Proficient Procedure for Preparation of Quinoline Derivatives Catalyzed by NbCl5 in Glycerol as Green Solvent

Quinolines, an important class of potentially bioactive compounds, have been synthesized by treatment of o-aminoaryl ketones and carbonyl compound utilizing niobium (V) chloride (NbCl5) as an available and inexpensive catalyst. The quinoline derivatives were prepared in glycerol, an excellent solvent in terms of environmental impact, with high yields (76–98%) and short reaction times (20–90 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 that 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.