Synthesis of Pyrazoles: A Simple, Convenient and Efficient Approach: Efficient synthesis of β–Keto esters, Pyrazoles and their microbial screening

Description

Pyrazolones are traditionally synthesized by the reaction of beta-keto esters with hydrazine and its derivatives. To date, synthesis of these compounds have been somewhat limited by the available chemistry. The methods available in literature to synthesize beta-keto esters are suffers by the use of carbon dioxide and carbon monoxide sources in presence of Pd or transition metal catalysts, long reaction time, use of excess reagent, inconsistent yield, large quantity of by products (due to self Claisen condensation) and require tedious work up procedures to remove the same. Unfortunately the existing methods not produced the beta-ketoesters of heteroaryl compounds from the heteroaryl esters in good yield. These factors lead us to develop a simple, convenient method to synthesize beta-keto esters which in turn converted into their corresponding pyrazoles. The synthesis of I -oxy/thio substituted beta-keto esters through cross-Claisen condensation which suffers by many draw-backs, also been improved by new methodology. The newly synthesized compounds were subjected to screen their biological activities and the results discussed.