A green synthetic approach to synthesizing diverse 2-pyridones for their exceptional UV shielding functions

An efficient green synthesis of a wide range of N-nonsubstituted 2-pyridones via thermal multicomponent reactions of 4-oxo-4H-chromene-3-carbaldehydes with malonates and ammonium acetate under catalyst- and solvent-free conditions is described. This reaction proceeds through domino Knoevenagel condensation/Michael addition/ring opening/ring closure reactions. This protocol has several advantages, such as commercial availability, low toxicity, ease of handling, and environmental benignity. The potential application of the synthesized compounds as UV protecting materials was also evaluated.