Browse
Submit Data
Databases
API
Help

Dataset Information

23 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Catalytic asymmetric synthesis of 8-oxabicyclooctanes by intermolecular [5+2] pyrylium cycloadditions.

ABSTRACT: Highly enantioselective intermolecular [5+2] cycloadditions of pyrylium ion intermediates with electron-rich alkenes are promoted by a dual catalyst system composed of an achiral thiourea and a chiral primary aminothiourea. The observed enantioselectivity is highly dependent on the substitution pattern of the 5? component, and the basis for this effect is analyzed using experimental and computational evidence. The resultant 8-oxabicyclo[3.2.1]octane derivatives possess a scaffold common in natural products and medicinally active compounds and are also versatile chiral building blocks for further manipulations. Several stereoselective complexity-generating transformations of the 8-oxabicyclooctane products are presented.

SUBMITTER: Witten MR

PROVIDER: S-EPMC4109157 | biostudies-literature | 2014 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Catalytic asymmetric synthesis of 8-oxabicyclooctanes by intermolecular [5+2] pyrylium cycloadditions.

Witten Michael R MR Jacobsen Eric N EN

Angewandte Chemie (International ed. in English) 20140429 23

Highly enantioselective intermolecular [5+2] cycloadditions of pyrylium ion intermediates with electron-rich alkenes are promoted by a dual catalyst system composed of an achiral thiourea and a chiral primary aminothiourea. The observed enantioselectivity is highly dependent on the substitution pattern of the 5π component, and the basis for this effect is analyzed using experimental and computational evidence. The resultant 8-oxabicyclo[3.2.1]octane derivatives possess a scaffold common in natur ...[more]

PMID: 24782332

Similar Datasets

The Catalytic Asymmetric Intermolecular Prins Reaction.

Project description:Despite their significant potential, catalytic asymmetric reactions of olefins with formaldehyde are rare and metal-free approaches have not been previously disclosed. Here we describe an enantioselective intermolecular Prins reaction of styrenes and paraformaldehyde to form 1,3-dioxanes, using confined imino-imidodiphosphate (iIDP) Brønsted acid catalysts. Isotope labeling experiments and computations suggest a concerted, highly asynchronous addition of an acid-activated formaldehyde oligomer to the olefin. The enantioenriched 1,3-dioxanes can be transformed into the corresponding optically active 1,3-diols, which are valuable synthetic building blocks.

| S-EPMC8679094 | biostudies-literature

Catalytic asymmetric intermolecular Stetter reaction of glyoxamides with alkylidenemalonates.

Project description:An asymmetric intermolecular Stetter reaction of glyoxamide and alkylidenemalonates has been developed. Catalyzed by a novel N-heterocyclic carbene, the Stetter adducts are formed in good yield and excellent enantioselectivity. The presence of a sensitive epimerizable stereocenter is tolerated under these mildly basic reaction conditions if a bulky amine base is used. The products may be further elaborated to provide synthetically useful intermediates.

| S-EPMC2684863 | biostudies-literature

Catalytic Asymmetric Synthesis of meta Benzene Isosteres

Project description:Aromatic rings are common elements in pharmaceutically active compounds; however, their ready oxidation can present a liability with respect to a drug's metabolic stability. Replacing these aromatic rings in pharmaceutical compounds with non-aromatic isosteric motifs can enhance properties such as potency, metabolic stability, solubility, and lipophilicity. Since the binding pockets of most pharmaceutical targets are chiral, the stereochemical configuration of the isosteric replacements are expected to have an impact on the affinity of derived ligands for target receptors. A significant impediment to this approach is the lack of simple, and scalable catalytic enantioselective syntheses of candidate isosteres from readily available precursors. In this work, we present a heretofore unknown palladium-catalyzed reaction that converts hydrocarbon-derived precursors to chiral boron-containing nortricyclanes and we show that that shape of these nortricyclanes makes them plausible isosteres for meta disubstituted aromatic rings. With chiral catalysts, the Pd-catalyzed reaction can be accomplished in an enantioselective fashion and subsequent transformation of the boron group provides access to a broad array of structures. We also show that incorporation of nortricyclanes into pharmaceutical motifs can result in improved biophysical properties along with stereochemistry-dependent activity. We anticipate that these features, coupled with the simple, inexpensive synthesis of the functionalized nortricyclane scaffold will render this platform a useful foundation for assembly of new biologically active agents.

2024-09-11 | PXD051400 | Pride

Catalytic enantioselective intermolecular cycloadditions of 2-diazo-3,6-diketoester-derived carbonyl ylides with alkene dipolarophiles.

Project description:Catalyzed cascade reactions that generate molecular complexity rapidly and in an enantioselective manner are attractive methods for asymmetric synthesis. In the present article, chiral rhodium catalysts are shown to effect such a transformation by using a range of 2-diazo-3,6-diketoesters with bicyclo[2.2.1]alkenes and styrenes as reaction partners. The reactions are likely to proceed by formation of a catalyst-complexed carbonyl ylide from the diazo compound, followed by intermolecular cycloaddition with the alkene dipolarophile. It was possible to obtain high levels of asymmetric induction [up to 89% enantiomeric excess (ee) and 92% ee for the two chiral catalysts investigated]. Enantioselectivity is not highly sensitive to substituent variation at the ketone that forms the ylide; however, branching does improve ee. Observations of dipolarophile-dependent enantiofacial selectivity in the cycloadditions indicate that the dipolarophile can be intimately involved in the enantiodiscrimination process.

| S-EPMC397403 | biostudies-literature

Cycloadditions of Oxacyclic Allenes and a Catalytic Asymmetric Entryway to Enantioenriched Cyclic Allenes.

Project description:The chemistry of strained cyclic alkynes has undergone a renaissance over the past two decades. However, a related species, strained cyclic allenes, especially heterocyclic derivatives, have only recently resurfaced and represent another class of valuable intermediates. We report a mild and facile means to generate the parent 3,4-oxacyclic allene from a readily accessible silyl triflate precursor, and then trap it in (4+2), (3+2), and (2+2) reactions to provide a variety of cycloadducts. In addition, we describe a catalytic, decarboxylative asymmetric allylic alkylation performed on an α-silylated substrate, to ultimately permit access to an enantioenriched allene. Generation and trapping of the enantioenriched cyclic allene occurs with complete transfer of stereochemical information in a Diels-Alder cycloaddition through a point-chirality, axial-chirality, point-chirality transfer process.

| S-EPMC6456397 | biostudies-literature

Catalytic Enantioselective Intermolecular [5 + 2] Dipolar Cycloadditions of a 3-Hydroxy-4-pyrone-Derived Oxidopyrylium Ylide.

Project description:The first catalytic enantioselective [5 + 2] dipolar cycloaddition of a 3-hydroxy-4-pyrone-derived oxidopyrylium ylide is described. These studies leveraged the recently recognized ability of oxidopyrylium dimers to serve as the source of ylide, which was found to be key to increasing yields and achieving enantiomeric excesses up to 99%. General reaction conditions were identified for an array of ?,?-unsaturated aldehyde dipolarophiles. Reaction products possess four stereocenters, and subsequent reduction introduced a fifth contiguous stereocenter with total stereocontrol.

| S-EPMC5831127 | biostudies-literature

Catalytic asymmetric intermolecular Stetter reaction of enals with nitroalkenes: enhancement of catalytic efficiency through bifunctional additives.

Project description:An asymmetric intermolecular Stetter reaction of enals with nitroalkenes catalyzed by chiral N-heterocyclic carbenes has been developed. The reaction rate and efficiency are profoundly impacted by the presence of catechol. The reaction proceeds with high selectivities and affords good yields of the Stetter product. Internal redox products were not observed despite of the protic conditions. The impact of catechol has been found to be general, facilitating far lower catalyst loadings than were previously achievable.

| S-EPMC3147302 | biostudies-literature

Catalytic asymmetric synthesis of geminal-dicarboxylates.

Project description:Stereogenic acetals, spiroacetals and ketals are well-studied stereochemical features that bear two heteroatoms at a common carbon atom. These stereocenters are normally found in cyclic structures while linear (or acyclic) analogues bearing two heteroatoms are rare. Chiral geminal-dicarboxylates are illustrative, there is no current way to access this class of compounds while controlling the stereochemistry at the carbon center bound to two oxygen atoms. Here we report a rhodium-catalysed asymmetric carboxylation of ester-containing allylic bromides to form stereogenic carbon centers bearing two different carboxylates with high yields and enantioselectivities. The products, which are surprisingly stable to a variety of acidic and basic conditions, can be manipulated with no loss of enantiomeric purity as demonstrated by ring closing metathesis reactions to form chiral lactones, which have been extensively used as building blocks in asymmetric synthesis.

| S-EPMC6063137 | biostudies-literature

Catalytic asymmetric formal synthesis of beraprost.

Project description:The first catalytic asymmetric synthesis of the key intermediate for beraprost has been achieved through an enantioselective intramolecular oxa-Michael reaction of an ?,?-unsaturated amide mediated by a newly developed benzothiadiazine catalyst. The Weinreb amide moiety and bromo substituent of the Michael adduct were utilized for the C-C bond formations to construct the scaffold. All four contiguous stereocenters of the tricyclic core were controlled via Rh-catalyzed stereoselective C-H insertion and the subsequent reduction from the convex face.

| S-EPMC4685892 | biostudies-literature

Catalytic asymmetric dearomatization of phenols via divergent intermolecular (3 + 2) and alkylation reactions.

Project description:The catalytic asymmetric dearomatization (CADA) reaction has proved to be a powerful protocol for rapid assembly of valuable three-dimensional cyclic compounds from readily available planar aromatics. In contrast to the well-studied indoles and naphthols, phenols have been considered challenging substrates for intermolecular CADA reactions due to the combination of strong aromaticity and potential regioselectivity issue over the multiple nucleophilic sites (O, C2 as well as C4). Reported herein are the chiral phosphoric acid-catalyzed divergent intermolecular CADA reactions of common phenols with azoalkenes, which deliver the tetrahydroindolone and cyclohexadienone products bearing an all-carbon quaternary stereogenic center in good yields with excellent ee values. Notably, simply adjusting the reaction temperature leads to the chemo-divergent intermolecular (3 + 2) and alkylation dearomatization reactions. Moreover, the stereo-divergent synthesis of four possible stereoisomers in a kind has been achieved via changing the sequence of catalyst enantiomers.

| S-EPMC10457327 | 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