Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Mechanistic Pathways in Amide Activation: Flexible Synthesis of Oxazoles and Imidazoles.

ABSTRACT: The preparation of substituted aminooxazoles and aminoimidazoles from ?-arylamides and ?-aminoamides through triflic anhydride-mediated amide activation is reported. These reactions proceed via the intermediacy of nitrilium adducts and feature N-oxide-promoted umpolung of the ?-position of amides as well as a mechanistically intriguing sequence that results in sulfonyl migration from nitrogen to carbon. Quantum-chemical mechanistic analysis sheds light on the intricacies of the process.

SUBMITTER: Di Mauro G

PROVIDER: S-EPMC5525102 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Mechanistic Pathways in Amide Activation: Flexible Synthesis of Oxazoles and Imidazoles.

Di Mauro Giovanni G Maryasin Boris B Kaiser Daniel D Shaaban Saad S González Leticia L Maulide Nuno N

Organic letters 20170713 14

The preparation of substituted aminooxazoles and aminoimidazoles from α-arylamides and α-aminoamides through triflic anhydride-mediated amide activation is reported. These reactions proceed via the intermediacy of nitrilium adducts and feature N-oxide-promoted umpolung of the α-position of amides as well as a mechanistically intriguing sequence that results in sulfonyl migration from nitrogen to carbon. Quantum-chemical mechanistic analysis sheds light on the intricacies of the process. ...[more]

PMID: 28703599

Similar Datasets

Gold-catalyzed tandem reactions of amide-aldehyde-alkyne coupling and cyclization-synthesis of 2,4,5-trisubstituted oxazoles.

Project description:We report the first cationic gold(i)-catalyzed one-pot reaction of amide, alkyne and aldehyde followed by cyclization, to successfully access highly substituted oxazoles derivatives in good yields. A single catalyst allows the occurring of this multi-step reaction atom- and step-economically, with water as the only theoretical side product.

| S-EPMC5950834 | biostudies-other

Continuous multistep synthesis of 2-(azidomethyl)oxazoles.

Project description:An efficient three-step protocol was developed to produce 2-(azidomethyl)oxazoles from vinyl azides in a continuous-flow process. The general synthetic strategy involves a thermolysis of vinyl azides to generate azirines, which react with bromoacetyl bromide to provide 2-(bromomethyl)oxazoles. The latter compounds are versatile building blocks for nucleophilic displacement reactions as demonstrated by their subsequent treatment with NaN3 in aqueous medium to give azido oxazoles in good selectivity. Process integration enabled the synthesis of this useful moiety in short overall residence times (7 to 9 min) and in good overall yields.

| S-EPMC5827817 | biostudies-literature

Near-Ambient-Temperature Dehydrogenative Synthesis of the Amide Bond: Mechanistic Insight and Applications.

Project description:The current existing methods for the amide bond synthesis via acceptorless dehydrogenative coupling of amines and alcohols all require high reaction temperatures for effective catalysis, typically involving reflux in toluene, limiting their potential practical applications. Herein, we report a system for this reaction that proceeds under mild conditions (reflux in diethyl ether, boiling point 34.6 °C) using ruthenium PNNH complexes. The low-temperature activity stems from the ability of Ru-PNNH complexes to activate alcohol and hemiaminals at near-ambient temperatures through the assistance of the terminal N-H proton. Mechanistic studies reveal the presence of an unexpected aldehyde-bound ruthenium species during the reaction, which is also the catalytic resting state. We further utilize the low-temperature activity to synthesize several simple amide bond-containing commercially available pharmaceutical drugs from the corresponding amines and alcohols via the dehydrogenative coupling method.

| S-EPMC8218306 | biostudies-literature

Synthesis of Novel Heterocycles by Amide Activation and Umpolung Cyclization.

Project description:Herein, we report a metal-free synthesis of cyclic amidines, oxazines, and an oxazinone under mild conditions by electrophilic amide activation. This strategy features an unusual Umpolung cyclization mode and enables the smooth union of α-aryl amides and diverse alkylazides, effectively rerouting our previously reported α-amination transform.

| S-EPMC7091535 | biostudies-literature

Discovery of competing anaerobic and aerobic pathways in umpolung amide synthesis allows for site-selective amide 18O-labeling.

Project description:The mechanism of umpolung amide synthesis was probed by interrogating potential sources for the oxygen of the product amide carbonyl that emanates from the α-bromo nitroalkane substrate. Using a series of (18)O-labeled substrates and reagents, evidence is gathered to advance two pathways from the putative tetrahedral intermediate. Under anaerobic conditions, a nitro-nitrite isomerization delivers the amide oxygen from nitro oxygen. The same homolytic nitro-carbon fragmentation can be diverted by capture of the carbon radical intermediate with oxygen gas (O(2)) to deliver the amide oxygen from O(2). This understanding was used to develop a straightforward protocol for the preparation of (18)O-labeled amides in peptides by simply performing the umpolung amide synthesis reaction under an atmosphere of 18O2.

| S-EPMC3252937 | biostudies-literature

Instability of Amide Bond with Trifluoroacetic Acid (20%): Synthesis, Conformational Analysis, and Mechanistic Insights into Cleavable Amide Bond Comprising β-Troponylhydrazino Acid.

Project description:The instability of an amide bond with dilute trifluoroacetic acid (TFA) is a rare chemical event. The native amide bonds are stable even in the neat TFA, which is one of the reagents that releases the peptides from the solid support in the solid-supported peptide synthesis method. In the repertoire of unnatural peptidomics, α-/β-hydrazino acids and their peptides are explored for the synthesis of N-amino peptide derivatives, and their amide bonds are stable in TFA (∼100%) as natural amide bonds. This report describes the synthesis of a β-hydrazino acid analogue as β-troponylhydrazino acid, containing a nonbenzenoid natural troponyl scaffold. The structural and conformational studies of their hybrid di-/tripeptides with the natural amino acid show that the 2-aminotroponyl residue is involved in hydrogen bonding. Surprisingly, the amide bond of β-troponylhydrazino peptides is cleavable with TFA (∼20%) through the formation of a new heterocyclic molecule N-troponylpyrazolidinone or troponylpyrazolidinone. Tropolone and related compounds are excellent biocompatible chromophores. Hence, β-troponylhydrazino acid could be employed for tuning the peptide structure and considered a promising chromophoric acid-sensitive protecting group of a free amine of amino acids/peptides. It could be applied for the estimation of the free amine group functionality by a UV-vis spectrophotometer.

| S-EPMC7557997 | biostudies-literature

Synthesis of L-cyclic tetrapeptides by backbone amide activation CyClick strategy.

Project description:Cyclic tetrapeptides exhibit high cellular permeability and a wide range of biological properties and thus have gained great interest in the field of medicinal chemistry. We synthesized highly strained 12-membered head to tail cyclic peptides with varying reactive amino acids, without oligomerization using the exclusively intramolecular CyClick chemistry. This occurs by a two-step process involving the low-energy formation of a 15 atom-containing cyclic imine, followed by a chemoselective ring contraction of the peptide backbone generating a highly strained 12 atom-containing cyclic tetrapeptide. This reaction exhibited high substrate scope and generated head to tail cyclic tetrapeptides with varying amino acids at the N-terminus, showing chemoselectivity without the need for side group protection.

| S-EPMC10664817 | biostudies-literature

Oxazoles for click chemistry II: synthesis of extended heterocyclic scaffolds.

Project description:New routes to 2, 4, 5-trisubstituted oxazoles were established whereby the substitution pattern was established by the structure of the starting nonsymmetrical acyloins. 2-Chloromethyl-4, 5-disubstituted oxazoles were prepared by refinements of an earlier described process whereby chloroacetyl esters of symmetrical and non-symmetrical acyloins were cyclized using an ammonium acetate/acetic acid protocol. After substitution is effected, the azide moiety is then installed by substitution under mild conditions. While dibrominated and iodinated phenyloxazoles are required for further synthetic elaboration, the cyclization reaction was found to be very sensitive to the relative positions of the halogens in the starting materials.

| S-EPMC4480780 | biostudies-literature

Gold-catalyzed synthesis of oxazoles from alkynyl triazenes and dioxazoles.

Project description:A gold-catalyzed regioselective [3 + 2] cycloaddition of alkynyl triazenes with 1,2,4-dioxazoles was developed. The triazene group in the products could be replaced to obtain iodo-oxazoles, providing potential transformations to diverse oxazole structures. This protocol features readily available starting materials, mild reaction conditions and scalability. A plausible mechanism involving a nitrene transfer process was proposed.

| S-EPMC9428897 | biostudies-literature

Amide-Functionalized Chalcogen-Bridged Flexible Tetranuclear Rhenacycles: Synthesis, Characterization, Solvent Effect on the Structure, and Guest Binding.

Project description:The synthesis of flexible rhenium(I)-based amide-functionalized chalcogen-bridged tetranuclear metallacycles of general formula [{(CO)3Re(μ-ER)2Re(CO)3}2(μ-L)2] (1-8) was achieved by treating rhenium carbonyl with dialkyl/diaryl chalcogenide (RE-ER; E = S and Se) in the presence of ditopic flexible or semiflexible pyridyl ligand with amide functionality (L = N,N'-bis(4-pyridylcarboxamide)-1,2-ethane (bpce) and N,N'-bis(4-(4-pyridylcarboxamide)phenyl)methane (bpcpm)). Compounds 1-8 were formed by multicomponent self-assembly under one-pot reaction conditions via oxidative addition of dialkyl/diaryl chalcogenide to rhenium carbonyl with pyridyl ligands. The resultant metallacyclophanes were characterized using elemental analyses, infrared, ultraviolet-visible, and NMR spectroscopic techniques. Metallacyclophanes 1-3 and 7 were structurally characterized by single-crystal X-ray diffraction methods. The solvent-induced structural change of flexible tetranuclear metallacyclophane 2 was demonstrated by crystallizing 2 in dichloroethane and dimethylformamide. Molecular recognition capabilities of 2 and 7 were studied with few aromatic compounds containing ethereal linkages.

| S-EPMC6641653 | 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