Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Intramolecular ene reaction of a chiral bicyclic lactam.

ABSTRACT: The preparation of bicylic lactam 2 is described, employing an acetoacetate-based synthesis of 1,4-ketoacid 3. The lactam 2 was shown to undergo a thermal ene reaction at 280-300 degrees C to afford tricycle 7. Reduction of the ene product followed by removal of the chiral auxiliary fragment provided the unusual lactam system 9 in highly enantioenriched form.

SUBMITTER: Resek JE

PROVIDER: S-EPMC2736314 | biostudies-literature | 2008 Dec

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Intramolecular ene reaction of a chiral bicyclic lactam.

Resek James E JE

The Journal of organic chemistry 20081201 24

The preparation of bicylic lactam 2 is described, employing an acetoacetate-based synthesis of 1,4-ketoacid 3. The lactam 2 was shown to undergo a thermal ene reaction at 280-300 degrees C to afford tricycle 7. Reduction of the ene product followed by removal of the chiral auxiliary fragment provided the unusual lactam system 9 in highly enantioenriched form. ...[more]

PMID: 18975907

Similar Datasets

Diastereoselectivity on Intramolecular Alder-ene Reaction of 1,6-Dienes.

Project description:A detailed computational study of the intramolecular Alder-ene reaction of different 1,6-dienes at M06-2X(PCM)/TZ2P level of theory has been performed. We want to understand the influence of enophile-geminal substitution pattern in the cis : trans selectivity of the cyclization process. Our analysis of the reaction coordinate by means of activation strain model of chemical reactivity (ASM-distortion interaction model) reveals that the cis-selectivity observed for unactivated reagents is related with high stabilizing orbital interaction and lower strain energy, consequence of an early transition structure. On the other hand, the presence of activating groups increases the asynchronicity of the transition structures and reduces the activation barrier due to more stabilizing orbital and electrostatic interactions, favoring trans-selectivity.

| S-EPMC10087545 | biostudies-literature

Stereoselective RNA Reaction with Chiral 2'-OH Acylating Agents

Project description:The reactivity of RNA 2'-OH groups with acylating agents has recently been investigated for high-yield conjugation of RNA strands. To date, only achiral molecules have been studied for this reaction, despite the complex chiral structure of RNA. Here we prepare a set of chiral acylimidazoles and study their stereoselectivity in RNA reactions. Reactions performed with unfolded and folded RNAs reveal that positional selectivity and reactivity vary widely with local RNA macro-chirality. We further document remarkable effects of chirality on reagent reactivity, identifying an asymmetric reagent with 1000-fold greater reactivity than prior achiral reagents. In addition, we identify a chiral compound with higher RNA structural selectivity than any previously reported RNA-mapping species. Further, azide-containing homologs of a chiral dimethylalanine reagent were synthesized and applied to local RNA labeling, displaying 92% yield and 16:1 diastereoselectivity. The results establish that reagent stereochemistry and chiral RNA structure are critical elements of small molecule-RNA reactions, and demonstrate new chemical strategies for selective RNA modification and probing.

2023-11-14 | GSE247565 | GEO

Bronsted-Acid-Catalyzed Intramolecular Carbonyl-Olefin Reactions: Interrupted Metathesis vs Carbonyl-Ene Reaction.

Project description:Lewis acid catalysts have been shown to promote carbonyl-olefin metathesis through a critical four-membered-ring oxetane intermediate. Recently, Brønsted-acid catalysis of related substrates was similarly proposed to result in a transient oxetane, which fragments within a single elementary step via a postulated oxygen-atom transfer mechanism. Herein, careful quantum chemical investigations show that Brønsted acid (triflic acid, TfOH) instead invokes a mechanistic switch to a carbonyl-ene reaction, and oxygen-atom transfer is uncompetitive. TfOH's conjugate base is also found to rearrange H atoms and allow isomerization of the carbocations that appear after the carbonyl-ene reaction. The mechanism explains available experimental information, including the skipped diene species that appear transiently before product formation. The present study clarifies the mechanism for activation of intramolecular carbonyl-olefin substrates by Brønsted acids and provides important insights that will help develop this exciting class of catalysts.

| S-EPMC8117943 | biostudies-literature

Scope of the asymmetric intramolecular stetter reaction catalyzed by chiral nucleophilic triazolinylidene carbenes.

Project description:A highly enantioselective intramolecular Stetter reaction of aromatic and aliphatic aldehydes tethered to different Michael acceptors has been developed. Two triazolium scaffolds have been identified that catalyze the intramolecular Stetter reaction with good reactivity and enantioselectivity. The substrate scope has been examined and found to be broad; both electron-rich and -poor aromatic aldehydes undergo cyclization in high yield and enantioselectivity. The tether can include oxygen, sulfur, nitrogen, and carbon linkers with no detrimental effects. In addition, the incorporation of various tethered Michael acceptors includes amides, esters, thioesters, ketones, aldehydes, and nitriles. The catalyst loading may be reduced to 3 mol % without significantly affecting the reactivity or selectivity of the reaction.

| S-EPMC4222522 | biostudies-literature

An approach to new chiral bicyclic imines and amines <i>via</i> Horner-Wadsworth-Emmons reaction.

Project description:New chiral bicyclic imines, enamines and amines were prepared via Horner-Wadsworth-Emmons reaction of hexahydroquinoxalin-2(1H)-one-derived phosphonate, as the source of a phosphonate carbanion, and a wide range of structurally diverse carbonyl substrates. The simplicity of the synthetic protocol, high selectivity, and broad substrate scope are the main advantages of the presented methodology.

| S-EPMC9052066 | biostudies-literature

Type 2 intramolecular N-acylazo Diels-Alder reaction: regio- and stereoselective synthesis of bridgehead bicyclic 1,2-diazines.

Project description:The type 2 intramolecular N-acylazo Diels-Alder reaction provides a regio- and stereoselective synthesis of bicyclic 1,2-diazine systems. A new method for the generation of N-acylazo dienophiles with tetra-n-butylammonium periodate is reported. X-ray crystallographic analysis allowed the quantification of structural distortions of the nonplanar bridgehead olefin and lactam functionalities in 1,2-diazine cycloadducts 11 and 15. Caprolactams and enantholactams were formed by stereoselective bridgehead alkene reduction, a process that transfers stereochemistry from the bridgehead lactam nitrogen to the bridgehead carbon. The sequence of transformations offers a convenient route for the diastereoselective synthesis of medium-ring nitrogen heterocycles and 1,4-diamines.

| S-EPMC3192005 | biostudies-literature

Tandem cross enyne metathesis (CEYM)-intramolecular Diels-Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds.

Project description:A new tandem cross enyne metathesis (CEYM)-intramolecular Diels-Alder reaction (IMDAR) has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of linear bicyclic scaffolds in a very simple manner with moderate to good levels of diastereoselectivity. This methodology constitutes one of the few examples that employ olefins differently than ethylene in tandem CEYM-IMDAR protocols.

| S-EPMC4578421 | biostudies-literature

Inherently chiral nor-heteracalixarenes: design and synthesis <i>via</i> enantioselective intramolecular Suzuki-Miyaura reaction.

Project description:There has been a recent upsurge in research aimed at synthesizing inherently chiral molecules devoid of point, axial, planar and helical chiralities. We present herein our design and enantioselective synthesis of a series of inherently chiral macrocycles. These compounds, termed nor-heteracalixaromatics, feature a biaryl bond that replaces one of the aryl-heteroatom-aryl linkages found in classic heteracalix[4]aromatics. Macrocyclization of linear achiral substrates via an intramolecular Suzuki-Miyaura cross-coupling reaction affords the 15-membered cyclophane without any chiral elements in high yields and enantioselectivities. Notably, the formation of the aryl-aryl bond does not induce axial chirality at the biaryl linkage. Instead, it restricts the free rotation of an aromatic ring located four bonds away, leading to the inherent chirality of the macrocycle. The intriguing chiroptical properties of these compounds made them promising platform for the development of CPL emitters.

| S-EPMC11304768 | biostudies-literature

Enantioselective synthesis of 5,7-bicyclic ring systems from axially chiral allenes using a Rh(I)-catalyzed cyclocarbonylation reaction.

Project description:A transfer of chirality in an intramolecular Rh(I)-catalyzed allenic Pauson-Khand reaction (APKR) to access tetrahydroazulenones, tetrahydrocyclopenta[c]azepinones and dihydrocyclopenta[c]oxepinones enantioselectively (22-99% ee) is described. The substitution pattern of the allene affected the transfer of chiral information. Complete transfer of chirality was obtained for all trisubstituted allenes, but loss of chiral information was observed for disubstituted allenes. This work constitutes the first demonstration of a transfer of chiral information from an allene to the 5-position of a cyclopentenone using a cyclocarbonylation reaction. The absolute configuration of the corresponding cyclocarbonylation product was also established, something that is rarely done.

| S-EPMC3634128 | biostudies-literature

Organocatalyzed Intramolecular Carbonyl-Ene Reactions.

Project description:An organocatalyzed intramolecular carbonyl-ene reaction was developed to produce carbocyclic and heterocyclic 5- and 6-membered rings from a citronellal-derived trifluoroketone and a variety of aldehydes. A phosphoramide derivative was found to promote the cyclization of the trifluoroketone, whereas a less acidic phosphoric acid proved to be a superior catalyst for the aldehyde substrates.

| S-EPMC6272844 | biostudies-other

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