N-Sulfonic acid modified poly(styrene-co-maleic anhydride): an efficient and recyclable solid acid catalyst for the synthesis of a wide range of spiropyrans

N-Sulfonic acid modified poly(styrene-co-maleic anhydride) as a recyclable solid acid catalyst efficiently catalyzed the one-pot three-component synthesis of spiropyran derivatives through a simple, convenient, and cost-effective approach in good yields and selectivity. .