The use of PPA-Al2O3 in the synthesis of quinoline derivatives under solvent free conditions

In this project, the catalytic activity of alumina supported polyphosphoric acid (PPA-Al2O3) and its primary application as a solid supported heterogeneous catalyst was examined in the synthesis of quinoline derivatives. The quinoline derivatives was synthesized by the condensation of activated methylene compounds with 2-aminobenzopenones under solvent-free conditions at 70 C. The results showed that the catalyst has high activity and a wide range of cyclic and acyclic β –diketones, β -ketoesters and ketones was successfully converted to the corresponding quinoline derivatives in good purity and high yields. Moreover, the catalyst can be easily recovered by filtration and reused at least four times with only slight reduction in its catalytic activity. Some attractive features of this protocol are high yields, short reaction times, simple procedure with an easy work-up, absence of any volatile and hazardous organic solvents. In addition, this catalytic system can act as an active, inexpensive, recoverable and recyclable catalyst.