Project description:One of the most efficient and reliable approaches to construct C-C bonds involves the conjugate addition of carbon nucleophiles to electron-deficient ketones. Yet, 1,6-conjugate additions of extended conjugated systems largely remain underexplored due to difficulties in controlling the regioselectivity. Herein, we report umpolung aldehydes as carbanion equivalents for highly regioselective 1,6-conjugate addition reactions to unsaturated ketones, with preliminary studies of the enantioselective variant. The synergy of ruthenium(ii) catalyst and electron-rich, bidentate phosphine ligand is essential for the reactivity and selectivity under mild reaction conditions.

| S-EPMC8694324 | biostudies-literature

Boron-Promoted Deprotonative Conjugate Addition: Geminal Diborons as Soft Pronucleophiles and Acyl Anion Equivalents.

Project description:Conjugate addition of α-boron-stabilized carbanions is an underexplored reaction modality. Existing methods require deborylation of geminal di-/triboryl alkanes and/or the presence of additional activating groups. We report the 1,4-addition of α,α-diboryl carbanions generated via deprotonation of the corresponding geminal diborons. The methodology provided a general route to highly substituted and synthetically useful γ,γ-diboryl ketones. The development of geminal diborons as soft pronucleophiles also enabled their use as acyl anion equivalents via a one-pot tandem conjugate addition-oxidation sequence.

| S-EPMC9509689 | biostudies-literature

Catalytic enantioselective conjugate addition en route to paxilline indoloterpenoids.

Project description:Development of enantioselective synthesis of precursor en route to paxilline indoloterpenoids is described. Evaluation of 25 diphosphine-based ligands has led to identification of JosiPhos derivative that allows for asymmetric conjugate addition of homoprenyl Grignard reagent to 2-methylcyclopent-2-en-1-one in excellent yield and with appreciable levels of enantioinduction. Application to the conjugate addition of other Grignard reagents is demonstrated.

| S-EPMC7561000 | biostudies-literature

A mild catalytic system for radical conjugate addition of nitrogen heterocycles.

Project description:The direct addition of pyridine and diazine units to electron-poor alkenes has been achieved via a redox radical mechanism that is enabled by limiting the effective concentration of the hydrogen-atom source. The described method is tolerant of acidic functional groups and is generally applicable to the union of a wide range of Michael acceptors and 6-membered heterocyclic halides.

| S-EPMC5412691 | biostudies-literature

Catalytic asymmetric conjugate addition of simple alkyl thiols to alpha,beta-unsaturated N-acylated oxazolidin-2-ones with bifunctional catalysts.

Project description:In this communication, we describe an unprecedented highly enantioselective catalytic conjugate addition of simple alkyl thiols to alpha,beta-unsaturated N-acylated oxazolidin-2-ones catalyzed by acid-base bifunctional catalysis. This reaction provides a useful catalytic method for the synthesis of optically active chiral sulfur compounds that are otherwise difficult to prepare by asymmetric catalysis. The successful development of this reaction resulted from a discovery that, upon proper modification, a cinchona alkaloid bearing a thiourea functionality at 6' position can afford highly efficient catalysis for asymmetric conjugate additions.

| S-EPMC2730660 | biostudies-literature

Kinetic Resolution of β-Branched Aldehydes through Peptide-Catalyzed Conjugate Addition Reactions.

Project description:The catalytic kinetic resolution of racemic β-branched aldehydes offers a straightforward stereoselective entry to aldehydes and addition products. Yet, control over stereoselectivity is difficult due to the conformational flexibility of β-branched aldehydes. Here, we show that the peptide catalyst H-dPro-αMePro-Glu-NH2 resolves β-branched aldehydes through reaction with nitroolefins and provides γ-nitroaldehydes with three consecutive stereogenic centers in high yields and stereoselectivities. Kinetic, NMR spectroscopic, and computational studies provided insights into the selectivity-determining step and origins of the kinetic resolution.

| S-EPMC11258695 | biostudies-literature

Synthesis of α,α'-trans-oxepanes through an organocatalytic oxa-conjugate addition reaction.

Project description:Oxepanes are found in a wide range of natural products; however, they are challenging synthetic targets due to enthalpic and entropic barriers. Organocatalytic oxa-conjugate addition reactions promoted by the gem-disubstituent (Thorpe-Ingold) effect stereoselectively provided α,α'-trans-oxepanes. In addition, the potential of an organocatalytic tandem oxa-conjugate addition/α-oxidation was demonstrated in a rapid generation of molecular complexity. These organocatalytic oxa-conjugate addition reactions would provide powerful tools for the synthesis of natural products that contain highly functionalized oxepanes.

| S-EPMC4018174 | biostudies-literature

Generation of the Methoxycarbonyl Radical by Visible-Light Photoredox Catalysis and Its Conjugate Addition with Electron-Deficient Olefins.

Project description:Visible-light photoredox-catalyzed fragmentation of methyl N-phthalimidoyl oxalate allows the direct construction of a 1,4-dicarbonyl structural motif by a conjugate addition of the methoxycarbonyl radical to reactive Michael acceptors. The regioselectivity of the addition of this alkoxyacyl radical species to electron-deficient olefins is heavily influenced by the electronic nature of the acceptor, behavior similar to that exhibited by nucleophilic alkyl radicals.

| S-EPMC4892945 | biostudies-literature

Catalytic asymmetric addition of dialkylzinc reagents to alpha-aldiminoesters.

Project description:[reaction: see text] The first catalytic, enantioselective addition of organozinc reagents to alpha-aldiminoesters is described. The use of a Lewis acid/Lewis base containing bifunctional catalyst preorganizes both reactive substrates to promote enantioselective addition over the racemic background reaction and alternative addition modes. Alcohol additives were found to enhance the enantioselection. The addition product was also found to cyclize with remaining substrate to provide imidazolidines.

| S-EPMC3289996 | 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