Browse
Submit Data
Databases
API
Help

Dataset Information

7 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Silylated cyclopentadienes as competent silicon Lewis acid catalysts.

ABSTRACT: The synthesis and characterization of silicon Lewis acid complexes that incorporate highly electron-deficient cyclopentadienes is reported. Several pentacarboxycyclopentadienyl and monocarboxytetracyanocyclopentadienyl complexes were prepared. A comparison of their reactivities for catalysis of the allylation of an electron-deficient benzaldehyde was established. The use of a monocarboxytetracyano silylium donor was shown to be effective for the allylation or arylation of a variety of electrophiles via an anion abstraction pathway.

SUBMITTER: Radtke MA

PROVIDER: S-EPMC6115689 | biostudies-other | 2018 Aug

REPOSITORIES: biostudies-other

ACCESS DATA

Json Xml

Publications

Silylated cyclopentadienes as competent silicon Lewis acid catalysts.

Radtke M Alex MA Lambert Tristan H TH

Chemical science 20180629 30

The synthesis and characterization of silicon Lewis acid complexes that incorporate highly electron-deficient cyclopentadienes is reported. Several pentacarboxycyclopentadienyl and monocarboxytetracyanocyclopentadienyl complexes were prepared. A comparison of their reactivities for catalysis of the allylation of an electron-deficient benzaldehyde was established. The use of a monocarboxytetracyano silylium donor was shown to be effective for the allylation or arylation of a variety of electrophi ...[more]

PMID: 30310569

Similar Datasets

Electrophilic bis-fluorophosphonium dications: Lewis acid catalysts from diphosphines.

Project description:Stepwise oxidation of 1,8-bis(diphenylphosphino)naphthalene and a series of (oligo)methylene-linked diphosphines with XeF2 followed by fluoride abstraction yields a family of compounds featuring phosphine, phosphonium and phosphorane moieties in close proximity. The bisphosphonium ions [(C10H6)(Ph2PF)2]2+ (5) and [CH2(Ph2PF)2]2+ (9a) exhibit remarkable Lewis acidity arising from the proximity of the phosphonium centers. The effectiveness of bisphosphonium dications (5, 9a-e) is examined in a series of Lewis acid catalysed transformations.

| S-EPMC5496503 | biostudies-literature

Iron catalyzed CO2 hydrogenation to formate enhanced by Lewis acid co-catalysts.

Project description:A family of iron(ii) carbonyl hydride complexes supported by either a bifunctional PNP ligand containing a secondary amine, or a PNP ligand with a tertiary amine that prevents metal-ligand cooperativity, were found to promote the catalytic hydrogenation of CO2 to formate in the presence of Brønsted base. In both cases a remarkable enhancement in catalytic activity was observed upon the addition of Lewis acid (LA) co-catalysts. For the secondary amine supported system, turnover numbers of approximately 9000 for formate production were achieved, while for catalysts supported by the tertiary amine ligand, nearly 60?000 turnovers were observed; the highest activity reported for an earth abundant catalyst to date. The LA co-catalysts raise the turnover number by more than an order of magnitude in each case. In the secondary amine system, mechanistic investigations implicated the LA in disrupting an intramolecular hydrogen bond between the PNP ligand N-H moiety and the carbonyl oxygen of a formate ligand in the catalytic resting state. This destabilization of the iron-bound formate accelerates product extrusion, the rate-limiting step in catalysis. In systems supported by ligands with the tertiary amine, it was demonstrated that the LA enhancement originates from cation assisted substitution of formate for dihydrogen during the slow step in catalysis.

| S-EPMC5707511 | biostudies-literature

Protecting-Group-Free Amidation of Amino Acids using Lewis Acid Catalysts.

Project description:Amidation of unprotected amino acids has been investigated using a variety of 'classical" coupling reagents, stoichiometric or catalytic group(IV) metal salts, and boron Lewis acids. The scope of the reaction was explored through the attempted synthesis of amides derived from twenty natural, and several unnatural, amino acids, as well as a wide selection of primary and secondary amines. The study also examines the synthesis of medicinally relevant compounds, and the scalability of this direct amidation approach. Finally, we provide insight into the chemoselectivity observed in these reactions.

| S-EPMC5969221 | biostudies-other

Catalytic preparation of levulinic acid from cellobiose via Bronsted-Lewis acidic ionic liquids functional catalysts.

Project description:Brønsted-Lewis acidic ionic liquids (ILs) were applied to catalyze cellobiose to prepare levulinic acid (LA) in one pot under hydrothermal conditions. Under the optimum conditions, the highest LA yield of 67.51% was obtained when low [HO3S-(CH2)3-mim]Cl-FeCl3 (molar fraction of FeCl3 x?=?0.60) was used. This indicated the Brønsted-Lewis acidic ILs played an active role in the conversion of cellobiose to LA. The catalytic mechanism of ILs had been established, disclosing that the Brønsted-Lewis acidic ILs had the catalytic synergistic effect originating from its double acid sites. During the reaction process, the Lewis acid sites improved the isomerization of glucose to fructose, then the Brønsted and Lewis acid sites simultaneously enhanced the dehydration of fructose to produce hydroxymethylfurfural (HMF), which was propitious to the synthesize LA with high yield. In addition, LA could be easily extracted by methyl isobutyl ketone (MIBK), and the ILs could retain its basic activity after 5 cycles. The solid residues were characterized using SEM, FT-IR and TG-DTG spectroscopy. It was the conclusion that a large amount of humins were produced during the cellobiose conversion process. In this reaction, the ILs not only overcomes the problems of the conventional catalyst, but also completes the reaction-separation integration and the recycling of the catalyst. This paper provided an important theoretical basis for the application of ILs in the field of biomass.

| S-EPMC6372595 | biostudies-literature

Atomically dispersed Lewis acid sites boost 2-electron oxygen reduction activity of carbon-based catalysts.

Project description:Elucidating the structure-property relationship is crucial for the design of advanced electrocatalysts towards the production of hydrogen peroxide (H2O2). In this work, we theoretically and experimentally discovered that atomically dispersed Lewis acid sites (octahedral M-O species, M = aluminum (Al), gallium (Ga)) regulate the electronic structure of adjacent carbon catalyst sites. Density functional theory calculation predicts that the octahedral M-O with strong Lewis acidity regulates the electronic distribution of the adjacent carbon site and thus optimizes the adsorption and desorption strength of reaction intermediate (*OOH). Experimentally, the optimal catalyst (oxygen-rich carbon with atomically dispersed Al, denoted as O-C(Al)) with the strongest Lewis acidity exhibited excellent onset potential (0.822 and 0.526 V versus reversible hydrogen electrode at 0.1 mA cm-2 H2O2 current in alkaline and neutral media, respectively) and high H2O2 selectivity over a wide voltage range. This study provides a highly efficient and low-cost electrocatalyst for electrochemical H2O2 production.

| S-EPMC7603490 | biostudies-literature

Isolable Silicon-Based Polycations with Lewis Superacidity.

Project description:Molecular silicon polycations of the types R2 Si2+ and RSi3+ (R=H, organic groups) are elusive Lewis superacids and currently unknown in the condensed phase. Here, we report the synthesis of a series of isolable terpyridine-stabilized R2 Si2+ and RSi3+ complexes, [R2 Si(terpy)]2+ (R=Ph 12+ ; R2 =C12 H8 22+ , (CH2 )3 32+ ) and [RSi(terpy)]3+ (R=Ph 43+ , cyclohexyl 53+ , m-xylyl 63+ ), in form of their triflate salts. The stabilization of the latter is achieved through higher coordination and to the expense of reduced fluoride-ion affinities, but a significant level of Lewis superacidity is nonetheless retained as verified by theory and experiment. The complexes activate C(sp3 )-F bonds, as showcased by stoichiometric fluoride abstraction from 1-fluoroadamantane (AdF) and the catalytic hydrodefluorination of AdF. The formation of the crystalline adducts [2(F)]+ and [5(H)]2+ documents in particular the high reactivity towards fluoride and hydride donors.

| S-EPMC7756528 | biostudies-literature

Design and reactions of a carbon Lewis base/boron Lewis acid frustrated Lewis pair.

Project description:The conjugated dienamine 4 selectively adds Piers' borane [HB(C6F5)2] to give the enamine/borane system 5, which features a boratirane structure by internal enamine carbon Lewis base to boron Lewis acid interaction. Compound 5 behaves as a C/B frustrated Lewis pair and undergoes typical addition reactions to benzaldehyde, several nitriles and to sulfur dioxide.This article is part of the themed issue 'Frustrated Lewis pair chemistry'.

| S-EPMC5540844 | biostudies-literature

Lewis Base Activation of Lewis Acid: A Detailed Bond Analysis.

Project description:The effect of a Lewis base (LB) on the nucleophilic attack on chalcogeniranium (chalcogen = sulfur and selenium) cations, the so-called LB activation of a Lewis acid, has been studied coupling natural orbital for chemical valence decomposition of the orbital interaction energy with charge displacement analysis. This methodology provides a detailed and accurate description of all the interactions (LB···chalcogen, chalcogen···olefin and olefin···ammonia) present in the system and leads to a deeper understanding of how they influence each other at all stages of the reaction: reactant complex, transition state, and product complex. In particular, the bond between the chalcogen and the olefin has been decomposed in terms of σ donation/π back-donation and the bond components quantified. This allowed determination of a linear relationship between the activation barrier of the nucleophilic attack and the net amount of charge donated by the olefin to the chalcogen.

| S-EPMC6643480 | biostudies-literature

Glycosylation of ?-amino acids by sugar acetate donors with InBr3. Minimally competent Lewis acids.

Project description:A simplified method for the preparation of Fmoc-serine and Fmoc-threonine glycosides for use in O-linked glycopeptide synthesis is described. Lewis acids promote glycoside formation, but also promote undesired reactions of the glycoside products. Use of 'minimally competent' Lewis acids such as InBr(3) promotes the desired activation catalytically, and with greatly reduced side products from sugar peracetates.

| S-EPMC3296895 | biostudies-literature

Localized photodeposition of catalysts using nanophotonic resonances in silicon photocathodes.

Project description:Nanostructured semiconductors feature resonant optical modes that confine light absorption in specific areas called "hot spots". These areas can be used for localized extraction of the photogenerated charges, which in turn could drive chemical reactions for synthesis of catalytic materials. In this work, we use these nanophotonic hot spots in vertical silicon nanowires to locally deposit platinum nanoparticles in a photo-electrochemical system. The tapering angle of the silicon nanowires as well as the excitation wavelength are used to control the location of the hot spots together with the deposition sites of the platinum catalyst. A combination of finite difference time domain (FDTD) simulations with scanning electron microscopy image analysis showed a reasonable correlation between the simulated hot spots and the actual experimental localization and quantity of platinum atoms. This nanophotonic approach of driving chemical reactions at the nanoscale using the optical properties of the photo-electrode, can be very promising for the design of lithography-free and efficient hierarchical nanostructures for the generation of solar fuels.

| S-EPMC6122171 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data