SOLVENT FREE MULTICOMPONENT REACTIONS FOR THE SYNTHESIS OF HETEROCYCLIC SCAFFOLDS

Abstract

The central theme of this thesis is designing, synthesis and spectral characterization of synthesized heterocyclic organic compounds containing N, O and/or S atoms in their ring. The thesis highlights novel strategies focusing on sustainable synthesis which were accomplished in the absence of solvent under mechanochemical or microwave irradiation approaches which have been attracting considerable interest in the past few decades and becoming the mainstream route of synthesis in modern organic synthesis. The thesis further illustrates the advantages that an organic chemist render as a result of endowing themselves with the necessary skills emanating from the idea of working principles suggested in green synthesis. The whole thesis is divided into five principal chapters. Chapter-1 is an introduction dealing with the background of the research work and addresses current challenges and objectives of the study. This chapter gives bird’s-eye view of the progress and advancement in mechanochemical and solvent free microwave irradiation based chemical transformations synchronized with the idea of multicomponent reaction (MCRs) approach. Chapter-2 Describes an efficient mechanochemical (- hand grinding) synthesis of pyran fused spirooxindoles under solvent and catalyst free condition. This synthetic strategy showed promising green metrics score at multigram scale synthesis confirming its competency at large scale production. ii Chapter-3 Describes regioselective synthesis of functionalized [1, 3]-thiazine-4-ones via multicomponent click reaction approach under exceptionally green profile. It renders the benefit for fast organic reactions involved in the process of drug discovery over its time taking other combinatorial ways. Chapter-4 Illustrates synergistic collaborative action of solvent free microwave irradiation and mechanochemical approaches for the synthesis of oxindoles-β-enaminones hybrids iii through one pot two-steps mechanochemical four component reaction under solvent and catalyst free condition. Chapter-5 Describes ammonium chloride assisted microwave mediated domino multicomponent reaction: An efficient and sustainable access for the synthesis of quinazolin-4(3H)-imines under solvent free condition. It illustrates the benefit this novel strategy provides with respect to the previously reported work in this area.