A green synthesis of isatoic anhydrides from isatins with urea–hydrogen peroxide complex and ultrasound

The oxidation of isatins at room temperature, using the cheap and environmentally friendly urea–hydrogen peroxide complex and ultrasonic irradiation, has been investigated. The ultrasonic irradiation dramatically reduces the reaction time. With easy and reproducible reaction procedures, different isatoic anhydrides were obtained in excellent yield and with high purity.