nitroalkanes were transformed efficiently in optically enriched 2-amino-1,1-diarylalkanes bearing a carbocyclic ring substituted indole.
Organocatalytic Enantioselective Synthesis of α-Hydroxyketones through a Friedel−Crafts Reaction of Naphthols and Activated Phenols with Aryl- and Al…
2016
[EN] An efficient organocatalytic asymmetric synthesis of alpha-hydroxyketones has been developed. Quinine-derived thiourea catalyzed the enantioselective Friedel Crafts alkylation of naphthols and activated phenols with aryl- and alkylglyoxal hydrates, providing the corresponding chiral alpha-hydroxyketones with high yields (up to 97%) and excellent enantioselectivities (up to 99% ee).
Organocatalytic Enantioselective Synthesis of Pyrazoles Bearing a Quaternary Stereocenter
2016
An efficient one-pot asymmetric synthesis of pyrazoles bearing a chiral quaternary stereocenter has been developed. Quinine-derived thiourea catalyzed the enantioselective addition of pyrazolones to isatin-derived ketimines, providing the corresponding acetylated pyrazoles after in situ treatment with Ac2O/Et3N. The corresponding pyrazoles were afforded in high yields and excellent enantioselectivities.
Catalytic Diastereo- and enantioselective vinylogous Mannich reaction of alkylidenepyrazolones to isatin-derived ketimines
2021
A valuable organocatalytic vinylogous Mannich reaction between alkylidenepyrazolones and isatin-derived ketimines has been successfully established. Squaramide organocatalyst, prepared from quinine, catalyzed the diastereo- and enantioselective vinylogous Mannich addition, affording a range of aminooxindole-pyrazolone adducts (24 examples) with excellent outcomes: up to 98% yield with complete diastereoselectivity and excellent enantioselectivity (up to 99% ee). Additionally, different synthetic transformations were performed with the chiral pyrazolone-oxindole adducts.
Crystallographic Visualization of a Double Water Molecule Addition on a Pt 1 ‐MOF during the Low‐temperature Water‐Gas Shift Reaction
2021
[EN] The low-temperature water-gas shift reaction (WGSR, CO+H2O H-2+CO2) is considered a very promising reaction -candidate for fuel cells- despite an efficient and robust catalyst is still desirable. One of the more prominent catalysts for this reaction is based on single Pt atoms (Pt-1) on different supports, which are supposed to manifold the reaction by the accepted mechanism for the general WGSR, i. e. by addition of one H2O molecule to CO, with generation of CO2 and H-2. Here we show, experimentally, that not one but two H2O molecules are added to CO on the Pt-1 catalyst, as assessed by a combination of reactivity experiments with soluble Pt catalysts, kinetic and spectroscopic measur…
MOF-Mediated Synthesis of Supported Fe-Doped Pd Nanoparticles under Mild Conditions for Magnetically Recoverable Catalysis**
2020
Metal–organic framework (MOF)-driven synthesis is considered as a promising alternative for the development of new catalytic materials with well-designed active sites. This synthetic approach is used here to gradually transform a new bimetallic MOF, with Pd and Fe as the metal components, by the in situ generation of aniline under mild conditions. This methodology results in a compositionally homogeneous nanocomposite formed by Fe-doped Pd nanoparticles that, in turn, are supported on iron oxide-doped carbon. The nanocomposite has been fully characterized by several techniques such as IR and Raman spectroscopy, TEM, XPS, and XAS. The performance of this nanocomposite as an heterogeneous cat…
Catalytic Enantioselective Cyclopropylalkynylation of Aldimines Generated In Situ from α-Amido Sulfones
2022
A convenient procedure of synthesis of N-carbamoyl-protected propargylic amines substituted with a cyclopropyl group from α-amido sulfones and cyclopropylacetylene is described. The reaction is catalyzed by a chiral BINOL-type zinc complex and provides the corresponding products in good yields and enantioselectivities.
Organocatalytic Enantioselective Alkylation of Pyrazol-3-ones with Isatin-Derived Ketimines: Stereocontrolled Construction of Vicinal Tetrasubstitute…
2016
A quinine-derived thiourea catalysed the enantioselective addition of 4-substituted pyrazolones to isatin-derived ketimines, providing a variety of aminooxindole-pyrazolone adducts containing congested vicinal tetrasubstituted stereocentres with excellent outcomes (up to 98% yield, >20:1 dr and 98% ee).
Bimetallic Intersection in PdFe@FeO x ‐C Nanomaterial for Enhanced Water Splitting Electrocatalysis
2022
Supported Fe-doped Pd-nanoparticles (NPs) are prepared via soft transformation of a PdFe-metal oraganic framework (MOF). The thus synthesized bimetallic PdFe-NPs are supported on FeO@C layers, which are essential for developing well-defined and distributed small NPs, 2.3 nm with 35% metal loading. They are used as bifunctional nanocatalysts for the electrocatalytic water splitting process. They display superior mass activity for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), both in alkaline and acid media, compared with those obtained for benchmarking platinum HER catalyst, and ruthenium, and iridium oxide OER catalysts. PdFe-NPs also exhibit outstanding sta…
Few-layer Black Phosphorous Catalyzes Radical Additions to Alkenes Faster than Low-valence Metals
2020
Abstract The substitution of catalytic metals by p‐block main elements has a tremendous impact not only in the fundamentals but also in the economic and ecological fingerprint of organic reactions. Here we show that few‐layer black phosphorous (FL‐BP), a recently discovered and now readily available 2D material, catalyzes different radical additions to alkenes with an initial turnover frequency (TOF0) up to two orders of magnitude higher than representative state‐of‐the‐art metal complex catalysts at room temperature. The corresponding electron‐rich BP intercalation compound (BPIC) KP6 shows a nearly twice TOF0 increase with respect to FL‐BP. This increase in catalytic activity respect to t…