Comment on “ l -Proline-promoted three-component reaction of anilines, aldehydes and barbituric acids/malononitrile: regioselective synthesis of 5-arylpyrimido[4,5- b ]quinoline-diones and 2-amino-4-arylquinoline-3-carbonitriles in water” by A. Khalafi-Nezhad, S. Sarikhani, E. Shaikhi Shahidzadeh and F. Panahi, Green Chem. , 2012, 14 , 2876