Efficient and green synthesis of 4H-pyran derivatives under ultrasound irradiation in the presence of K₂CO₃ supported on acidic montmorillonite

Acid-treated montmorillonite coating with K₂CO₃ is used as a catalyst for an efficient, rapid, one-pot synthesis of 4H-pyran derivatives in good yield under ultrasonic irradiation. The catalyst is environmentally benign, easy handling, nontoxic, stable in air, and inexpensive.