1-Butyl-3-methylimidazolium Hexafluorophosphate

Synthesis of quinolines via Friedländer annulation in an ionic liquid

Typical procedure: A mixture of 2-aminobenzophenone (197 mg), ethyl acetoacetate (169 mg) and CAN (27 mg) in BMIMPF6 (2 mL) ionic liquid is stirred at 60 ºC for 30 min. Subsequently, the reaction mixture is extracted with EtOAc and dried over MgSO4. After filtration, the mixture is concentrated under reduced pressure and the residue is purified by chromatography on silica gel (eluent: hexane/EtOAc = 3/1) to give the desired quinoline (268 mg, 92 %). The remaining ionic liquid is dried at 80 ºC under reduced pressure and reused in subsequent runs.

• R.-S. Hou, H.-M. Wang, I.-J. Kang, H.-D. Du, and L.-C. Chen, Heterocycles, 2010, 81, 689.