Lewis Acid Catalyzed Reductive Cyclization of 2‐Aryloxybenzaldehydes and 2‐(Arylthio)benzaldehydes to Unsubstituted 9H‐Xanthenes and Thioxanthenes in Diisopropyl Ether

Readily accessible 2‐aryloxybenzaldehydes and 2‐(arylthio)benzaldehydes undergo a sequence of reactions leading to a wide variety of unsubstituted 9H‐xanthenes and thioxanthenes in high yields when heated with a Lewis acid in diisopropyl ether. This reductive cyclization method is compatible with se...

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Bibliographic Details
Published in:Advanced synthesis & catalysis 2021-01, Vol.363 (2), p.532-539
Main Authors: Verma, Shashi Kant, Prajapati, Anamika, Saini, Manoj Kumar, Basak, Ashok K.
Format: Article
Language:English
Subjects:
2-(arylthio)benzaldehyde
2-Aryloxybenzaldehyde
9H-xanthene
Aromatic compounds
Benzaldehyde
chemoselective reduction
Functional groups
hydride transfer
Lewis acid
reductive cyclization
xanthylium ion
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Summary:Readily accessible 2‐aryloxybenzaldehydes and 2‐(arylthio)benzaldehydes undergo a sequence of reactions leading to a wide variety of unsubstituted 9H‐xanthenes and thioxanthenes in high yields when heated with a Lewis acid in diisopropyl ether. This reductive cyclization method is compatible with several important functional groups. The method is also applicable for the selective reductive cyclization of the more electron‐rich aryl ring of a 2,6‐bis(aryloxy)benzaldehyde. The key feature of this transformation is the chemoselective reduction of a transient xanthylium ion in the presence of aldehydic group via intermolecular hydride transfer from diisopropyl ether (solvent).
ISSN:1615-4150
1615-4169
DOI:10.1002/adsc.202000836