Direct Formation of Amides from Carboxylic Acids and Amines Catalyzed by Niobium(V) Oxalate Hydrate

Abstract A wide range of metal salts and oxides were screened to test the catalytic effect in the formation of amides. A water‐compatible catalyst, Niobium(V) oxalate hydrate, proved the ability to catalyze the direct formation of amides from carboxylic acids and amines with a low catalyst loading of 1% in a 1:1 ratio of acids and amines, with the water removal through azeotropic distillation of toluene/water mixtures, which showed a good atomic economic efficiency. Both aromatic and aliphatic carboxylic acids worked well with primary aliphatic amines in the reaction, however, aniline, as an example of primary aromatic amines, needed more than one equivalent amount to complete the amide formation.