Convenient ultrasound-mediated synthesis of 1,4-diazabutadienes under solvent-free conditions

An ultrasound-assisted preparation of 1,4-diazabutadienes via smooth condensation of diketones with amines under solvent-free conditions is described. The generality of this method was examined by the synthesized N,N′-diaryl- and N,N′-dialkyl-1,4-diazabutadiene derivatives. In addition to experimental simplicity, the main advantages of the procedure are mild conditions, short reaction time (2–15 min) and high yields (71–98%).