Efficient procedure for the synthesis of quinoline derivatives by NbCl5.PEG and NbCl5 in glycerol as green solvent

Quinolines, an important class of potentially bioactive compounds, have been synthesized by treatment of O-aminoarylketones and carbonyl compounds utilizing niobium (V) chloride / polyethylenglycole(NbCl5.PEG) and niobium(V)chloride (NbCl5) as available and inexpensive catalysts. The quinoline derivatives were prepared in glycerol, an excellent solvent in terms of environmental impact, with high yields (76-98%) and short reaction times (15- 90 min). Not only diketones but also ketones afforded the desired products in good to excellent yields. The reaction time of 2-amino-5-chlorobenzophenone and dicarbonyl compounds was longer than those of 2-aminobenzophenone. The reaction of cyclic diketones took place faster than open chain analogues. These reactions also proceeded with acetophenone derivatives. In these cases the reaction times are longer.