Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Allenoate Prenucleophiles: A Triply Diastereoselective Approach to β-Hydroxy Esters Containing All-Carbon α-Quaternary Centers.

ABSTRACT: Allenyl esters activated by titanium(IV) underwent additions to a wide range of aldehydes in high regio- and diastereoselectivities leading to products containing an all-carbon quaternary center bearing an α-vinyl group that was installed with high selectivity for the Z-geometry. An aldol product was also converted to an indanone offering a new route to this important compound class. Product triple diastereoselectivity has been rationalized using a concerted transition-state model.

SUBMITTER: Maki SL

PROVIDER: S-EPMC9360042 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Allenoate Prenucleophiles: A Triply Diastereoselective Approach to β-Hydroxy Esters Containing All-Carbon α-Quaternary Centers.

Maki Samantha L SL Maity Pradip P Dougherty Shannon S Johns Jennifer J Lepore Salvatore D SD

Organic letters 20190916 19

Allenyl esters activated by titanium(IV) underwent additions to a wide range of aldehydes in high regio- and diastereoselectivities leading to products containing an all-carbon quaternary center bearing an α-vinyl group that was installed with high selectivity for the <i>Z</i>-geometry. An aldol product was also converted to an indanone offering a new route to this important compound class. Product triple diastereoselectivity has been rationalized using a concerted transition-state model. ...[more]

PMID: 31524414

Similar Datasets

Structure and Properties of Poly-α-olefins Containing Quaternary Carbon Centers.

Project description:In this paper, poly-α-olefins (PAO) containing quaternary carbon centers were prepared by two-step oligomerization using a metallocene catalyst followed by a Ziegler-Natta catalyst. First, the 1-decene dimer was oligomerized with [t-BuN(Me)2C(η5-C5H4)]ZrCl2, and the effects of the oligomerization temperature, Al/Zr molar ratio, and catalyst loading on the oligomerization were investigated. In the second step, the obtained 1-decene dimers were copolymerized with 1-decene with TiCl4/Et2AlCl, and the effects of the catalysts, monomer/dimer ratio, and α-olefin species on the copolymerization were investigated. The composition and structure of the dimers and copolymerization products were characterized by gas chromatography (GC) and 1H NMR and 13C NMR spectroscopy. The results of GC and 13C NMR analyses indicated that the metallocene catalyzed the formation of the 1-decene oligomerization product, resulting in the branched olefin dimer being the major product, and the existence of quaternary carbons in the 1-decene/1-decene dimer copolymerization product could also be found. The polymerization mechanism for the formation of the quaternary carbon centers is proposed. The 1-decene/1-decene dimer copolymerization product containing quaternary carbon centers has a kinematic viscosity of 10.8 mm2/s at 100 °C, a viscosity index of 165, and a pour point of -52 °C; thus, the product with quaternary carbon centers has a better viscosity-temperature performance and low-temperature fluidity than those of the 1-decene oligomerization product and typical PAO products, but the kinematic viscosity is similar.

| S-EPMC7191570 | biostudies-literature

Synthesis of Structurally Diverse N-Substituted Quaternary-Carbon-Containing Small Molecules from α,α-Disubstituted Propargyl Amino Esters.

Project description:N-containing quaternary stereocenters represent important motifs in medicinal chemistry. However, due to their inherently sterically hindered nature, they remain underrepresented in small molecule screening collections. As such, the development of synthetic routes to generate small molecules that incorporate this particular feature are highly desirable. Herein, we describe the diversity-oriented synthesis (DOS) of a diverse collection of structurally distinct small molecules featuring this three-dimensional (3D) motif. The subsequent derivatisation and the stereoselective synthesis exemplified the versatility of this strategy for drug discovery and library enrichment. Chemoinformatic analysis revealed the enhanced sp3 character of the target library and demonstrated that it represents an attractive collection of biologically diverse small molecules with high scaffold diversity.

| S-EPMC6220872 | biostudies-literature

An Enantio- and Diastereoselective Chemoenzymatic Synthesis of α-Fluoro β-Hydroxy Carboxylic Esters.

Project description:The trans-o-hydroxybenzylidene pyruvate aldolase-catalysed reactions between fluoropyruvate and many (hetero)aromatic aldehydes yield aldol adducts without subsequent dehydration. Treatment of the reaction products with hydrogen peroxide yields the corresponding syn-configured α-fluoro β-hydroxy carboxylic acids which have >98 % ee. The overall chemoenzymatic approach, in which fluoropyruvate serves as a fluoroacetate equivalent, may be exploited in the synthesis of polar building blocks and fragments with potential value in drug discovery.

| S-EPMC5074308 | biostudies-literature

Synthesis of Quaternary Carbon Stereogenic Centers by Diastereoselective Conjugate Addition of Boron-Stabilized Allylic Nucleophiles to Enones.

Project description:A method for the site-selective and diastereoselective conjugate addition of boron-stabilized allylic nucleophiles to α,β-unsaturated ketones is disclosed. Transformations involve easily prepared γ,γ-disubstituted allyldiboron reagents and proceed in the presence of a fluoride activator at 80 °C. Reactions proceed with a wide variety of enones and allyldiboron reagents efficiently to deliver ketone products that contain otherwise difficult-to-access vicinal β-tertiary and γ-quaternary carbon stereogenic centers and an alkenylboron moiety. The utility of the method is highlighted by several transformations, including cross-coupling and carbocyclizations.

| S-EPMC7289652 | biostudies-literature

Catalytic Enantio- and Diastereoselective Cyclopropanation of 2-Azadienes for the Synthesis of Aminocyclopropanes Bearing Quaternary Carbon Stereogenic Centers.

Project description:We report the catalytic enantio- and diastereoselective preparation of aminocyclopropanes by the cyclopropanation of terminal and (Z)-internal 2-azadienes with donor/acceptor carbenes derived from α-diazoesters. The resulting cyclopropanes bear quaternary carbon stereogenic centers vicinal to the amino-substituted carbon and are formed as a single diastereomer in up to 99:1 er and 97% yield with 0.5 mol % of Rh2(DOSP)4 and only 1.5 equiv of the diazo reagent. Transformations with internal azadienes afford cyclopropanes with three contiguous stereogenic centers.

| S-EPMC6790987 | biostudies-literature

Diversification reactions of γ-silyl allenyl esters: selective conversion to all-carbon quaternary centers and γ-allene dicarbinols.

Project description:The unique reactivity of γ-silyl allenyl esters is described. Taking advantage of the silyl group as a fluoride acceptor, these allenoates readily underwent addition to a variety of electrophiles to selectively yield products with all-carbon quaternary centers or allenoate dicarbinols. These dicarbinols were subsequently converted to novel highly substituted 6-hydro-2-pyrones.

| S-EPMC5510162 | biostudies-literature

Stereocontrolled alkylative construction of quaternary carbon centers.

Project description:Protocols for the stereodefined formation of alpha,alpha-disubstituted enolates of pseudoephedrine amides are presented followed by the implementation of these in diastereoselective alkylation reactions. Direct alkylation of alpha,alpha-disubstituted pseudoephedrine amide substrates is demonstrated to be both efficient and diastereoselective across a range of substrates, as exemplified by alkylation of the diastereomeric pseudoephedrine alpha-methylbutyramides, where both substrates are found to undergo stereospecific replacement of the alpha-C-H bond with alpha-C-alkyl, with retention of stereochemistry. This is shown to arise by sequential stereospecific enolization and alkylation reactions, with the alkyl halide attacking a common pi-face of the E- and Z-enolates, proposed to be opposite the pseudoephedrine alkoxide side chain. Pseudoephedrine alpha-phenylbutyramides are found to undergo highly stereoselective but not stereospecific alpha-alkylation reactions, which evidence suggests is due to facile enolate isomerization. Also, we show that alpha,alpha-disubstituted pseudoephedrine amide enolates can be generated in a highly stereocontrolled fashion by conjugate addition of an alkyllithium reagent to the s-cis-conformer of an alpha-alkyl-alpha,beta-unsaturated pseudoephedrine amide, providing alpha,alpha-disubstituted enolate substrates that undergo alkylation in the same sense as those formed by direct deprotonation. Methods are presented to transform the alpha-quaternary pseudoephedrine amide products into optically active carboxylic acids, ketones, primary alcohols, and aldehydes.

| S-EPMC2666470 | biostudies-literature

Synthesis of quaternary carbon centers via hydroformylation.

Project description:The application of hydroformylation to the synthesis of quaternary carbon centers is reported. The synthesis of the highly substituted carbon is achieved by applying a catalytic amount of 1. Ligand 1 serves as a catalytic directing group by covalently and reversibly binding to both the substrate and catalyst. The intramolecular nature of the directing group strategy accelerates the hydroformylation reaction such that the reaction is performed at mild temperatures (35-55 degrees C) and with excellent regioselectivity (b:l > 94:6).

| S-EPMC2928406 | biostudies-literature

Formation of All-Carbon Quaternary Centers via Enantioselective Pd-Catalyzed α-Vinylation of γ-Lactams.

Project description:Herein, we report an enantioselective vinylation of α-substituted γ-lactams that forges quaternary centers in up to 59% yield with 94% ee. The use of canonically inactive vinyl chloride electrophiles afforded the highest yields and levels of stereoselectivity, and a range of trisubstituted vinyl chlorides were found to be proficient in promoting this transformation. These stereogenic products could be further elaborated to functionally rich scaffolds, thereby highlighting the synthetic utility of this process.

| S-EPMC11406581 | biostudies-literature

Palladium-Catalyzed Alkoxycarbonylation of Alcohols for the Synthesis of Cyclobutanecarboxylates with α-Quaternary Carbon Centers.

Project description:A palladium-catalyzed alkoxycarbonylation with two different alcohols for the synthesis of cyclobutanecarboxylates bearing an α-quaternary carbon center is presented. The reaction utilizes readily accessible starting materials, tolerates a broad scope of functional groups, and provides a straightforward and efficient approach for the synthesis of a diverse array of cyclobutanecarboxylates bearing an α-quaternary carbon. Meanwhile, this strategy effectively prevents the transition-metal-catalyzed ring-opening of cyclobutanols, preserves the cyclobutane framework, and affords 1,1-disubstituted cyclobutanecarboxylates in high yields with excellent regioisomeric ratios.

| S-EPMC11811996 | 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