Browse
Submit Data
Databases
API
Help

Dataset Information

33 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Stereocontrolled synthesis of spirooxindoles through Lewis acid-promoted [5 + 2]-annulation of chiral silyl alcohols.

ABSTRACT: The enantioselective synthesis of stereochemically and structurally diverse spirocyclic oxindoles by [5 + 2]-annulation of chiral crotylsilanes bearing a primary alcohol is described. The annulation products were further elaborated to polycyclic oxindoles by Pd(0) catalysis.

SUBMITTER: Zhang Y

PROVIDER: S-EPMC2761606 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Stereocontrolled synthesis of spirooxindoles through Lewis acid-promoted [5 + 2]-annulation of chiral silyl alcohols.

Zhang Yun Y Panek James S JS

Organic letters 20090801 15

The enantioselective synthesis of stereochemically and structurally diverse spirocyclic oxindoles by [5 + 2]-annulation of chiral crotylsilanes bearing a primary alcohol is described. The annulation products were further elaborated to polycyclic oxindoles by Pd(0) catalysis. ...[more]

PMID: 19719185

Similar Datasets

Enantioselective silyl protection of alcohols promoted by a combination of chiral and achiral Lewis basic catalysts.

Project description:Catalytic enantioselective monosilylations of diols and polyols furnish valuable alcohol-containing molecules in high enantiomeric purity. These transformations, however, require high catalyst loadings (20-30 mol%) and long reaction times (2-5 days). Here, we report that a counterintuitive strategy involving the use of an achiral co-catalyst structurally similar to the chiral catalyst provides an effective solution to this problem. A combination of seemingly competitive Lewis basic molecules can function in concert such that one serves as an achiral nucleophilic promoter and the other performs as a chiral Brønsted base. On the addition of 7.5-20 mol% of a commercially available N-heterocycle (5-ethylthiotetrazole), reactions typically proceed within one hour, and deliver the desired products in high yields and enantiomeric ratios. In some instances, there is no reaction in the absence of the achiral base, yet the presence of the achiral co-catalyst gives rise to facile formation of products in high enantiomeric purity.

| S-EPMC4001701 | biostudies-literature

Synthesis of <i>cis</i>-Oriented Vicinal Diphenylethylenes through a Lewis Acid-Promoted Annulation of Oxotriphenylhexanoates.

Project description:This study explores the synthesis of cyclic cis-vicinal phenyl ethylenes from oxotriphenylhexanoates. The reaction is a BBr3-promoted cyclization of 1,6-ketoesters (1) to five-membered diketo compounds (2). The synthesis is interesting as it constitutes one of the few examples of modular stereoselective synthesis of structures with a cis-oriented vicinal diphenylethylene. The core structure of 2 can be smoothly derivatized, which makes it a promising synthetic building block for further stereoselective synthetic applications.

| S-EPMC8279482 | biostudies-literature

Stereocontrolled cyanohydrin ether synthesis through chiral Bronsted acid-mediated vinyl ether hydrocyanation.

Project description:Vinyl ethers can be protonated to generate oxocarbenium ions that react with Me3SiCN to form cyanohydrin alkyl ethers. Reactions that form racemic products proceed efficiently upon conversion of the vinyl ether to an ?-chloro ether prior to cyanide addition in a pathway that proceeds through Brønsted acid-mediated chloride ionization. Enantiomerically enriched products can be accessed by directly protonating the vinyl ether with a chiral Brønsted acid to form a chiral ion pair. Me3SiCN acts as the nucleophile and PhOH serves as a stoichiometric proton source in a rare example of asymmetric bimolecular nucleophilic addition into an oxocarbenium ion. Computational studies have provided a model for the interaction between the catalyst and the oxocarbenium ion.

| S-EPMC3856640 | biostudies-literature

Stereoselective Synthesis of Substituted Oxocene Cores by Lewis Acid Promoted Cyclization.

Project description:Substituted oxocene derivatives have been synthesized by Lewis acid catalyzed reactions of ?-hydroxyalkene and substituted aromatic aldehydes. The Cu(OTf)2-bis-phosphine catalyzed reaction typically provides substituted dihydropyran derivatives through an olefin migration followed by a Prins cyclization. The corresponding reaction catalyzed by TMSOTf or BF3·OEt2 provided eight-membered cyclic ethers (oxocenes), selectively. This methodology provides convenient access to a variety of 2,4,8-trisubstituted oxocenes in good yields and excellent diastereoselectivities.

| S-EPMC5317094 | 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

A Lewis Acid Catalyzed annulation to 2,1-benzisoxazoles.

Project description:We report here a new, atom economical annulation to 2,1-benzisoxazole scaffolds via the BF3·Et2O-catalyzed reaction of glyoxylate esters and nitrosoarenes. The developed method represents a convergent route to this compound class from previously unexplored inputs and provides a range of 2,1-benzisoxazoles in moderate to high yields under convenient conditions. Along with exploration of substrate scope, initial mechanistic investigation through (18)O labeling and the synthesis of a reaction intermediate provides evidence for an unusual umpolung addition of glyoxylates to nitrosobenzenes with high O-selectivity, followed by a new type of Friedel-Crafts cyclization.

| S-EPMC4156248 | biostudies-literature

Asymmetric Synthesis of Spirooxindoles via Nucleophilic Epoxidation Promoted by Bifunctional Organocatalysts.

Project description:Taking into account the postulated reaction mechanism for the organocatalytic epoxidation of electron-poor olefins developed by our laboratory, we have investigated the key factors able to positively influence the H-bond network installed inside the substrate/catalyst/oxidizing agent. With this aim, we have: (i) tested a few catalysts displaying various effects that noticeably differ in terms of steric hindrance and electron demand; (ii) employed ?-alkylidene oxindoles decorated with different substituents on the aromatic ring (11a-g), the exocylic double bond (11h-l), and the amide moiety (11m-v). The observed results suggest that the modification of the electron-withdrawing group (EWG) weakly conditions the overall outcomes, and conversely a strong influence is unambiguously ascribable to either the N-protected or N-unprotected lactam framework. Specifically, when the NH free substrates (11m-u) are employed, an inversion of the stereochemical control is observed, while the introduction of a Boc protecting group affords the desired product 12v in excellent enantioselectivity (97:3 er).

| S-EPMC6017607 | biostudies-literature

A Lewis acid-promoted Pinner reaction.

Project description:Carbonitriles and alcohols react in a Lewis acid-promoted Pinner reaction to carboxylic esters. Best results are obtained with two equivalents of trimethylsilyl triflate as Lewis acid. Good yields are achieved with primary alcohols and aliphatic or benzylic carbonitriles, but the straightforward synthesis of acrylates and benzoates starting with acrylonitrile and benzonitrile, respectively, is similarly possible. Phenols are not acylated under these reaction conditions. The method has been used for the first total synthesis of the natural product monaspilosin. In the reaction of benzyl alcohols variable amounts of amides are formed in a Ritter-type side reaction.

| S-EPMC3740506 | biostudies-literature

Lewis Acid Promoted Dearomatization of Naphthols.

Project description:Two-step dearomative functionalization of naphthols promoted by Lewis acids and copper(I) catalysis was developed. Initially, Lewis acid complexation inverted the electronic properties of the ring and established an equilibrium with the dearomatized counterpart. Subsequent trapping of the dearomatized intermediate with organometallics as well as organophosphines was demonstrated and provided the corresponding dearomatized products.

| S-EPMC7894535 | biostudies-literature

Synthesis of six-membered spirooxindoles <i>via</i> a chiral Bronsted acid-catalyzed asymmetric intramolecular Friedel-Crafts reaction.

Project description:By means of the direct condensation of N-aminoethylpyrroles and isatins, followed by a chiral phosphoric acid-catalyzed asymmetric intramolecular Friedel-Crafts reaction, a new class of valuable chiral 3',4'-dihydro-2'H-spiro[indoline-3,1'-pyrrolo[1,2-a]pyrazin]-2-ones bearing a quaternary carbon stereocenter were successfully synthesized in good to excellent yields and with moderate to good enantioselectivities under mild reaction conditions.

| S-EPMC9089239 | 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