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

Abstract

The title paper reported a green and efficient one-pot method for synthesizing 5-aryl-pyrimido[4,5-b]quinoline-dione derivatives via a three-component reaction involving anilines, aldehydes and barbituric acids. However, these starting materials can theoretically yield two possible structural variants. Under the same reaction conditions as the title paper, the ¹H NMR spectrum of the synthesized compound (4f) provided data that challenge the structural assignment of the proposed target compound.