Browse
Submit Data
Databases
API
Help

Dataset Information

32 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Stereoselective [2,3]-sigmatropic rearrangements of unstabilized nitrogen ylides.

ABSTRACT: The steric course of the [2,3]-rearrangement of several unstabilized nitrogen ylides has been investigated. The reactions proceed cleanly through an anti transition state, affording modest to good yields of a single diastereomer of the product. In two examples containing an N-cinnamyl group, a competing [1,2]-rearrangement affords a minor product.

SUBMITTER: Gawley RE

PROVIDER: S-EPMC2518686 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Dynamics and a unified understanding of competitive [2,3]- and [1,2]-sigmatropic rearrangements based on a study of ammonium ylides.

Project description:The [2,3]- and [1,2]-sigmatropic rearrangements of ammonium ylides are studied by a combination of experimental, standard computational, and dynamic trajectory methods. The mixture of concerted [2,3] rearrangement and bond cleavage observed experimentally is accounted for by the outcome of trajectories passing through the formal [2,3] rearrangement transition state. In this way the bond cleavage is promoted by the pericyclic stabilization of the [2,3] transition state. It is proposed that this dynamic effect is responsible for the pervasive co-occurrence of the two rearrangements.

| S-EPMC3971961 | biostudies-literature

Unstabilized azomethine ylides for the stereoselective synthesis of substituted piperidines, tropanes, and azabicyclo[3.1.0] systems.

Project description:Acid treatment of densely substituted 2-silyl-1,2-dihydropyridines provides a new and convenient entry to reactive azomethine ylides that can (1) be protonated and reduced with high stereoselectivity to give piperidines, (2) participate in [3 + 2] dipolar cycloaddition to give tropanes, and (3) undergo a Nazarov-like 6-? electrocyclization that upon reduction give 2-azabicyclo[3.1.0] systems.

| S-EPMC3586708 | biostudies-literature

Copper-Catalyzed Enantio-, Diastereo-, and Regioselective [2,3]-Rearrangements of Iodonium Ylides.

Project description:The first highly enantioselective, diastereoselective, and regioselective [2,3]-rearrangement of iodonium ylides has been developed as a general solution to catalytic onium ylide rearrangements. In the presence of a chiral copper catalyst, substituted allylic iodides couple with ?-diazoesters to generate metal-coordinated iodonium ylides, which undergo [2,3]-rearrangements with high selectivities (up to >95:5 r.r., up to >95:5 d.r., and up to 97?% ee). The enantioenriched iodoester products can be converted stereospecifically into a variety of onium ylide rearrangement products, as well as compounds that are not accessible by classical onium ylide rearrangements.

| S-EPMC5674996 | biostudies-literature

Catalytic Enantioselective [2,3]-Rearrangements of Allylic Ammonium Ylides: A Mechanistic and Computational Study.

Project description:A mechanistic study of the isothiourea-catalyzed enantioselective [2,3]-rearrangement of allylic ammonium ylides is described. Reaction kinetic analyses using 19F NMR and density functional theory computations have elucidated a reaction profile and allowed identification of the catalyst resting state and turnover-rate limiting step. A catalytically relevant catalyst-substrate adduct has been observed, and its constitution elucidated unambiguously by 13C and 15N isotopic labeling. Isotopic entrainment has shown the observed catalyst-substrate adduct to be a genuine intermediate on the productive cycle toward catalysis. The influence of HOBt as an additive upon the reaction, catalyst resting state, and turnover-rate limiting step has been examined. Crossover experiments have probed the reversibility of each of the proposed steps of the catalytic cycle. Computations were also used to elucidate the origins of stereocontrol, with a 1,5-S···O interaction and the catalyst stereodirecting group providing transition structure rigidification and enantioselectivity, while preference for cation-π interactions over C-H···π is responsible for diastereoselectivity.

| S-EPMC5374492 | biostudies-literature

Ligand-Controlled Regiodivergence in the Copper-Catalyzed [2,3]- and [1,2]-Rearrangements of Iodonium Ylides.

Project description:Despite the importance of allylic ylide rearrangements for the synthesis of complex molecules, the catalyst control of [2,3]- and [1,2]-rearrangements remains an unsolved problem. We developed the first regiodivergent [2,3]- and [1,2]-rearrangements of iodonium ylides that are controlled by copper catalysts bearing different ligands. In the presence of a 2,2'-dipyridyl ligand, diazoesters and allylic iodides react via a [2,3]-rearrangement pathway. Alternatively, a phosphine ligand favors the formation of the [1,2]-rearrangement product. A series of ?-iodoesters containing a broad range of functional groups were obtained in high yields, regioselectivities, and diastereoselectivities. Deuterium-labeling studies suggest distinct mechanisms for the regioselective rearrangements.

| S-EPMC5937265 | biostudies-literature

Ring Expansion of Bicyclic Methyleneaziridines via Concerted, Near-Barrierless [2,3]-Stevens Rearrangements of Aziridinium Ylides.

Project description:The synthesis of densely functionalized azetidinesin a highly stereocontrolled manner is challenging, but interest in the bioactivities of these small heterocycles has stimulated methods for their preparation. We recently reported a one-carbon ring expansion of bicyclic methylene aziridines under dirhodium catalysis capable of delivering enantioenriched azetidines. This work explores this ring expansion using computational and experimental studies. DFT computations indicate that the reaction proceeds through formation of an aziridinium ylide, which is precisely poised for concerted, asynchronous ring-opening/closing to deliver the azetidines in a [2,3]-Stevens-type rearrangement. The concerted nature of this rearrangement is responsible for the stereospecificity of the reaction, where axial chirality from the initial allene substrate is transferred to the azetidine product with complete fidelity. The computed mechanistic pathway highlights the key roles of the olefin and the rigid structure of the methylene aziridine in differentiating our observed ring expansion from competing cheletropic elimination pathways noted with ylides derived from typical aziridines.

| S-EPMC6173328 | biostudies-literature

Highly stereoselective C-C bond formation by rhodium-catalyzed tandem ylide formation/[2,3]-sigmatropic rearrangement between donor/acceptor carbenoids and chiral allylic alcohols.

Project description:The tandem ylide formation/[2,3]-sigmatropic rearrangement between donor/acceptor rhodium carbenoids and chiral allyl alcohols is a convergent C-C bond forming process, which generates two vicinal stereogenic centers. Any of the four possible stereoisomers can be selectively synthesized by appropriate combination of the chiral catalyst Rh(2)(DOSP)(4) and the chiral alcohol.

| S-EPMC3413634 | biostudies-literature

Synthesis of Spirobicyclic Pyrazoles by Intramolecular Dipolar Cycloadditions/[1s, 5s] Sigmatropic Rearrangements.

Project description:The formation of fused pyrazoles via intramolecular 1,3-dipolar cycloadditions of diazo intermediates with pendant alkynes is described. A subsequent thermal [1s, 5s] sigmatropic shift of these pyrazole systems resulted in a ring contraction, forming spirocyclic pyrazoles. The limitations of this rearrangement were explored by changing the substituents on the nonmigrating aromatic ring and by using substrates lacking an aromatic linkage to the propargyl group.

| S-EPMC6955098 | biostudies-literature

Oxyanionic sigmatropic rearrangements relevant to cyclooctadienone formation in penostatins I and F.

Project description:The results of several experiments designed to probe the energetic viability of a reaction path for generation of penostatins I (3) and F (4) via spontaneous [3,3]-sigmatropic rearrangement are reported. In particular, the enolate derived from the 2-vinyl-6-acyldihydropyran 8-cis gave cyclooctadienone 12 via facile anionic oxy-Claisen rearrangement, demonstrating the feasibility of such an event.

| S-EPMC3501534 | biostudies-literature

Mechanistic studies on Au(I)-catalyzed [3,3]-sigmatropic rearrangements using cyclopropane probes.

Project description:A comparative study of the Au(I)-catalyzed [3,3]-sigmatropic rearrangement of propargylic esters and propargyl vinyl ethers is described. Stereochemically defined cyclopropanes are employed as mechanistic probes to provide new synthetic and theoretical data concerning the reversibility of this type of rearrangement. Factors controlling the structure-reactivity relationship of Au(I)-coordinated allenes have been examined, thereby allowing for controlled access to orthogonal reactivity.

| S-EPMC2666792 | 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