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The photocatalyzed dearomative reaction between various electron-deficient aromatic compounds and a non-stabilized azomethine ylide is successfully performed in a flow system. Whereas the use of supported eosin as organic photocatalyst exhibits limited efficiency, turning to the soluble Rose Bengal allows to transform a broad range of substrates from hetarenes (indole, benzofuran, quinoline, pyridine) to naphthalenes and benzenes. This photocatalyzed (3+2) dearomative cycloaddition under green light irradiation provides a simple and efficient access to tridimensional pyrrolidino scaffolds with a tetrasubstituted carbon center at ring junction and can be performed in the friendly ethyl acetate. Computational studies support the mechanism involving azomethine ylide as reactive species toward the electron-poor arene.
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http://dx.doi.org/10.1002/chem.202301567 | DOI Listing |
Angew Chem Int Ed Engl
September 2025
University of Regensburg, Department of Organic Chemistry, Universitätsstr. 31, 93053, Regensburg, Germany.
The visible light-mediated copper(II)-catalyzed one-step synthesis of isoxazolines and isoxazoles from readily available ethyl nitroacetate or phenyl nitromethane is reported. The developed protocol eliminates the need for substrate preactivation or additives, and offers an extensive scope of activated and unactivated alkenes and alkynes as coupling partners. Key intermediates for this formal [3 + 2]-cycloaddition are α-nitro radicals generated via photoinduced single-electron oxidation of nitronates, contrasting the generation of such radicals via Cu(I)-photocatalysis by a reductive pathway, which shows a different reaction pattern in the coupling with alkenes.
View Article and Find Full Text PDFACS Omega
May 2025
Centre of Excellence for Research in Sustainable Chemistry, Department of Chemistry, Federal University of São Carlos, São Carlos, São Paulo 13565-905, Brazil.
This work reports the first synthesis of Δ-pyrrolines promoted by visible light under continuous flow, achieved through the formal (3 + 2)-cycloaddition of 2-azirines to enones. A total of 22 examples of trisubstituted Δ-pyrrolines were prepared in only 30 min of residence time, with 41-93% yield and diastereomeric ratios up to 7:3. Furthermore, continuous flow conditions were also effective when chalcones were used as starting materials, leading to the formation of 7 tetrasubstituted pyrroles with an overall yield ranging from 12 to 47%, via a photocatalyzed cycloaddition-oxidation sequence.
View Article and Find Full Text PDFChem Sci
February 2025
State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University Lanzhou 730000 Gansu China
Substantial advancements have been achieved in the field of photocatalytic borylation utilizing 4c-7e Lewis base-boryl radicals. However, the utilization of 3c-5e neutral boryl radicals for C-B bond formation remains relatively underexplored due to their inherent instability. In this study, we successfully demonstrated the direct construction of C-B bonds using sodium tetraarylborate as a key reagent.
View Article and Find Full Text PDFJ Org Chem
September 2024
School of Chemistry and Chemical Engineering, University of South China, Hengyang 421001, China.
FeTiO has emerged as an interesting semiconductor photocatalyst in organic synthesis. We herein describe a visible-light-induced semiheterogeneous strategy for the synthesis of 3-(2-oxoethyl)indolin-2-ones with moderate to good yields and good functional group compatibility using recyclable FeTiO as a photocatalyst and NHPI as a redox catalyst.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
August 2024
CNRS, UMR 6014 COBRA, Univ Rouen Normandie, INSA Rouen Normandie, Normandie Univ, INC3M FR 3038, F-76000, Rouen, France.
A photocatalyzed formal (3+2) cycloaddition has been developed to construct original polysubstituted α-SCF cyclopentanones in a regio- and diastereoselective manner. This building block approach leverages trifluoromethylthio alkynes and branched/linear aldehydes, as readily available reaction partners, in consecutive hydrogen atom transfers and C-C bond formations. Difluoromethylthio alkynes are also compatible substrates.
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