Asymmetric Synthesis of Enantioenriched 2‐Aryl‐2,3‐Dihydrobenzofurans by a Lewis Acid Catalyzed Cyclopropanation/Intramolecular Rearrangement Sequence

A cyclopropanation/intramolecular rearrangement initiated by the Michael addition of in situ generated ortho‐quinone methides (o‐QMs) has been developed for the enantioselective synthesis of 2‐aryl‐2,3‐dihydrobenzofurans containing two consecutive stereogenic centers, including a quaternary carbon a...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2019-09, Vol.58 (38), p.13427-13432
Main Authors: Pandit, Rameshwar Prasad, Kim, Seung Tae, Ryu, Do Hyun
Format: Article
Language:English
Subjects:
2,3-dihydrobenzofuran
Aromatic compounds
Asymmetric synthesis
Catalysts
diazoester
Enantiomers
Lewis acid
ortho-quinone methide
quaternary carbon atoms
Quinones
rearrangement
Stereoselectivity
Synthesis
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Summary:A cyclopropanation/intramolecular rearrangement initiated by the Michael addition of in situ generated ortho‐quinone methides (o‐QMs) has been developed for the enantioselective synthesis of 2‐aryl‐2,3‐dihydrobenzofurans containing two consecutive stereogenic centers, including a quaternary carbon atom. In the presence of a chiral oxazaborolidinium ion catalyst, the reaction proceeded in excellent yields (up to 95 %) with excellent stereoselectivity (up to >99 ee, up to >20:1 d.r.). Getting closure: Excellent yields, diastereoselectivity, and enantioselectivity of 2‐aryl‐2,3‐dihydrobenzofuran derivatives are obtained in the reaction of in situ generated ortho‐quinone methides with α‐diazoester compounds in the presence of a chiral oxazaborolidinium ion catalyst (COBI).
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201906954