Herein, we report an unprecedented skeletal rearrangement reaction of tetrahydro-β-carbolines enabled by copper-catalyzed single-electron oxidative oxygenation, in which H O and O act as oxygen sources to generate a unique 2-hydroxyl-3-peroxide indoline intermediate. The synthetic reactivity of 2-hydroxyl-3-peroxide indoline species was demonstrated by a unique multi-step bond cleavage and formation cascade. Using a readily available copper catalyst under open-air conditions, highly important yet synthetically difficult spiro[pyrrolidone-(3,1-benzoxazine)] products were obtained in a single operation. The synthetic utility of this methodology is demonstrated by the efficient synthesis of the natural products donaxanine and chimonamidine, as well as the 3-hydroxyl-pyrroloindoline scaffold, in just one or two steps.
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http://dx.doi.org/10.1002/anie.202313687 | DOI Listing |
J Phys Chem A
December 2024
Departamento de Química Física y Química Inorgánica, Facultad de Ciencias─I.U. CINQUIMA, Paseo de Belén, 7, 47011 Valladolid, Spain.
The conformational space of 3-chloropropionic acid has been studied under the isolated conditions of a supersonic expansion using Stark-modulated free-jet absorption millimeter-wave and centimeter-wave chirped-pulse Fourier transform microwave spectroscopy techniques. The rotational spectra originating from the three most stable conformers including Cl and Cl isotopologues were observed in both experiments using helium expansion while a partial conformational relaxation involving skeletal rearrangements takes place in an argon expansion. The rotational parameters, geometries, and energy order were determined from the experiment, allowing a comparison with quantum chemical predictions.
View Article and Find Full Text PDFChem Commun (Camb)
December 2024
Institute of Inorganic Chemistry (AOC), Karlsruhe Institute of Technology (KIT), Kaiserstr. 12, 76131, Karlsruhe, Germany.
Cyclononatetraenyl (Cnt) is a nine-membered monoanionic aromatic ligand. Despite its early discovery in 1963, it has been rarely utilised in coordination chemistry, which is mainly due to its large diameter and easy skeletal rearrangement. Only in 2017, the first lanthanide Cnt complex was synthesised, marking the beginning of a new era in organolanthanide chemistry.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
December 2024
Jinan University College of Pharmacy, College of Pharmacy, CHINA.
Highly functionalized xanthenes possess an impressive range of bioactivities and daunting synthetic challenge due to their unique ring systems and stereocenters. Here, we report an unprecedented ketyl radicals-induced skeletal rearrangement reaction of spirodihydrobenzofurans, enabled by zero-valent iron as reducing agents via photoredox catalysis, facilitating the facile preparation of various highly functionalized xanthenes. The features of this protocol include high chemo- and regioselectivity, exceptionally mild conditions, a broad substrate scope, scalability to gram-scale quantities, and consistent delivery of good to excellent yields.
View Article and Find Full Text PDFJ Am Chem Soc
December 2024
Institute of Chemical Research of Catalonia (ICIQ-CERCA), The Barcelona Institute of Science and Technology, Països Catalans 16, 43007 Tarragona, Spain.
A novel platform for the skeletal editing of single C-C bonds via a single-carbon insertion has been developed using diazirines. This strategy involves the photogeneration of arylchlorocarbenes as carbynoid species that undergo site-selective carbene insertion into tertiary C-H bonds and a subsequent Wagner-Meerwein rearrangement promoted by a silver salt. Our skeletal editing strategy based on a formal selective carbyne C-C bond insertion has been demonstrated in six core-to-core conversions, including linear and cyclic benzylic substrates, alkanes and late-stage functionalizations.
View Article and Find Full Text PDFChemistry
December 2024
Organocatalysis Research Group, Institute of Organic Chemistry, HUN-REN Research Centre for Natural Sciences, 2. Magyar tudósok krt., H-1117, Budapest, Hungary.
A concise, bioinspired, and enantioselective synthesis of (-)-hunterine A, an odd 6/7/6/6/5 pentacyclic natural product, is described. The key step in the synthesis of this complex structure is an interim-template directed 6-exo selective epoxide ring-opening reaction, which is interwoven with a hydrolysis step of the indolenine hemiaminal template to create the unusual 7-membered azepine bridge motif. Our work not only refines the previously proposed biogenetic pathway, but also reveals the possible stereochemical prerequisite of the unique skeletal rearrangement, which provides a vantage point for understanding how (-)-hunterine A is likely to be generated in nature.
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