Design and synthesis of piperazine based scaffolds to explore their catalytic and antimicrobial activity

Abstract

The adaptations of bacteria and fungi have continuously resulted in their resistance towards existing antibiotics. There is always a need for new antimicrobial substances, which must be active towards drug-resistant microorganisms. Piperazine derivatives are well-known nitrogen heterocycles that have shown diverse biological activities, specifically antimicrobial activity. Taking an overview of earlier piperazine based antimicrobial scaffolds the present research describes about the design and synthesis of new piperazine based antimicrobial scaffolds and screening of their antimicrobial activities. This research also describes about a new catalytic method for Buchwald Hartwig synthesis of N-aryl piperazine scaffolds, which could be used in discovery of newer potential biological targets. Further, silica supported piperazine had also been studied and reported as a catalyst in prior literature for many organic transformations such as Knoevenagel and aldol condensation reactions. In this research a piperazine based catalyst is also evaluated for the synthesis of biologically important 2-aryl-1H- benzimidazoles. newlineThis research work has been summarized into 6 chapters based on synthesis of piperazine scaffolds and their potential antimicrobial and catalytic activity. Chapter-1 provides a review of Buchwald Hartwig reaction for direct catalytic synthesis of biologically active N-aryl piperazine containing drug substances or potential biologically active compounds. Chapter-2 describes the preparation of a Pd nanoparticle catalyst and its application in Buchwald Hartwig synthesis of N-aryl piperazines. Chapter-3 describes synthesis and antimicrobial activity of twenty two novel 1-(benzo[b]thiophen-4-yl)-4-(2-(oxo,hydroxyl, and fluoro)-2-phenylethyl) piperazine and 1-(benzo[d]isothiazole-3-yl)-4-(2-(oxo, hydroxy, and fluoro)-2-phenylethyl) piperazine derivatives. Chapter-4 describes synthesis and antimicrobial activity of ten novel N-mannich bases of isatin with N-aryl piperazines and their 3,3-difluoro derivatives.