Solvent-Free Synthesis of Chalcones

The solvent-free synthesis of 20 chalcones was carried out by grinding the benzaldehyde (unsubstituted, 4-methyl, 4-methoxy, 3-chloro, or 4-chloro) and the acetophenone (unsubstituted, 4-methyl, 4-bromo, or 4-methoxy) in the presence of solid sodium hydroxide with a mortar and pestle. In general, the chalcones were obtained in high yields and high purity. Minor quantities of ketol and Michael addition product were detected by NMR spectroscopy. These side-products were easily removed by recrystallization. The results seem to indicate a correlation between the success of the solvent-free synthesis and the melting point of the chalcone. Chalcones with relatively high melting points (higher than 80°C) were obtained in high yields. The three chalcones that could not be produced in good yields had relatively low melting points.