Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Asymmetric Lewis acid catalysis directed by octahedral rhodium centrochirality.

ABSTRACT: A rhodium-based asymmetric catalyst is introduced which derives its optical activity from octahedral centrochirality. Besides providing the exclusive source of chirality, the rhodium center serves as a Lewis acid by activating 2-acyl imidazoles through two point binding and enabling a very effective asymmetric induction mediated by the propeller-like C2-symmetrical ligand sphere. Applications to asymmetric Michael additions (electrophile activation) as well as asymmetric ?-aminations (nucleophile activation) are disclosed, for which the rhodium catalyst is found to be overall superior to its iridium congener. Due to its straightforward proline-mediated synthesis, high catalytic activity (catalyst loadings down to 0.1 mol%), and tolerance towards moisture and air, this novel class of chiral-at-rhodium catalysts will likely to become of widespread use as chiral Lewis acid catalysts for a large variety of asymmetric transformations.

SUBMITTER: Wang C

PROVIDER: S-EPMC5811158 | biostudies-literature | 2015 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Asymmetric Lewis acid catalysis directed by octahedral rhodium centrochirality.

Wang Chuanyong C Chen Liang-An LA Huo Haohua H Shen Xiaodong X Harms Klaus K Gong Lei L Meggers Eric E

Chemical science 20141110 2

A rhodium-based asymmetric catalyst is introduced which derives its optical activity from octahedral centrochirality. Besides providing the exclusive source of chirality, the rhodium center serves as a Lewis acid by activating 2-acyl imidazoles through two point binding and enabling a very effective asymmetric induction mediated by the propeller-like <i>C</i><sub>2</sub>-symmetrical ligand sphere. Applications to asymmetric Michael additions (electrophile activation) as well as asymmetric α-amin ...[more]

PMID: 29560197

Similar Datasets

Lewis acid enhancement by hydrogen-bond donors for asymmetric catalysis.

Project description:Small-molecule dual hydrogen-bond (H-bond) donors such as ureas, thioureas, squaramides, and guanidinium ions enjoy widespread use as effective catalysts for promoting a variety of enantioselective reactions. However, these catalysts are only weakly acidic and therefore require highly reactive electrophilic substrates to be effective. We introduce here a mode of catalytic activity with chiral H-bond donors that enables enantioselective reactions of relatively unreactive electrophiles. Squaramides are shown to interact with silyl triflates by binding the triflate counterion to form a stable, yet highly Lewis acidic, complex. The silyl triflate-chiral squaramide combination promotes the generation of oxocarbenium intermediates from acetal substrates at low temperatures. Enantioselectivity in nucleophile additions to the cationic intermediates is then controlled through a network of noncovalent interactions between the squaramide catalyst and the oxocarbenium triflate.

| S-EPMC5728151 | biostudies-literature

Asymmetric counteranion-directed Lewis acid organocatalysis for the scalable cyanosilylation of aldehydes.

Project description:Due to the high versatility of chiral cyanohydrins, the catalytic asymmetric cyanation reaction of carbonyl compounds has attracted widespread interest. However, efficient protocols that function at a preparative scale with low catalyst loading are still rare. Here, asymmetric counteranion-directed Lewis acid organocatalysis proves to be remarkably successful in addressing this problem and enabled a molar-scale cyanosilylation in quantitative yield and with excellent enantioselectivity. Also, the catalyst loading could be lowered to a part-per-million level (50?ppm: 0.005?mol%). A readily accessible chiral disulfonimide was used, which in combination with trimethylsilyl cyanide, turned into the active silylium Lewis acid organocatalyst. The nature of a peculiar phenomenon referred to as a "dormant period", which is mainly induced by water, was systematically investigated by means of in situ Fourier transform infrared analysis.

| S-EPMC4992067 | biostudies-literature

Asymmetric synthesis of diamine derivatives via sequential palladium and rhodium catalysis.

Project description:The use of a bifunctional nitrogen nucleophile and an allyl carbonate starting material in successive enantioselective palladium- and diastereoselective rhodium-catalyzed reactions enables the rapid assembly of unique amino aziridine products. Further elaboration of these materials affords complex, stereodefined polyamine architectures, thus demonstrating the power of these combined methods for simplifying asymmetric C-N bond construction.

| S-EPMC3235049 | biostudies-literature

Asymmetric Full Saturation of Vinylarenes with Cooperative Homogeneous and Heterogeneous Rhodium Catalysis.

Project description:Homogeneous and heterogeneous catalyzed reactions can seldom operate synergistically under the same conditions. Here we communicate the use of a single rhodium precursor that acts in both the homogeneous and heterogeneous phases for the asymmetric full saturation of vinylarenes that, to date, constitute an unmet bottleneck in the field. A simple asymmetric hydrogenation of a styrenic olefin, enabled by a ligand accelerated effect, accounted for the facial selectivity in the consecutive arene hydrogenation. Tuning the ratio between the phosphine ligand and the rhodium precursor controlled the formation of homogeneous and heterogeneous catalytic species that operate without interference from each other. The system is flexible in terms of both the chiral ligand and the nature of the external olefin. We anticipate that our findings will promote the development of asymmetric arene hydrogenations.

| S-EPMC8662739 | biostudies-literature

The Intermediates in Lewis Acid Catalysis with Lanthanide Triflates.

Project description:Lanthanide triflates are effective Lewis acid catalysts in reactions involving carbonyl compounds due to their high oxophilicity and water stability. Despite the growing interest, the identity of the catalytic species formed in lanthanide catalysed reactions is still unknown. We have therefore used mass spectrometry and ion spectroscopy to intercept and characterize the intermediates in a reaction catalysed by ytterbium and dysprosium triflates. We were able to identify a number of lanthanide intermediates formed in a simple condensation reaction between a C-acid and an aldehyde. Results show correlation between the reactivity of lanthanide complexes and their charge state and suggest that the triply charged complexes play a key role in lanthanide catalysed reactions. Spectroscopic data of the gaseous ions accompanied by theoretical calculations reveal that the difference between catalytic efficiencies of ytterbium and dysprosium ions can be explained by their different electrophilicity.

| S-EPMC6813638 | biostudies-literature

A Highly Lewis Acidic Strontium ansa-Arene Complex for Lewis Acid Catalysis and Isobutylene Polymerization.

Project description:The potential of a dicationic strontium ansa-arene complex for Lewis acid catalysis has been explored. The key to its synthesis was a simple salt metathesis from SrI2 and 2 Ag[Al(ORF )4 ], giving the base-free strontium-perfluoroalkoxyaluminate Sr[Al(ORF )4 ]2 (ORF =OC(CF3 )3 ). Addition of an ansa-arene yielded the highly Lewis acidic, dicationic strontium ansa-arene complex. In preliminary experiments, the complex was successfully applied as a catalyst in CO2 -reduction to CH4 and a surprisingly controlled isobutylene polymerization reaction.

| S-EPMC7756322 | biostudies-literature

Enantioselective bromocycloetherification by Lewis base/chiral Bronsted acid cooperative catalysis.

Project description:A binary catalyst system for the enantioselective bromocycloetherification of 5-arylpentenols is described. The combination of an achiral Lewis base and a chiral Brønsted acid affords good enantioselectivities for the cyclization of Z configured 5-arylpentenols to form bromomethyltetrahydrofurans. The constitutional site selectivity is highly dependent upon the aromatic substituent and the configuration of the double bond.

| S-EPMC3238797 | biostudies-literature

Lewis Acid Enabled Copper-Catalyzed Asymmetric Synthesis of Chiral ?-Substituted Amides.

Project description:Here we report that readily available silyl- and boron-based Lewis acids in combination with chiral copper catalysts are able to overcome the reactivity issues of unactivated enamides, known as the least reactive carboxylic acid derivatives, toward alkylation with organomagnesium reagents. Allowing unequaled chemo-reactivity and stereocontrol in catalytic asymmetric conjugate addition to enamides, the method is distinguished by its unprecedented reaction scope, allowing even the most challenging and synthetically important methylations to be accomplished with good yields and excellent enantioselectivities. This catalytic protocol tolerates a broad temperature range (-78 °C to ambient) and scale up (10 g), while the chiral catalyst can be reused without affecting overall efficiency. Mechanistic studies revealed the fate of the Lewis acid in each elementary step of the copper-catalyzed conjugate addition of Grignard reagents to enamides, allowing us to identify the most likely catalytic cycle of the reaction.

| S-EPMC5639465 | biostudies-literature

Sixteen isostructural phosphonate metal-organic frameworks with controlled Lewis acidity and chemical stability for asymmetric catalysis.

Project description:Heterogeneous catalysts typically lack the specific steric control and rational electronic tuning required for precise asymmetric catalysis. Here we demonstrate that a phosphonate metal-organic framework (MOF) platform that is robust enough to accommodate up to 16 different metal clusters, allowing for systematic tuning of Lewis acidity, catalytic activity and enantioselectivity. A total of 16 chiral porous MOFs, with the framework formula [M3 L 2(solvent)2] that have the same channel structures but different surface-isolated Lewis acid metal sites, are prepared from a single phosphono-carboxylate ligand of 1,1'-biphenol and 16 different metal ions. The phosphonate MOFs possessing tert-butyl-coated channels exhibited high thermal stability and good tolerances to boiling water, weak acid and base. The MOFs provide a versatile family of heterogeneous catalysts for asymmetric allylboration, propargylation, Friedel-Crafts alkylation and sulfoxidation with good to high enantioselectivity. In contrast, the homogeneous catalyst systems cannot catalyze the test reactions enantioselectively.

| S-EPMC5736719 | biostudies-literature

Enantiodivergent [4+2] Cycloaddition of Dienolates by Polyfunctional Lewis Acid/Zwitterion Catalysis.

Project description:Diels-Alder reactions have become established as one of the most effective ways to prepare stereochemically complex six-membered rings. Different catalysis concepts have been reported, including dienophile activation by Lewis acids or H-bond donors and diene activation by bases. Herein we report a new concept, in which an acidic prodiene is acidified by a Lewis acid to facilitate deprotonation by an imidazolium-aryloxide entity within a polyfunctional catalyst. A metal dienolate is thus formed, while an imidazolium-ArOH moiety probably forms hydrogen bonds with the dienophile. The catalyst type, readily prepared in few steps in high overall yield, was applied to 3-hydroxy-2-pyrone and 3-hydroxy-2-pyridone as well as cyclopentenone prodienes. Maleimide, maleic anhydride, and nitroolefin dienophiles were employed. Kinetic, spectroscopic, and control experiments support a cooperative mode of action. High enantioselectivity was observed even with unprecedented TONs of up to 3680.

| S-EPMC7693193 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

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