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.
开发了一种快速且绿色方法,用于
吲哚3-位选择性酰化而无需保护NH位置。该方法基于使用酸酐的Friedel-Crafts酰化反应。经过优化,发现使用催化量的Y(OTf)3和市售
离子液体[BMI]BF4(1-丁基-3-甲基
咪唑四
氟硼酸盐)作为溶剂效果最佳。反应在单模微波辐射下非常短的时间内完成。该催化剂可重复使用多达四次而不会明显损失活性。研究了一系列取代
吲哚作为底物,并合成了十三种新化合物。