Improved synthesis of diethyl 2,6-dimethyl-4-aryl-4H-pyran-3,5-dicarboxylate under ultrasound irradiation.

Diethyl 2,6-dimethyl-4-aryl-4H-pyran-3,5-dicarboxylates (1) have been synthesized by the reaction of aryl aldehyde and 1,3-diketone catalyzed by ZnCl(2) under ultrasound irradiation. The effects of changes in the ultrasonic power, temperature, and reaction time are discussed. With the optimized reaction conditions, various aryl aldehydes were used to synthesize 4H-pyrans (1) under the influence of ultrasound irradiation. Compared with the conventional thermal methods, the remarkable advantages of this method are the simple experimental procedure, shorter reaction time and high yield of product.