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Open AccessArticle

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

1
Department of Organic Chemistry, Faculty of Chemistry, University of Science, Vietnam National University, Ho Chi Minh City 70000, Vietnam
2
Department of Science, Systems and Models, Roskilde University, POB 260, Roskilde DK-4000, Denmark
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Author to whom correspondence should be addressed.
Academic Editor: Jason P. Hallett
Molecules 2015, 20(10), 19605-19619; https://doi.org/10.3390/molecules201019605
Received: 5 October 2015 / Revised: 22 October 2015 / Accepted: 22 October 2015 / Published: 27 October 2015
(This article belongs to the Special Issue Ionic Liquids in Organic Synthesis)
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. View Full-Text
Keywords: Friedel-Crafts acylation; indole derivatives; ionic liquids; metal triflate; microwave irradiation Friedel-Crafts acylation; indole derivatives; ionic liquids; metal triflate; microwave irradiation
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MDPI and ACS Style

Tran, P.H.; Tran, H.N.; Hansen, P.E.; Do, M.H.N.; Le, T.N. A Simple, Effective, Green Method for the Regioselective 3-Acylation of Unprotected Indoles. Molecules 2015, 20, 19605-19619.

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