Divergent reaction pathways for one-pot, three-component synthesis of novel 4H-pyrano[3,2-h]quinolines under ultrasound irradiation

• A facile sonochemical reaction utilizing p-TsOH as catalyst were proposed.
• The products are novel 4H-pyrano[3,2-h]quinoline derivatives contains sulfone moiety.
• Our work evidences that sometimes ultrasound irradiations change the reaction path in comparing with silent condition.
• Improvements in rates and yield of reactions are observed under ultrasonic irradiations.
• Improvements in rates and yield of sonicated reactions due to acoustic cavitation phenomenon.

The present paper deal with the multi-component condensation of 8-hydroxy quinoline, aromatic aldehydes, and sulfone derivatives catalyzed by p-toluenesulfonic acid for the synthesis of a series of 4H-pyrano[3,2-h]quinoline derivatives in ethanol under ultrasonic irradiations. We provide a series of quinoline derivatives containing sulfone moiety interesting for biological screening tests. The reactions were carried out under both conventional and ultrasonic irradiation conditions. In general, improvement in rates and yields were observed when reactions were carried out under sonication compared with classical silent conditions. Also, also, sonochemical reaction give different reaction pathway other than silent reaction. These remarkable effects appeared in sonicated reactions can be reasonably interpreted in terms of acoustic cavitation phenomenon. Structures of the products were established on analytical and spectral data.