Metal‐triflate‐catalyzed intramolecular Friedel–Crafts acylation of 3‐arylpropanoic and 4‐arylbutanoic acids in triflate‐anion ionic liquids under monomodal microwave irradiation is reported. The environmentally benign synthetic procedure allows the formation of cyclic ketones in good yields within a short reaction time. The catalytic metal triflate in triflate‐anion ionic liquids can be easily recovered and reused several times without significant loss of the catalytic performance.

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Intramolecular Friedel–Crafts acylation of aryl acids is a “green” reaction and environmentally benign, generates some valuable intermediated compounds for pharmaceutical uses. In addition, metal triflates under microwave irradiation are efficient catalysts, solving many problems when using traditional Lewis acids. Gd(OTf)3/[BMI]BF4, a good catalyst for the intramolecular Friedel–Crafts acylation under mild condition with high yield, reduced the reaction time and pollution. Furthermore, Gd(OTf)3 in [BMI]BF4 was easily recovered and reused without significant loss of its activity

The title reaction proceeds with a variety of electron-rich as well as electron-poor aromatic compounds to yield the corresponding benzoylated products in good yield. The catalyst can be recovered and reused up to five times without loss of its activity. -(TRAN, P. H.; HANSEN, P. E.; PHAM, T. T.; HUYNH, V. T.; HUYNH, V. H.; TRAN, T. D. T.; HUYNH, T. V.; LE*, T. N.; Synth. Commun. 44 (2014) 20, 2921-2929, http://dx.