Heterogeneous Catalysis for Synthesis of Some Heterocyclic Compounds: Efficient and recoverable Schiff base complexes as heterogeneous catalysts

Transition metal complexes are important in catalysis, materials synthesis, photochemistry, and biological systems. Transition metal complexes also act as a hetero-catalyst in preparing (pyrazole-4-carbonitrile derivatives, polyfunctionalized pyrrole derivatives and Dihydrotetrazolo[1,5-a]pyrimidine derivatives) through a facile one pot reaction by using ultrasonic irradiation. The simple operation, short time reaction (20 min) and high efficiency (97%) were the special advantages of this protocol. Furthermore, this green synthesis strategy was advanced by examination of reusability of catalyst in four consecutive cycles without significant loss in catalytic activity. The new synthesis presented remarkable advantages in terms of safety, simplicity, stability, mild conditions, short reaction time, excellent yields and using H2O solvent. The ultrasonic state increases the rate of organic changes in mild conditions that otherwise require strict pressure and temperature conditions. Ultrasonic irradiation is also used to promote the formation, growth and implosive collapse of bubbles in a liquid by various synthetic reactions.