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Rhodium(III)‐Catalyzed Asymmetric [4+1] and [5+1] Annulation of Arenes and 1,3‐Enynes: A Distinct Mechanism of Allyl Formation and Allyl Functionalization
Author(s) -
Sun Jiaqiong,
Yuan Weiliang,
Tian Rong,
Wang Peiyuan,
Zhang XuePeng,
Li Xingwei
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202010832
Subject(s) - chemistry , annulation , allylic rearrangement , reductive elimination , nucleophile , enantioselective synthesis , rhodium , agostic interaction , medicinal chemistry , hydride , alkyne , nucleophilic addition , migratory insertion , catalysis , cyclopentadienyl complex , oxidative addition , stereochemistry , organic chemistry , hydrogen , metal
We report chiral Rh III cyclopentadienyl‐catalyzed enantioselective synthesis of lactams and isochromenes through oxidative [4+1] and [5+1] annulation, respectively, between arenes and 1,3‐enynes. The reaction proceeds through a C−H activation, alkenyl‐to‐allyl rearrangement, and a nucleophilic cyclization cascade. The mechanisms of the [4+1] annulations were elucidated by a combination of experimental and computational methods. DFT studies indicated that, following the C−H activation and alkyne insertion, a Rh III alkenyl intermediate undergoes δ ‐hydrogen elimination of the allylic C−H via a six‐membered ring transition state to produce a Rh III enallene hydride intermediate. Subsequent hydride insertion and allyl rearrangement affords several rhodium(III) allyl intermediates, and a rare Rh III η 4 ene‐allyl species with π‐agostic interaction undergoes SN 2 ′‐type external attack by the nitrogen nucleophile, instead of C−N reductive elimination, as the stereodetermining step.