Synthesis of 1,3-Diphenyl-1H-pyrazole-5-carbonitrile via Multicomponent Reaction

Pyrazole is amongst the most important structural units found in many different natural and synthetic products that exhibit a wide range of biological activities [1]. Thepyrazole core is a privileged heterocyclic scaffold, and is a constituent of agro-chemicals, and polymeric materials, besides its use as a unique ligand. Although pyrazoles are rarely found in natural products, they represent an important motif of man-made biologically active compounds such as celecoxib, fipronil, lonazolac, viagra, and many others. In continuance of our interest in the 1,3-dipolar cycloaddition reactions [2,3] we describe our endeavor toward the synthesis of 1,3-diphenyl pyrazoles on the basis of the 1,3-dipolar cycloaddition protocol. Therefore a straightforward, operationally simple and high yielding protocol for the synthesis of pyrazole derivatives, from easily available starting materials is always needed. Presented in this article are the results of One-Pot , three-component coupling of, 4-oxo-4H-chromene-3- carbaldehyde, hydroxylamine hydrochloride and hydrazonoyl chlorides 1 to yield 1,3,4- trisubstituted pyrazoles 2.We describe a straight forward strategy for the regioselective synthesis of pyrazoles in good to excellent yields in EtOH as solvent at room temperature (Figure 1).