Access to Spirocyclized Oxindoles and Indolenines via Palladium-Catalyzed Cascade Reactions of Propargyl Carbonates with 2‑Oxotryptamines and Tryptamines

Reported here are methods for the direct construction of a range of spirocyclized oxindoles and indolenines in good to excellent yields. Specifically, we report the palladium-catalyzed reactions of oxindoles and indoles, both functioning as bis-nucleophiles, with propargyl carbonates to afford spiro...

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Bibliographic Details
Published in:Journal of organic chemistry 2015-05, Vol.80 (10), p.4928-4941
Main Authors: Nibbs, Antoinette E, Montgomery, Thomas D, Zhu, Ye, Rawal, Viresh H
Format: Article
Language:English
Subjects:
Catalysis
Cyclization
Indoles - chemistry
Molecular Structure
Palladium - chemistry
Pargyline - analogs & derivatives
Pargyline - chemistry
Spiro Compounds - chemical synthesis
Spiro Compounds - chemistry
Tryptamines - chemistry
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Summary:Reported here are methods for the direct construction of a range of spirocyclized oxindoles and indolenines in good to excellent yields. Specifically, we report the palladium-catalyzed reactions of oxindoles and indoles, both functioning as bis-nucleophiles, with propargyl carbonates to afford spirocyclic products having an exocyclic double bond on the newly formed ring. The reaction proceeds through a process wherein the first nucleophilic unit on the oxindole or indole reacts with an allenyl-palladium species, formed from oxidative addition of Pd(0) to propargyl carbonates, to generate a π-allyl palladium intermediate that then reacts further with the second nucleophilic component of the oxindole or indole. The cascade process forges two bonds en route to spirocyclized oxindole and indolenine products. The use of chiral phosphines renders the cyclization sequence enantioselective, providing spirocyclic products with modest to good enantioselectivities.
ISSN:0022-3263
1520-6904
DOI:10.1021/acs.joc.5b00277