4-(Succinimido)-1-butane sulfonic acid as a Br?nsted acid catalyst for the synthesis of pyrano[4,3-b

4-(Succinimido)-1-butane sulfonic acid was shown to be anefficient and reusable Br?nsted acid catalyst for the synthesis of pyrano[4,3-b]pyran derivatives using thermal and ultrasonic conditions. The catalyst was prepared by mixing succinimide and 1,4-butanesultone, which is simpler and safer than the preparation of succinimide sulfonic acid. This method has the advantages of high yield, clean reaction, simple methodology, and short reaction time. The catalyst can be recycled without loss of activity.