Cerium Catalyzed Transamidation of Secondary Amides under Ultrasound Irradiation: A Breakthrough in Organic Synthesis

A facile and convenient approach for transamidation of secondary amides using cerium as green catalyst under ultrasonic irradiation has been reported. The method involves initial functionalisation of secondary amide substrates with electron withdrawing COCF3 group to weaken the amide C-N bond, and in second step the activated amide undergoes transamidation with various amines in the presence of cerium catalyst via selective cleavage of C < C- > N bond under ultrasonic irradiation to furnish the transamidated products in good to excellent yields. This method shows a broad scope with respect to both amides and amines including sterically hindered amines. Non-precious, green cerium catalyst and ultrasonication method have been used for the first time to accomplish a challenging secondary amide transamidation under exceptionally mild conditions and short reaction time.