Regiodivergent Trifluoromethanesulfonic Acid‐Promoted Cycloisomerizations of Ynenamines to Fused Indoles

Trifluoromethanesulfonic acid (TfOH)‐mediated cycloisomerizations were controlled through the choice of the electron‐withdrawing functional group at C3 of indoles to provide pyrrolo[3,2,1‐ij]quinolines and benzo[3,4]azepino[1,2‐a]indoles via 6‐endo‐dig and 7‐endo‐dig cyclizations, respectively. The...

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Bibliographic Details
Published in:Advanced synthesis & catalysis 2019-04, Vol.361 (7), p.1683-1688
Main Authors: Alam, Khyarul, Kim, Jin Gyeong, Kang, Dong Yun, Park, Jin Kyoon
Format: Article
Language:English
Subjects:
Benzo[3,4]azepino[1,2-a]indole
Carbonyl groups
Carbonyls
Cycloisomerization
Functional groups
Indoles
Organic compounds
Pyrrolo[3,2,1-ij]quinoline
Substrates
TfOH
Triflic acid
Ynenamines
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Summary:Trifluoromethanesulfonic acid (TfOH)‐mediated cycloisomerizations were controlled through the choice of the electron‐withdrawing functional group at C3 of indoles to provide pyrrolo[3,2,1‐ij]quinolines and benzo[3,4]azepino[1,2‐a]indoles via 6‐endo‐dig and 7‐endo‐dig cyclizations, respectively. The natures of the different cyclizations could be controlled by tuning the electronic influences; indole substrates with carbonyl groups (such as −CO2Et and −COMe) gave products with six‐membered rings, while substrates with sulfonyl groups (such as −Ts and −Ms) gave products with seven‐membered rings in moderate to good yields. By comparison, electronically‐neutral substituents (such as −Ph and −H) turned out to give seven‐membered products through different mechanism.
ISSN:1615-4150
1615-4169
DOI:10.1002/adsc.201801506