Browse
Submit Data
Databases
API
Help

Dataset Information

15 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Arylsulfonate-based nucleophile assisting leaving groups.

ABSTRACT: [Chemical reaction: See text] The synthesis and unique reactivity of a series of arylsulfonate-based nucleophile assisting leaving groups (NALG) containing oligomeric ether units (including crown ethers) attached to the arylsulfonyl ring in the ortho orientation are described. The reactions of a variety of these ether-containing alkyl sulfonates with metal halides proceeded at substantially greater rates than electronically similar sulfonates. These ether-containing leaving groups also displayed marked selectivity for lithium halides relative to the corresponding sodium and potassium salts in nucleophilic displacement reactions.

SUBMITTER: Lepore SD

PROVIDER: S-EPMC3563673 | biostudies-literature | 2005 Sep

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Arylsulfonate-based nucleophile assisting leaving groups.

Lepore Salvatore D SD Bhunia Anjan K AK Cohn Pamela P

The Journal of organic chemistry 20050901 20

[Chemical reaction: See text] The synthesis and unique reactivity of a series of arylsulfonate-based nucleophile assisting leaving groups (NALG) containing oligomeric ether units (including crown ethers) attached to the arylsulfonyl ring in the ortho orientation are described. The reactions of a variety of these ether-containing alkyl sulfonates with metal halides proceeded at substantially greater rates than electronically similar sulfonates. These ether-containing leaving groups also displayed ...[more]

PMID: 16277337

Similar Datasets

Nucleophile assisting leaving groups: a strategy for aliphatic 18F-fluorination.

Project description:A series of arylsulfonate nucleophile assisting leaving groups (NALGs) were prepared in which the metal chelating unit is attached to the aryl ring via an ether linker. These NALGs exhibited significant rate enhancements in halogenation reactions using metal halides. Studies with a NALG containing a macrocyclic ether unit suggest that rate enhancements of these nucleophilic halogenation reactions are facilitated by stabilization of charge in the transition state rather than through strong precomplexation with metal cation. In several cases, a primary substrate containing one of the new leaving groups rivaled or surpassed the reactivity of triflates when exposed to nucleophile but was otherwise highly stable and isolable. These and previously disclosed chelating leaving groups were used in (18)F-fluorination reactions using no-carrier-added [18F]fluoride ion (t(1/2) = 109.7 min, beta+ = 97%) in CH3CN. Under microwave irradiation and without the assistance of a cryptand, such as K2.2.2, primary substrates with select NALGs led to a substantial improvement (2-3-fold) in radiofluorination yields over traditional leaving groups.

| S-EPMC2765794 | biostudies-literature

Enhanced Nucleophilic Fluorination and Radiofluorination of Organosilanes Appended with Potassium-Chelating Leaving Groups.

Project description:Here we aimed to explore the feasibility of enhancing the fluorination of organosilanes by appending potassium-chelating groups to the substrates. For this purpose, eight organosilanes were prepared in which a linear or cyclic leaving group, with putative potassium-chelating ability, was attached covalently to a congested silicon atom via an ether linkage to serve as a potential nucleophilic assisting leaving group (NALG). Organosilicon-NALGs with expected strong potassium-chelating capability enhanced reactions with potassium fluoride in acetonitrile to produce organofluorosilanes without any need to separately add phase transfer reagent. Similar rate enhancements were also observed with cyclotron-produced [18F]fluoride ion (t1/2 = 109.7 min, ?+ = 97%) in the presence of potassium carbonate in MeCN-0.5% H2O. This study found that metal-chelating NALG units can accelerate fluorination and radiofluorination reactions at sterically crowded silicon atoms.

| S-EPMC3956301 | biostudies-literature

Multiple roles of aryloxide leaving groups in enantioselective annulations employing ?,?-unsaturated acyl ammonium catalysis.

Project description:An isothiourea-catalysed Michael addition-annulation process using ?-fluoroalkyl-substituted ?,?-unsaturated aryl esters and a range of 2-acylbenzazoles is reported for the enantioselective synthesis of dihydropyranone and dihydropyridinone products bearing polyfluorinated stereocenters (29 examples, up to 98% yield, >99?:?1 er). The choice of aryl group of the aryl ester proved essential in determining reaction enantioselectivity and dihydropyranone?:?dihydropyridinone product selectivity. The aryloxide leaving group is shown to play a number of essential additional roles, operating (i) as a Brønsted base, circumventing the need for an auxiliary base; and (ii) as a Lewis base to catalyse the isomerisation of dihydropyranone products into thermodynamically-favoured dihydropyridinones. After optimisation, this isomerisation process was exploited for the selective synthesis of dihydropyridinone products using acylbenzothiazoles, and either dihydropyranone or dihydropyridinone products using acylbenzoxazoles. Finally, the phenol derivative, produced following protonation of the aryloxide, is proposed to act as a Brønsted acid, which promotes an isothiourea-catalysed kinetic resolution of benzoxazole-derived dihydropyranones.

| S-EPMC5982221 | biostudies-literature

The arrangement of substrate and organophosphorus-inhibitor leaving groups in acetylcholinesterase active site.

Project description:The leaving groups of serine esterase substrates and organophosphorus inhibitors bind to different loci at the enzyme active site. Kinetic proof of this general conclusion is presented in the case of acetylcholinesterase reactions. The proposed model for acetylcholinesterase active site provides a new stereochemical mechanism for the phosphorylated enzyme reactivation.

| S-EPMC1183730 | biostudies-other

Sulfonium salts as leaving groups for aromatic labelling of drug-like small molecules with fluorine-18.

Project description:Positron emission tomography (PET) is unique in that it allows quantification of biochemical processes in vivo, but difficulties with preparing suitably labelled radiotracers limit its scientific and diagnostic applications. Aromatic [(18)F]fluorination of drug-like small molecules is particularly challenging as their functional group compositions often impair the labelling efficiency. Herein, we report a new strategy for incorporation of (18)F into highly functionalized aromatic compounds using sulfonium salts as leaving groups. The method is compatible with pharmacologically relevant functional groups, including aliphatic amines and basic heterocycles. Activated substrates react with [(18)F]fluoride at room temperature, and with heating the reaction proceeds in the presence of hydrogen bond donors. Furthermore, the use of electron rich spectator ligands allows efficient and regioselective [(18)F]fluorination of non-activated aromatic moieties. The method provides a broadly applicable route for (18)F labelling of biologically active small molecules, and offers immediate practical benefits for drug discovery and imaging with PET.

| S-EPMC4404714 | biostudies-literature

The effect of leaving groups on binding and reactivity in enzyme-free copying of DNA and RNA.

Project description:The template-directed incorporation of nucleotides at the terminus of a growing primer is the basis of the transmission of genetic information. Nature uses polymerases-catalyzed reactions, but enzyme-free versions exist that employ nucleotides with organic leaving groups. The leaving group affects yields, but it was not clear whether inefficient extensions are due to poor binding, low reactivity toward the primer, or rapid hydrolysis. We have measured the binding of a total of 15 different activated nucleotides to DNA or RNA sequences. Further, we determined rate constants for the chemical step of primer extension involving methylimidazolides or oxyazabenzotriazolides of deoxynucleotides or ribonucleotides. Binding constants range from 10 to >500 mM and rate constants from 0.1 to 370 M(-1) h(-1) For aminoterminal primers, a fast covalent step and slow hydrolysis are the main factors leading to high yields. For monomers with weakly pairing bases, the leaving group can improve binding significantly. A detailed mechanistic picture emerges that explains why some enzyme-free primer extensions occur in high yield, while others remain recalcitrant to copying without enzymatic catalysis. A combination of tight binding and rapid extension, coupled with slow hydrolysis induces efficient enzyme-free copying.

| S-EPMC4937335 | biostudies-literature

Ring-Closing Synthesis of Dibenzothiophene Sulfonium Salts and Their Use as Leaving Groups for Aromatic 18F-Fluorination.

Project description:Herein, we report a novel intramolecular ring-closing reaction of biaryl thioethers that give access to highly functionalized dibenzothiophene sulfonium salts under mild conditions. The resulting precursors react regioselectively with [18F]fluoride to give [18F]fluoroarenes in predictable radiochemical yields. The strategy expands the available radiochemical space and provides superior labeling efficiency for clinically relevant PET tracers.

| S-EPMC6128620 | biostudies-literature

A Modular Synthesis of Teraryl-Based α-Helix Mimetics, Part 4: Core Fragments with Two Halide Leaving Groups Featuring Side Chains of Proteinogenic Amino Acids.

Project description:Teraryl-based α-helix mimetics have proven to be useful compounds for the inhibition of protein-protein interactions (PPI). We have developed a modular and flexible approach for the synthesis of teraryl-based α-helix mimetics using a benzene core unit featuring two halide leaving groups of differentiated reactivity in the Pd-catalyzed cross-coupling used for teraryl assembly. The use of para-bromo iodoarene core fragments resolved the issue of hydrolysis during cross-coupling that was observed when using triflate as a leaving group. We report a complete set of para-bromoiodoarene core fragments decorated with side chains of all proteinogenic amino acids relevant for PPI (Ala, Arg, Asn, Asp, Cys, Gln, Glu, His, Ile, Leu, Lys, Met, Phe, Ser, Thr, Trp, Tyr and Val). In order to be compatible with general cross-coupling conditions, some of the nucleophilic side chains had to be provided in a protected form to serve as stable building blocks.

| S-EPMC9304293 | biostudies-literature

New modification of the Perkow reaction: halocarboxylate anions as leaving groups in 3-acyloxyquinoline-2,4(1H,3H)-dione compounds.

Project description:Substituted 3-(fluoroacyloxy)quinoline-2,4(1H,3H)-diones including 3-(fluoroiodoacetoxy) derivatives react with triethyl phosphite to afford either the product of the Perkow reaction or the corresponding 4-ethoxyquinolin-2(1H)-one. In both reactions, the fluorocarboxylate anion acts as the first observed leaving group. This observation restricts the application of the intramolecular Horner-Wadsworth-Emmons synthesis to modify quinoline-2,4(1H,3H)-diones by the annulation of fluorinated but-2-enolide rings.

| S-EPMC1399465 | biostudies-literature

1,2,3-Triazoles as leaving groups in S<sub>N</sub>Ar-Arbuzov reactions: synthesis of C6-phosphonated purine derivatives.

Project description:A new method for C-N bond transformations into C-P bonds was developed using 1,2,3-triazoles as leaving groups in SNAr-Arbuzov reactions. A series of C6-phosphonated 2-triazolylpurine derivatives was synthesized for the first time, with the isolated yields reaching up to 82% in the C-P-bond-forming event. The SNAr-Arbuzov reaction of 2,6-bistriazolylpurines follows the general regioselectivity pattern of the C6-position being more reactive towards substitution, which was unambiguously proved by X-ray analysis of diethyl (9-heptyl-2-(4-phenyl-1H-1,2,3-triazol-1-yl)-9H-purin-6-yl)phosphonate.

| S-EPMC7849246 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

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