One-Pot Multi Component Microwave Assisted Synthesis of 4H-Pyrano [2, 3-c] Pyrazoles in Methanol and their Antibacterial Study

Abstract

Upon literature studies, pyrano-pyrazoles were found to exhibit the biological activity as antimicrobial agents. So literature employed conventional stirring and reflux condensing to afford different pyrano-pyrazoles. Recent researches adopted the Microwave method, which is a simple and convenient method for organic synthesis. In this work, we reported the synthesis of different 4H-pyrano [2, 3-c] pyrazoles via two different methods, such as microwave & conventional stirring at room temperature. Ethyl acetoacetate, hydrazine hydrate, malanonitrile, and different substituted carbonyl compounds were made to react in the presence of methanol solvent & potassium ter-butoxide, a base catalyst. The microwave method was adopted for all the reactions and found to be more potent than the conventional method. The prepared compounds were characterized by FT-IR, 1HNMR, and 13CNMR. These compounds were screened for anti-bacterial activity against Staphylococcus aureus and E. coli by well diffusion method and showed the excellent antibacterial property. Our In vitro test for antibacterial study involves excellent MIC (µg/ml) and zone inhibition (mm) measurements of all synthesized compounds. Microwave irradiation synthesis hastens the reaction and is completed very fast. Potassium ter-butoxide, a base catalyst, is proved to be a good catalyst for accelerating the reactions. The yield of all synthesized compounds was good. Different 4H-pyrano [2, 3-c] pyrazoles exhibited good potency against Staphylococcus aureus and E. coli. In the presence of a base catalyst, the reactions are faster than in the absence of a catalyst. The microwave method is a good methodology for the green syntheses. Derivatives of 4H-pyrano [2, 3-c] pyrazoles exhibited excellent MIC (µg/ml) and proved to be as good antibacterial agents.