Ultrasonication under catalyst-free condition: an advanced synthetic technique toward the green synthesis of bioactive heterocycles

Abstract Application of ultrasound irradiation as an alternative source of energy has attracted an increasing interest in organic synthesis over the last few years. Such an impressive effect of ultrasonication in organic green synthesis is demonstrated in this chapter, focusing on multicomponent reactions aimed to synthesize bioactive heterocyclic compounds in green solvents without the aid of any added catalyst. Use of ambient reactions conditions, green solvents, and no added catalysts are the notable features of the synthetic protocols covered in this chapter toward accessing a diverse range of N-/O-containing heterocyclic scaffolds of biological significance.