Stereodefined Access to Lactams via Olefin Difunctionalization: Iridium Nitrenoids as a Motif of LUMO-Controlled Dipoles
摘要:
Reported herein is a general platform of a stereodefined access to gamma-lactams via Cp*Ir-catalyzed olefin difunctionalization, where in situ generated Ir-nitrenoid is utilized as a key motif of 1,3-dipoles to enable amido transfer in a syn-selective manner. Computational studies suggested that the stereodefined process can be attributed to the proposed working mode of concerted [3 + 2] cyclization. Frontier molecular orbital (FMO) analysis implied that a low-lying lowest unoccupied molecular orbital (LUMO) of the Ir-imido fragment engages in the olefin interaction. Mechanistic understanding on the nitrene transfer process led us to develop mild catalytic protocols of stereoselective difunctionalization of alkenyl dioxazolones to furnish alpha-(haloalkyl)- or (oxyalkyl)lactam products which are of high synthetic and medicinal utility. Product stereochemistry (threo and erythro) was found to be designated by the olefin geometry (E/Z) of substrates.
Photocatalytic Intramolecular C–H Amination Using <i>N</i>-Oxyureas as Nitrene Precursors
作者:Ryan A. Ivanovich、Dilan E. Polat、André M. Beauchemin
DOI:10.1021/acs.orglett.0c02200
日期:2020.8.21
Nitrenes are remarkable high-energy chemical species that enable direct C–N bond formation, typically via controlled reactions of metal-stabilized nitrenes. Here, in contrast, the combined use of photocatalysis with careful engineering of the precursor enabled C–H amination forming imidazolidinones and related nitrogen heterocycles from readily accessible hydroxylamine precursors. Preliminary mechanistic
Repurposing the 3‐Isocyanobutanoic Acid Adenylation Enzyme SfaB for Versatile Amidation and Thioesterification
作者:Mengyi Zhu、Lijuan Wang、Jing He
DOI:10.1002/anie.202010042
日期:2021.1.25
molecules with novel skeletons, but also to identify the enzymes that catalyze diverse chemical reactions. Exploring the substrate promiscuity and catalytic mechanism of those biosynthetic enzymes facilitates the development of potential biocatalysts. SfaB is an acyladenylate‐forming enzyme that adenylates a unique building block, 3‐isocyanobutanoic acid, in the biosynthetic pathway of the diisonitrile
A rhodium-catalyzed C−H amidation/cyclization sequence provides benzothiadiazine-1-oxides from sulfoximines and 1,4,2-dioxazol-5-ones in good yields. The reaction is characterized by a high functional group tolerance and, in contrast to most previous transformations of this type, is well-suited for S-alkyl-S-aryl-substituted sulfoximines.
Ring-Rearrangement Metathesis of Nitroso Diels-Alder Cycloadducts
作者:Guillaume Vincent、Cyrille Kouklovsky
DOI:10.1002/chem.201002558
日期:2011.3.1
various ring sizes, which contain a NO bond. These scaffolds are of synthetic relevance for the generation of molecular diversity and to the total synthesis of alkaloids. The observation of unexpected reactions, such as epimerization or one‐carbon homologation of the alkene side chain, is also reported.
Tethered Aminohydroxylation (TA) Reaction of Amides
作者:Timothy J. Donohoe、Cedric K. A. Callens、Amber L. Thompson
DOI:10.1021/ol900631y
日期:2009.6.4
The first examples of amide-tethered aminohydroxylationreactions, catalyzed by osmium, showing that the use of N−O-based reoxidants are essential for success, are reported. The system that is described is compatible with a variety of different alkene substitution patterns and ring sizes and works with low loadings in both cyclic and acyclic systems. The levels of diastereoselectivity that were observed