Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Diastereoselectivity in the Staudinger reaction of pentafluorosulfanylaldimines and ketimines.

ABSTRACT: ?-Lactams were diastereoselectively formed by the reaction of SF5-containing aldimines, or an SF5-containing ketimine, with benzyloxyketene in a conrotatory ring closure process. Imine formation and cyclization were possible in spite of the acidification of protons on the carbon bound to SF5. The reactions of the aldimines demonstrated very good 1,2-lk diastereoselectivity, however lack of stereochemical control of the C-N ketimine geometry was reflected in the stereochemistry of the product ?-lactam. Cyclization of imines with a stereogenic center bearing SF5 was reflected in the 1,2-lk,lk selectivity of the ?-lactam.

SUBMITTER: Penger A

PROVIDER: S-EPMC3869290 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Diastereoselectivity in the Staudinger reaction of pentafluorosulfanylaldimines and ketimines.

Penger Alexander A von Hahmann Cortney N CN Filatov Alexander S AS Welch John T JT

Beilstein journal of organic chemistry 20131127

β-Lactams were diastereoselectively formed by the reaction of SF5-containing aldimines, or an SF5-containing ketimine, with benzyloxyketene in a conrotatory ring closure process. Imine formation and cyclization were possible in spite of the acidification of protons on the carbon bound to SF5. The reactions of the aldimines demonstrated very good 1,2-lk diastereoselectivity, however lack of stereochemical control of the C-N ketimine geometry was reflected in the stereochemistry of the product β-l ...[more]

PMID: 24367432

Similar Datasets

Perfluoroaryl Azide Staudinger Reaction: A Fast and Bioorthogonal Reaction.

Project description:We report a fast Staudinger reaction between perfluoroaryl azides (PFAAs) and aryl phosphines, which occurs readily under ambient conditions. A rate constant as high as 18?m-1 ?s-1 was obtained between methyl 4-azido-2,3,5,6-tetrafluorobenzoate and methyl 2-(diphenylphosphanyl)benzoate in CD3 CN/D2 O. Furthermore, the iminophosphorane product was stable toward hydrolysis and aza-phosphonium ylide reactions. This PFAA Staudinger reaction proved to be an excellent bioothorgonal reaction. PFAA-derivatized mannosamine and galactosamine were successfully transformed into cell-surface glycans and efficiently labeled with phosphine-derivatized fluorophore-conjugated bovine serum albumin.

| S-EPMC5693246 | biostudies-literature

Synthesis of 1,3-diaryl-spiro[azetidine-2,3'-indoline]-2',4-diones via the Staudinger reaction: cis- or trans-diastereoselectivity with different addition modes.

Project description:A new synthetic approach for realizing biologically relevant bis-aryl spiro[azetidine-2,3'-indoline]-2',4-diones was developed based on Staudinger ketene-imine cycloaddition through the one-pot reaction of substituted acetic acids and Schiff bases in the presence of oxalyl chloride and an organic base. A series of [azetidine-2,3'-indoline]-2',4-diones were synthesized using this method. For comparison, the same compounds were obtained using a known technique, where ketene is generated from pre-synthesized acyl chloride. It was shown that the use of oxalyl chloride for ketene generation in the one-pot reaction at room temperature allows for the reversal of the diastereoselectivity of spiro-lactam formation, unlike previously described procedures.

| S-EPMC9051608 | biostudies-literature

Diastereoselectivity on Intramolecular Alder-ene Reaction of 1,6-Dienes.

Project description:A detailed computational study of the intramolecular Alder-ene reaction of different 1,6-dienes at M06-2X(PCM)/TZ2P level of theory has been performed. We want to understand the influence of enophile-geminal substitution pattern in the cis : trans selectivity of the cyclization process. Our analysis of the reaction coordinate by means of activation strain model of chemical reactivity (ASM-distortion interaction model) reveals that the cis-selectivity observed for unactivated reagents is related with high stabilizing orbital interaction and lower strain energy, consequence of an early transition structure. On the other hand, the presence of activating groups increases the asynchronicity of the transition structures and reduces the activation barrier due to more stabilizing orbital and electrostatic interactions, favoring trans-selectivity.

| S-EPMC10087545 | biostudies-literature

Phytophenol Dimerization Reaction: From Basic Rules to Diastereoselectivity and Beyond.

Project description:Phytophenol dimerization, which is a radical-mediated coupling reaction, plays a critical role in many fields, including lignin biosynthesis. To understand the reaction, 2,2-diphenyl-1-picrylhydrazyl radical was used to initiate a series of phytophenol dimerization reactions in methanol. The products were identified using ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC-ESI-Q-TOF-MS/MS) analysis in situ. The identified products mainly included biphenols, magnolol, honokiol, gingerol 6,6'-dimers, 3,6-dimethoxylcatechol β,β' dimer, euphorbetin, bis-eugenol, dehydrodiisoeugenol, trans-ε-viniferin, (+) pinoresinol, and (-) pinoresinol. Structure-function relationship analysis allowed four basic rules to be defined: meta-excluded, C-C bonding domination, ortho-diOH co-activation, and exocyclic C=C involvement. The exocyclic C=C involvement, however, required conjugation with the phenolic core and the para-site of the -OH group, to yield a furan-fused dimer with two chiral centers. Computational chemistry indicated that the entire process was completed via a radical coupling reaction and an intramolecular conjugate addition reaction. Similar results were also found for the horseradish peroxidase (HRP)-catalyzed coniferyl alcohol dimerization, which produced (+) and (-) pinoresinols (but no (-) epipinoresinol), suggesting that the HRP-catalyzed process was essentially an exocyclic C=C-involved phytophenol dimerization reaction. The reaction was highly diastereoselective. This was attributed to the intramolecular reaction, which prohibited Re-attack. The four basic rules and diastereoselectivity can explain and even predict the main products in various chemical and biological events, especially oxidase-catalyzed lignin cyclization.

| S-EPMC9369853 | biostudies-literature

Catalytic Diastereo- and Enantioselective Vinylogous Mannich Reaction of Alkylidenepyrazolones to Isatin-Derived Ketimines.

Project description:A valuable organocatalytic vinylogous Mannich reaction between alkylidenepyrazolones and isatin-derived ketimines has been successfully established. Squaramide organocatalyst, prepared from quinine, catalyzed the diastereo- and enantioselective vinylogous Mannich addition, affording a range of aminooxindole-pyrazolone adducts (24 examples) with excellent outcomes: up to 98% yield with complete diastereoselectivity and excellent enantioselectivity (up to 99% ee). Additionally, different synthetic transformations were performed with the chiral pyrazolone-oxindole adducts.

| S-EPMC8491163 | biostudies-literature

Catalytic Asymmetric Staudinger-aza-Wittig Reaction for the Synthesis of Heterocyclic Amines.

Project description:Many natural products and medicinal drugs are heterocyclic amines possessing a chiral quaternary carbon atom in their heterocyclic ring. Herein, we report the first catalytic and asymmetric Staudinger-aza-Wittig reaction for the desymmetrization of ketones. This highly enantioselective transformation proceeds at room temperature to provide high yields-even on multigram scales-of nitrogen heterocycles featuring a chiral quaternary center. The products of this reaction are potential precursors for the synthesis of pharmaceuticals. A commercially available small P-chiral phosphine catalyst, HypPhos, induces the asymmetry and is recycled through in situ reduction of its oxide, mediated by phenylsilane in the presence of a carboxylic acid. The efficiency, selectivity, scalability, mild reaction conditions, and broad substrate scope portend that this process will expedite the syntheses of chiral heterocyclic amines of significance to chemistry, biology, and medicine.

| S-EPMC7371345 | biostudies-literature

Formation of the BC ring system of upenamide via a Staudinger/aza-Wittig reaction.

Project description:The BC ring system of upenamide was assembled using a stereoselective Diels-Alder reaction followed by a Staudinger/aza-Wittig/imine hydrolysis reaction. Stereoselective aldol coupling with an aldehyde that incorporates the DE ring system led to an advanced synthetic intermediate en route to the marine alkaloid upenamide.

| S-EPMC2534099 | biostudies-literature

Synthesis of Carbohydrate-Grafted Glycopolymers Using a Catalyst-Free, Perfluoroarylazide-Mediated Fast Staudinger Reaction.

Project description:Glycopolymers have gained increasing importance in investigating glycan-lectin interactions, as drug delivery vehicles and in modulating interactions with proteins. The synthesis of these glycopolymers is still a challenging and rigorous exercise. In this regard, the highly efficient click reaction, copper (I)-catalyzed alkyne-azide cycloaddition, has been widely applied not only for its efficiency but also for its tolerance of the appended carbohydrate groups. However, a significant drawback of this method is the use of the heavy metal catalyst which is difficult to remove completely, and ultimately toxic to biological systems. In this work, we present the synthesis of carbohydrate-grafted glycopolymers utilizing a mild and catalyst-free perfluorophenyl azide (PFPA)-mediated Staudinger reaction. Using this strategy, mannose (Man) and maltoheptaose (MH) were grafted onto the biodegradable poly(lactic acid) (PLA) by stirring a PFAA-functionalized PLA with a phosphine-derivatized Man or MH in DMSO at room temperature within an hour. The glycopolymers were characterized by ¹H-NMR, 19F-NMR, 31P-NMR and FTIR.

| S-EPMC6337264 | biostudies-literature

Role of imine isomerization in the stereocontrol of the Staudinger reaction between ketenes and imines.

Project description:Computational-experimental analysis has allowed determining that the stereochemistry of the Staudinger reaction between ketenes and imines is strongly associated with the nature of the imine, which affects the two steps of the reaction. The first step, namely the nucleophilic attack of the sp2-hybridized nitrogen atom of the imine on the sp-hybridized carbon atom of the ketene, is affected by the energetically accessible in situ isomerization patterns of the imine. The second step consists of a conrotatory electrocyclization of the zwitterionic intermediate formed in the previous step. This latter pericyclic step depends on the inward/outward torquoelectronic effects generated by the substituents of the imine. The impact of these factors on the stereochemistry of this reaction has been analyzed kinetically by numerical methods. The results of these simulations are compatible with the experimental results and support these conclusions.

| S-EPMC8978721 | biostudies-literature

Guanidine-Amide-Catalyzed Aza-Henry Reaction of Isatin-Derived Ketimines: Origin of Selectivity and New Catalyst Design.

Project description:Density functional theory (DFT) calculations were performed to investigate the mechanism and the enantioselectivity of the aza-Henry reaction of isatin-derived ketimine catalyzed by chiral guanidine-amide catalysts at the M06-2X-D3/6-311+G(d,p)//M06-2X-D3/6-31G(d,p) (toluene, SMD) theoretical level. The catalytic reaction occurred via a three-step mechanism: (i) the deprotonation of nitromethane by a chiral guanidine-amide catalyst; (ii) formation of C-C bonds; (iii) H-transfer from guanidine to ketimine, accompanied with the regeneration of the catalyst. A dual activation model was proposed, in which the protonated guanidine activated the nitronate, and the amide moiety simultaneously interacted with the ketimine substrate by intermolecular hydrogen bonding. The repulsion of CPh3 group in guanidine as well as N-Boc group in ketimine raised the Pauli repulsion energy (∆EPauli) and the strain energy (∆Estrain) of reacting species in the unfavorable si-face pathway, contributing to a high level of stereoselectivity. A new catalyst with cyclopropenimine and 1,2-diphenylethylcarbamoyl as well as sulfonamide substituent was designed. The strong basicity of cyclopropenimine moiety accelerated the activation of CH3NO2 by decreasing the energy barrier in the deprotonation step. The repulsion between the N-Boc group in ketimine and cyclohexyl group as well as chiral backbone in the new catalyst raised the energy barrier in C-C bond formation along the si-face attack pathway, leading to the formation of R-configuration product. A possible synthetic route for the new catalyst is also suggested.

| S-EPMC8037019 | 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