A Highly Selective and Efficient Method for the Preparation of Amides from Carboxylic Acids and Amines Using Sodium Hydrogen Sulfate Adsorbed on Silica Gel ？

The formation of amides from carboxylic acids and amines has been catalyzed efficiently with sodium hydrogen sulfate adsorbed on silica gel (NaHSO4.SiO2) at room temperature to give the products in high yields. The conversion carried out under reflux requires less reaction times and forms the products in higher yields. The reaction is highly selective as it has been found that either or both of the substrates should be aliphatic but it is failure when the acid as well as the amine is aromatic. The method has been utilized for the preparation of a natural phenethyl amide derivative and its analogues