Expeditious synthesis of functionalized tricyclic 4-spiro pyrano[2,3-c]pyrazoles in aqueous medium using dodecylbenzenesulphonic acid as a Brønsted acid–surfactant-combined catalyst

An efficient, three-component, one-pot synthesis of highly functionalized tricyclic 4-spiro pyrano[2,3-c]pyrazoles incorporating medicinally privileged heterocyclic moieties has been developed, which also involves the tandem Knoevenagel/Michael addition reaction followed by dehydrative cyclization of pyrazolone derivatives, cyclic 1,3-diketones and cyclic ketones, catalyzed by dodecylbenzenesulphonic acid (DBSA) as a Bronsted acid–surfactant-combined catalyst in aqueous medium. The catalyst is found to be highly competent in accelerating this reaction that results in a considerable short reaction time, alleviating the need for high thermal energy. Wide substrate scope, high to excellent product yield, operational simplicity, absence of any hazardous organic solvent, mild reaction conditions, a simple work up procedure and easily available starting materials are the salient features of this protocol.