A novel iminium ion cascade reaction has been developed that allows for the stereoselective synthesis of a variety of substituted aza-fused bicycles. The combination of amino allylsilanes and aldehydes (or ketones) was used to synthesize a number of quinolizidines and indolizidines in an one-pot reaction sequence. This technology has been used to effect the facile syntheses of several indolizidine and quinolizidine natural products including, (±)-epilupinine, (±)-tashiromine, and (-)-epimyrtine. Substrate scope has been examined varying the type of amino allylsilanes (primary, secondary and conjugated) and carbonyl compounds (aldehydes and ketones) to give a variety of fused ring structures. Varying the components chosen allows for the inclusion of synthetically useful functional groups at different positions on the core structure. The methodology has been used to construct the tricyclic core structures present in the cylindricine family and halichlorine.
Download full-text PDF |
Source |
|---|---|
| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2947323 | PMC |
| http://dx.doi.org/10.1016/j.tet.2008.10.074 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Total syntheses of the parvistemoline alkaloids enabled by stereocontrolled Ir/Pd-catalyzed allylic alkylation.
Nat Commun
December 2024
Key Laboratory of Phytochemistry and Natural Medicines, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China.
The functionalized polycycle with densely contiguous tertiary stereocenters is a formidable challenge in synthesizing the parvistemoline family of Stemona alkaloids. We herein report their catalytic, asymmetric total syntheses in 13-14 steps from commercially available 2-(methoxycarbonyl)-pyrrole, featuring the development and deployment of an Ir/Pd-synergistically-catalyzed allylation of α-non-substituted keto esters with secondary aryl-substituted alcohols, stereodivergently accessible to four stereoisomers. Using chiral Pd-enolate and Ir π-allyl complex under neutral conditions, no epimerization occurs.
View Article and Find Full Text PDFTo discriminate amino acid isomers by multiple stage tandem mass spectrometry (MS), the fragmentation of protonated amino acids were investigated by MS with collision-induced dissociation (CID) and density functional theory calculations. The CID of protonated α-amino acids results in a loss of 46 Da, corresponding to HO and CO, and iminium ions appear as resultant fragments. The CID of protonated β-amino acids also produces iminium ions, but the corresponding loss is 60 Da instead of 46 Da.
View Article and Find Full Text PDFIodide Anion Enables a Reductive Cross-Electrophile Coupling for Preparing Tertiary Amines.
Angew Chem Int Ed Engl
November 2024
Institute of Organic Chemistry, University of Vienna, Währinger Straße 38, 1090, Vienna, Austria.
The reducing power of iodide anion is an underexplored property that can be used for the cross-electrophile coupling of organic molecules. Herein we harness this trait for the preparation of tertiary amines through the combination of two simple reagents: an electrophilic-carbon precursor and an iminium iodide in a dual role - both as nitrogen-containing building block and as reducing agent. The underlying mechanism of this new C-C bond-formation paradigm is explored through a combination of experiment and quantum chemical calculations.
View Article and Find Full Text PDFAsymmetric cyclopropanation an electro-organocatalytic cascade.
Chem Commun (Camb)
November 2024
Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, Tallinn 12618, Estonia.
We report an iminium ion-promoted, asymmetric synthesis of cyclopropanes an electrocatalytic, iodine-mediated ring closure. The mild, controlled electrochemical generation of electrophilic iodine species in catalytic quantities prevents organocatalyst deactivation, while also eliminating the need for halogenating reagents, thus simplifying traditional synthetic approaches.
View Article and Find Full Text PDFRing-Opening Reactions of Imidazolidines and Hexahydropyrimidines with Grignard Reagents.
J Org Chem
November 2024
Department of Pharmacy, University of Pisa, Via Bonanno 33, 56126 Pisa, Italy.
We herein report an unprecedented ring-opening of unstrained cyclic aminals such as imidazolidines and hexahydropyrimidines by the use of Grignard and cuprate reagents to give secondary sulfonamides bearing diversely substituted tertiary amines in the β- or γ-position. This synthetic procedure can be carried out in a one-pot fashion without collateral reactions that are commonly associated with sp-organometallic multicomponent Mannich-type reactions, indicating the fundamental role of sulfonamide protection of the second nitrogen atom in the generation of the cyclic aminal and in the ring-opening process. Computational density functional theory (DFT) data point to the formation of a transient iminium ion intermediate, in which the Lewis acidity of the cationic component of the organometallic reagent triggers the ring-opening process by coordination.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!