A Simple, Effective, Green Method for the Regioselective 3-Acylation of Unprotected Indoles

A fast and green method is developed for regioselective acylation of indoles in the 3-position without the need for protection of the NH position. The method is based on Friedel-Crafts acylation using acid anhydrides. The method has been optimized, and Y(OTf)₃ in catalytic amounts is found to be the...

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Bibliographic Details
Published in:Molecules (Basel, Switzerland) Switzerland), 2015-10, Vol.20 (10), p.19605-19619
Main Authors: Tran, Phuong Hoang, Tran, Hai Ngoc, Hansen, Poul Erik, Do, Mai Hoang Ngoc, Le, Thach Ngoc
Format: Article
Language:English
Subjects:
Acids
Acylation
Catalysis
Friedel-Crafts acylation
Green Chemistry Technology
indole derivatives
Indoles - chemical synthesis
Indoles - chemistry
ionic liquids
metal triflate
microwave irradiation
Microwaves
Molecular Structure
Solvents
Stereoisomerism
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Summary:A fast and green method is developed for regioselective acylation of indoles in the 3-position without the need for protection of the NH position. The method is based on Friedel-Crafts acylation using acid anhydrides. The method has been optimized, and Y(OTf)₃ in catalytic amounts is found to be the best catalyst together with the commercially available ionic liquid [BMI]BF₄ (1-butyl-3-methylimidazolium tetrafluoro-borate) as solvent. The reaction is completed in a very short time using monomode microwave irradiation. The catalyst can be reused up to four times without significant loss of activity. A range of substituted indoles are investigated as substrates, and thirteen new compounds have been synthesized.
ISSN:1420-3049
1420-3049
DOI:10.3390/molecules201019605