SYNTHESIS OF POTENT ORGANIC ASSEMBLIES THROUGH MULTICOMPONENT REACTIONS

Abstract

Heterocycles containing N, O and S atoms in the ring, generally show promising biological applications. Synthesis of diversified heterocycles are in high demand due to their wide applications. To fulfill the ongoing demand, the main role of a chemist is to supply novel heterocycles which can be further screened to find out their biological and pharmaceutical applications. Multicomponent reactions (MCRs) are turned up to be an efficient synthetic strategy to deliver such structural diverse scaffolds in time and help building up chemical libraries with larger scope. MCRs are recognized as the chemical transformations of more than two components mainly operated in one-pot to construct the desired products. The MCR strategy has several advantages like operational simplicity, higher atom efficiency and diverse scaffolds generation in short reaction time over single step operation. Several tools and techniques are used to develop a MCR protocol however application of mechanochemical hand-grinding and microwave irradiation in developing new MCRs strategies are presented in this chapter to synthesize functionalized heterocycles. Amongst heterocycles, pyrans and spirooxindoles are worth mentioning due to their wide range of biological and medicinal activities. The chapter also includes a brief description of biological importance and several synthesis procedures of pyrans and spirooxindoles. In short, the background of the present research work is highlighted in this chapter. However, the previous literature survey revealed that there is still scope not only in synthesizing novel biologically relevant heterocycles but also in developing greener and efficient methodologies to access diversified scaffolds. Thus, the presented work is focused on developing efficient green synthetic protocols for synthesis of structurally diverse heterocycles like pyrans, spirooxindoles, bis(benzo[f]chromen-3-one), acridione, thioxanthendione, bis(hydroxycyclohex-2-enone), tetrahydroquinazolindione derivatives. ABSTRACT | bbbbb CHAPTER-2 DABCO-Catalysed Green Synthetic Protocol for Novel Pyranochromenone Derivatives In this chapter, DABCO-catalysed liquid-assisted grinding for the synthesis of novel dihydrobenzo[f]pyrano[3,2-c]chromenone derivatives has been described. The reported methodology is simple, facile and mild to construct such multicomponent cascade. The benefits of developed one-pot protocol includes diversified scope, excellent yields and high reaction throughput apart from excellent green matrices scores. CHAPTER-3 Urea-Catalysed Microwave-Assisted Synthesis of Novel Spirooxindole Benzopyrans In this chapter, a urea-catalysed easy and facile microwave-assisted protocol is described to construct spiro-benzo[f]pyranochromenes in higher yields. The use of 1-hydroxy-3H-benzo[f]chromen-3-one as a key reactant in such three-component reaction is reported for the first time to provide such novel multicomponent cascade. The superiority of the reported methodology is the operational simplicity, diversified scope and gram scale synthesis along with very good green matrices scores which highlights the synthesis protocol for industry as well. ABSTRACT | bbbbb CHAPTER-4 Diversity Oriented Synthesis of Bis(benzochromenone) Derivatives In this chapter, microwave-assisted DABCO-catalysed synthesis of bis(benzo[f]chromen-3-one) derivatives are reported. The advantages of the methods is the column free efficient synthesis and mere filtration provides good to excellent yield without using any harsh reagent. ABSTRACT | bbbbb CHAPTER-5 Chemistry of Vinyl Esters as Acetaldehyde Surrogates in Some Common Multicomponent Reactions In this chapter, the applications of vinyl esters as acetaldehyde surrogates in different well-known multicomponent reaction are reported. Use of acetaldehyde is limited in synthetic chemistry due to self-polymerizations or lower stability. In this report, the effective utilization of vinyl esters as acetaldehyde surrogates in different conditions are explored efficiently to obtain biologically potent scaffolds. The reported methodology is quite successful to formulate different derivatives like acridione, thioxanthendione, bis(hydroxycyclohex-2-enone), tetrahydroquinazolindione in moderate to good yield.