Surface cleaning under combined microwave and ultrasound irradiation: flash synthesis of 4H-pyrano[2,3-c]pyrazoles in aqueous media

A clean, rapid and energy-efficient approach to solid-aqueous heterogeneous reactions was developed utilizing the synergistic effect of microwave and ultrasound irradiation. The dramatic acceleration in reaction rates might be explained by the removal of a passivation coating on the substrate particles and the resultant enhancement in mass and heat transfer.