Direct Excitation of Aldehyde to Activate the C(sp2 )-H Bond by Cobaloxime Catalysis toward Fluorenones Synthesis with Hydrogen Evolution.
Angew Chem Int Ed Engl
; 62(7): e202214944, 2023 Feb 06.
Article
em En
| MEDLINE
| ID: mdl-36510781
ABSTRACT
A new way to form fluorenones via the direct excitation of substrates instead of photocatalyst to activate the C(sp2 )-H bond under redox-neutral condition is reported. Our design relies on the photoexcited aromatic aldehyde intermediates that can be intercepted by cobaloxime catalyst through single electron transfer for following ß-H elimination. The generation of acyl radical and successful interception by a metal catalyst cobaloxime avoid the use of a photocatalyst and stoichiometric external oxidants, affording a series of highly substituted fluorenones, including six-membered ketones, such as xanthone and thioxanthone derivatives in good to excellent yields, and with hydrogen as the only byproduct. This catalytic system features a readily available metal catalyst, mild reaction conditions and broad substrate scope, in which sunlight reaction and scale-up experiments by continuous-flow approach make the new methodology sustainable and amenable for potentially operational procedures.
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MEDLINE
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En
Ano de publicação:
2023
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Article