Synthesis Of Glycoluril Under Ultrasound Irradiation

Ultrasound has been increasingly used in organic synthesis during the last three decades. Compared with traditional methods, ultrasound irradiation can give higher yield, shorter reaction time and milder condition. Some applications of ultrasound in the organic reactions such as oxidation reaction, reduction reaction, condensation reaction, addition reaction and substitution reaction, are summarized recently.A mild and efficient method has been developed using ultrasound irradiation for oxidative cleavage of hydrobenzoin to aromatic aldehyde with ammonium chlorochromate (ACC)/silica gel in dichloromethane. A high yield of 72-99% has been obtained at room temperature within 5 min under ultrasound irradiation.The oxidation of benzoins to the corresponding benzils was carried out in 46-98% yield in CH2Cl2 by ACC/silica gel for 2 h under ultrasound irradiation.Synthesis of the glycolurils catalyzed by potassium hydroxide was carried out in 17-75% yield at 40℃in EtOH for 2-8 h under ultrasound irradiation.Compared to the method using stirring under silent, the main advantages of the present procedure are milder condition and shorter reaction time.