4-（Succinimido）-1-butane sulfonic acid as a Bronsted acid catalyst for synthesis of pyrano[4,3-b]pyran derivatives under solvent-free conditions

4-(Succinimido)-1-butane sulfonic acid as an efficient and reusable Bronsted acid catalyzed the synthesis of pyrano[4,3-b]pyran derivatives under solvent-free conditions.The catalyst can be prepared by mixing succinimide and 1,4-butanesultone that is more simple 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 could be recycled without significant loss of activity.