Browse
Submit Data
Databases
API
Help

Dataset Information

20 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Asymmetric syntheses of three-membered heterocycles using chiral amide-based ammonium ylides.

ABSTRACT: The use of carbonyl-stabilised ammonium ylides to access chiral glycidic amides and the corresponding aziridines has so far been limited to racemic trans-selective protocols. We herein report the development of an asymmetric approach to access such compounds with high levels of stereoselectivity using easily accessible chiral auxiliary-based ammonium ylides. The use of phenylglycinol as the chiral auxiliary was found to be superior to Evans or pseudoephedrine-based auxiliaries resulting in good to excellent stereoselectivities in both, epoxidation and aziridination reactions.

SUBMITTER: Pichler M

PROVIDER: S-EPMC4323751 | biostudies-literature | 2015 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Asymmetric syntheses of three-membered heterocycles using chiral amide-based ammonium ylides.

Pichler Mathias M Novacek Johanna J Robiette Raphaël R Poscher Vanessa V Himmelsbach Markus M Monkowius Uwe U Müller Norbert N Waser Mario M

Organic & biomolecular chemistry 20150201 7

The use of carbonyl-stabilised ammonium ylides to access chiral glycidic amides and the corresponding aziridines has so far been limited to racemic trans-selective protocols. We herein report the development of an asymmetric approach to access such compounds with high levels of stereoselectivity using easily accessible chiral auxiliary-based ammonium ylides. The use of phenylglycinol as the chiral auxiliary was found to be superior to Evans or pseudoephedrine-based auxiliaries resulting in good ...[more]

PMID: 25521410

Similar Datasets

Enantioselective Spirocyclopropanation of para-Quinone Methides Using Ammonium Ylides.

Project description:The use of Cinchona alkaloid-based chiral ammonium ylides allows for the first highly enantioselective and broadly applicable spirocyclopropanation reactions of para-quinone methides. This strategy provides a straightforward protocol toward the chiral spiro[2.5]octa-4,7-dien-6-one skeleton, which is a frequently found structural motif in important biologically active molecules.

| S-EPMC5420312 | biostudies-literature

Syntheses and Applications of (Thio)Urea-Containing Chiral Quaternary Ammonium Salt Catalysts.

Project description:We herein report our efforts to obtain a new class of systematically modified bifunctional (thio)urea-containing quaternary ammonium salts based on easily obtainable chiral backbones. Among the different classes of catalysts that were successfully synthesized, those based on trans-1,2-cyclohexane diamine were found to be the most powerful for the asymmetric ?-fluorination of ?-keto esters. Selectivities up to 93:7 could be obtained by using only 2 mol-% of the optimized catalyst. The importance of the bifunctional nature of these catalysts was demonstrated by control experiments using simplified monofunctional catalyst analogues, which gave almost racemic product only.

| S-EPMC4202195 | biostudies-literature

Chiral ammonium betaine-catalyzed asymmetric Mannich-type reaction of oxindoles.

Project description:A highly diastereo- and enantioselective Mannich-type reaction of 3-aryloxindoles with N-Boc aldimines was achieved under the catalysis of axially chiral ammonium betaines. This catalytic method provides a new tool for the construction of consecutive quaternary and tertiary stereogenic carbon centers on biologically intriguing molecular frameworks with high fidelity.

| S-EPMC5082719 | biostudies-literature

Ring Enlargement of Three-Membered Heterocycles by Treatment with In Situ Formed Tricyanomethane.

Project description:Although the chemistry of elusive tricyanomethane (cyanoform) has been studied during a period of more than 150 years, this compound has very rarely been utilized in the synthesis or modification of heterocycles. Three-membered heterocycles, such as epoxides, thiirane, aziridines, or 2H-azirines, are now treated with tricyanomethane, which is generated in situ by heating azidomethylidene-malonodinitrile in tetrahydrofuran at 45 °C or by adding sulfuric acid to potassium tricyanomethanide. This leads to ring expansion with formation of 2-(dicyanomethylidene)oxazolidine derivatives or creation of the corresponding thiazolidine, imidazolidine, or imidazoline compounds and opens up a new access to these push-pull-substituted olefinic products. The regio- and stereochemistry of the ring-enlargement processes are discussed, and the proposed reaction mechanisms were confirmed by using 15 N-labeled substrates. It turns out that different mechanisms are operating; however, tricyanomethanide is always acting as a nitrogen-centered nucleophile, which is quite unusual if compared to other reactions of this species.

| S-EPMC7318174 | biostudies-literature

Asymmetric cycloadditions of o-quinone methides employing chiral ammonium fluoride precatalysts.

Project description:The catalytic, enantioselective, [4 + 2] cycloaddition reaction of ortho-quinone methides with silyl ketene acetals is described. This mechanistically interesting reaction, initiated by a chiral cinchona alkaloid-derived ammonium fluoride "precatalyst" complex, affords a variety of alkyl- and aryl-substituted 3,4-dihydrocoumarin products in excellent yield and with good enantioselectivity.

| S-EPMC2652256 | biostudies-literature

On the origin of the stereoselectivity in chiral amide-based ammonium ylide-mediated epoxidations.

Project description:AbstractDetailed DFT studies provide an in-depth mechanistic understanding for the use of chiral amide-based ammonium ylides in epoxidation reactions. It is shown that the used chiral auxiliary efficiently shields one face of the ylide, which thus results in an extraordinarily high stereoselectivity giving only one trans-isomer with perfect control of the absolute configuration.Graphical abstract

| S-EPMC5225234 | biostudies-literature

Asymmetric synthesis using chiral-encoded metal.

Project description:The synthesis of chiral compounds is of crucial importance in many areas of society and science, including medicine, biology, chemistry, biotechnology and agriculture. Thus, there is a fundamental interest in developing new approaches for the selective production of enantiomers. Here we report the use of mesoporous metal structures with encoded geometric chiral information for inducing asymmetry in the electrochemical synthesis of mandelic acid as a model molecule. The chiral-encoded mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and the chiral template molecule, perfectly retains the chiral information after removal of the template. Starting from a prochiral compound we demonstrate enantiomeric excess of the (R)-enantiomer when using (R)-imprinted electrodes and vice versa for the (S)-imprinted ones. Moreover, changing the amount of chiral cavities in the material allows tuning the enantioselectivity.

| S-EPMC5007459 | biostudies-literature

Reagent controlled addition of chiral sulfur ylides to chiral aldehydes.

Project description:The degree of reagent and substrate control in the reaction of chiral sulfur ylides with chiral aldehydes has been investigated. Specifically, the reactions of the two enantiomers of the chiral benzyl sulfonium salt 1 with glyceraldehyde acetonide were studied in detail. Of the two new stereogenic centers created, it was found that the C1 stereochemistry was largely controlled by the reagent, whereas control at the C2 center was dependent on the aldehyde used. In one case, the trans isomer was produced via reversible formation of the intermediate betaine, whereas in the alternative case, the C2 center was under Felkin Anh/Cornforth control through non-reversible formation of the betaine. Thus, the aldehyde stereocenter influenced the degree of reversibility in betaine formation, which impacted on the stereocontrol at the C2 position.

| S-EPMC1399452 | biostudies-literature

Phosphite mediated asymmetric N to C migration for the synthesis of chiral heterocycles from primary amines.

Project description:A phosphite mediated stereoretentive C-H alkylation of N-alkylpyridinium salts derived from chiral primary amines was achieved. The reaction proceeds through the activation of the N-alkylpyridinium salt substrate with a nucleophilic phosphite catalyst, followed by a base mediated [1,2] aza-Wittig rearrangement and subsequent catalyst dissociation for an overall N to C-2 alkyl migration. The scope and degree of stereoretention were studied, and both experimental and theoretical investigations were performed to support an unprecedented aza-Wittig rearrangement-rearomatization sequence. A catalytic enantioselective version starting with racemic starting material and chiral phosphite catalyst was also established following our understanding of the stereoretentive process. This method provides efficient access to tertiary and quaternary stereogenic centers in pyridine systems, which are prevalent in drugs, bioactive natural products, chiral ligands, and catalysts.

| S-EPMC8261767 | biostudies-literature

Asymmetric Synthesis of 2,3-Dihydrobenzofurans by a [4+1] Annulation Between Ammonium Ylides and In Situ Generated o-Quinone Methides.

Project description:A highly enantio- and diastereoselective [4+1] annulation between in situ generated ammonium ylides and o-quinone methides for the synthesis of a variety of 2,3-dihydrobenzofurans has been developed. The key factors controlling the reactivity and stereoselectivity were systematically investigated by experimental and computational means and the energy profiles obtained provide a deeper insight into the mechanistic details of this reaction.

| S-EPMC5419452 | 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