A Simple, Effective, Green Method for the Regioselective 3-Acylation of Unprotected Indoles
作者:Phuong Tran、Hai Tran、Poul Hansen、Mai Do、Thach Le
DOI:10.3390/molecules201019605
日期:——
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.