Lewis‐Acid‐Catalysed Reaction of 3‐Hydroxy‐2‐oxindoles with Terminal Alkynes: Synthetic Approaches to the Pyrroloindoline Alkaloids

Lewis‐acid‐catalysed reaction of 3‐hydroxy‐2‐oxindoles with a variety of terminal alkynes has been developed. The key step involves alkylation of 3‐aryl (or) 3‐alkyl, 3‐hydroxyoxindoles with terminal alkyne as π‐electron‐rich system to give a variety of 2‐oxindoles with an all‐carbon quaternary cent...

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Bibliographic Details
Published in:European journal of organic chemistry 2017-06, Vol.2017 (21), p.3078-3091
Main Authors: Kinthada, Lakshmana K., Babu, K. Naresh, Padhi, Dikshaa, Bisai, Alakesh
Format: Article
Language:English
Subjects:
2‐Nitrogen heterocycles
Alkaloids
Alkylation
Alkynes
Aromatic compounds
Carbon
Cyclization
Earth‐abundant metals
Lewis acids
Spiro compounds
Synthesis
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Summary:Lewis‐acid‐catalysed reaction of 3‐hydroxy‐2‐oxindoles with a variety of terminal alkynes has been developed. The key step involves alkylation of 3‐aryl (or) 3‐alkyl, 3‐hydroxyoxindoles with terminal alkyne as π‐electron‐rich system to give a variety of 2‐oxindoles with an all‐carbon quaternary centre. On further extension of this method, a variety of spiro‐2‐oxindoles have been synthesized in high yields. The aforementioned methodology has been used in addressing the cyclotryptamine alkaloids linked with aryl group at the pseudobenzylic position. Lewis‐acid‐catalysed reaction of 3‐hydroxy‐2‐oxindoles with a variety of terminal alkynes has been demonstrated to give2‐oxindoles/spiro‐fused 2‐oxindoles sharing an all‐carbon quaternary centre. This reaction presumably goes through intermediate 2H‐indol‐2‐one, which has been proved via some control experiments.
ISSN:1434-193X
1099-0690
DOI:10.1002/ejoc.201700507