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

Molecules

Phuong Hoang Tran²  Hai Ngoc Tran²  Poul Erik Hansen¹  Mai Hoang Ngoc Do²  Thach Ngoc Le² 

[1] Department of Science, Systems and Models, Roskilde University, POB 260, Roskilde DK-4000, Denmark;Department of Organic Chemistry, Faculty of Chemistry, University of Science, Vietnam National University, Ho Chi Minh City 70000, Vietnam; E-Mails:

关键词: Friedel-Crafts acylation;    indole derivatives;    ionic liquids;    metal triflate;    microwave irradiation;   

DOI  :  10.3390/molecules201019605

来源: mdpi

【 摘 要 】

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.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.