Sulfonic acid-functionalized phthalimide (SFP) as a highly Efficient catalyst for the synthesis of 4H-pyrano[2,3-c]pyrazole

4H-Pyrano[2,3‐c]pyrazole derivatives are of importance in medicinal chemistry, since they are used as precursors to potential drugs, and indicate different pharmaceuticalactivities, such as anti-inflammatory, antibacterial, anticonvulsant, analgesic, antimicrobial, antifungal, and anticancer properties [1,2]. In recent years, sulfonic acid-containing catalysts have attracted much attention in synthetic organic chemistry. The use of this class of catalysts to promote organic transformations, is associated with various benefits including: (i) enhanced reactivity as well as selectivity, (ii) uncomplicated work-up, (iii) easy accessibility of the starting materials for the catalyst synthesis, (iv) efficiency, (v) environmentally friendly reaction conditions, and (vi) ability to promote a wide range of reactions [3]. In this work, sulfonic acid-functionalized phthalimide (SFP) has been used as a highly efficient catalyst for the reaction of arylaldehydes, malononitrile and 3-methyl-1-phenyl- 2-pyrazolin-5-one under solvent-free conditions to synthesize 4Hpyrano[ 2,3‐c]pyrazoles (Scheme 1). Excellent yields, short reaction times, easy work-up and purification of the products, easy production of the catalyst and relatively mild conditions are some advantages of this procedure