Zn(L-proline)2: A Highly efficient catalyst for the multicomponent synthesis dihydropyrano[2,3-c]pyrazole derivatives.

Dihydropyrano[2, 3-c]pyrazoles have been described as important compounds possessing anticancer, antimicrobial, anti-inflammatory, insecticidal, and molluscicidal activities. It is therefore of interest to develop a method for the synthesis of these compounds without the use of toxic solvents or catalysts and also keep the procedure and work up as simple as possible. Recently zinc has been gaining attention in the field of catalysis in addition to the classical coordination chemistry applications. Nano ZnO in various morphologies and sizes were described to be effective catalysts due to their high surface areas in different organic reactions such as Knoevenagel condensations, synthesis of β – acetamido ketones, and synthesis of coumarines. Zn(L-Proline)2 has been described as a powerful yet mild Lewis acid catalyst in the synthesis of pyrazoles, nitro aldol reactions, and Hantzsch reaction. Herein a method for a one-pot, multicomponent reaction using Zn(L-Proline)2 as the catalysis for the synthesis of dihydropyrano[2,3-c]pyrazoles in aqueous ethanol is described. Our method provides environmentally benign conditions, inexpensive catalysis, and easy work up. All products were fully characterized using IR, 1H-NMR and 13C-NMR spectroscopy. Different features of this reaction will be presented at the symposium.http://opus.ipfw.edu/stu_symp2014/1006/thumbnail.jp