Biopolymeric Alginic acid: an Efficient Recyclable Green Catalyst for One-Pot, Four-Component Synthesis of Pyrano [2,3-c]pyrazoles

One of the main challenges in medicinal chemistry is the design and synthesis of biologicallyactive molecules. Dihydropyrano[2,3-c]pyrazoles play an essential role as biologically activecompounds and represent an interesting template for medicinal chemistry. Many of thesecompounds are known for their antimicrobial, insecticidal and anti-inflammatory activities.Furthermore, dihydropyrano[2,3-c] pyrazoles show molluscicidal activity, and are identifiedas a screening kit for Chk1 kinase inhibitor. They also find applications as pharmaceuticalingredients and biodegradable agrochemicals [1, 2]. Recently, a very cheap, naturally available(from cell wall of brownalgae), nontoxic, biodegradable and recyclable alginic acidhasbeen found as an efficient heterogeneous biopolymericBrønsted acid catalyst for organictransformation [3]. In continuation of our interest in the application of heterogeneous catalystin organic transformation, we report the simple and efficient procedure for one pot synthesisof pyrano[2,3-c]pyrazole derivatives using aryl aldehydes, ethyl acetoacetate, malononitrile,and phenyl hydrazinein presence ofalginic acid as catalyst under solvent free at 60° C condition(Fig. 1).