Application of natural phosphate modified with sodium nitrate in the synthesis of chalcones: a soft and clean method

The solid obtained by impregnation of natural phosphate (NP) with a solution of sodium nitrate, followed by calcination at 900 °C, is a strongly basic catalyst that is easily prepared from cheap precursors. The catalytic activity of this solid in the Claisen–Schmidt condensation was studied and high yields were obtained with small amounts of catalyst. The reaction rate depends on the substitution in both benzaldehyde and acetophenone derivatives. The effect of the solvent, as well as the addition of water and ammonium salt, was investigated as well. The catalyst can be easily recovered and efficiently reused.