Cascade Synthesis of Diverse Heterocycles

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Jain, Anshul
Rana, Nirmal K.
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Indian Institute of Technology Jodhpur
Heterocycles are the largest and most diversified families of organic compounds. They play significant roles in chemical synthesis as well as in bio-chemistry. Therefore, developing innovative and efficient methodologies for synthesizing multifunctional heterocyclic compounds, with the goal of achieving higher molecular complexity and improved functional group compatibilities from readily available starting materials under mild reaction conditions, is a significant area of today's research. Cascade approaches have long been acknowledged as they provide an admirable collection of strategies and tactics for developing novel and efficient routes with a minimum number of operations for synthesizing complex molecules. These classes of reactions represent not only the multiple bond-forming transformations but also the subsequent reactions in which the functionalities created in the earlier steps are manifested. One-pot approaches are used to increase the overall efficiency of processes by reducing physical efforts well as minimizing the use of solvents and chemicals. On the other hand, the use of supported catalysts/reagents has revolutionized the field of chemistry. The immobilization of the catalyst onto a solid support material prevents its loss during the reaction, increases its surface area, and enhances its selectivity and efficiency. It is an attractive field of research in organic synthesis due to several advantages over traditional catalysts/reagents i.e., simplified product purifications, reusability, reduction of side products, less waste generation, and economic process. These make the process more sustainable and greener as well. In this thesis, the research work encapsulated, is focused on the development of novel and sustainable cascade approaches towards the synthesis of diverse heterocyclic compounds. The thesis is divided into six chapters. Chapter 1 presents the importance of heterocycles and summarized the advancement of organocatalyzed methods towards the construction of diverse heterocycles such as tetrahydrothiophene, ?-pyrones, dihydroindoles and benzoxazoles. Next, we have discussed the objectives, scope and the structure of the thesis. Chapter 2 includes polymer-supported base-catalyzed synthesis of sulfur-containing heterocycles, trisubstituted tetrahydrothiophenes and spiro-thiazolone-tetrahydrothiophenes, via thia-Michael/aldol cascade approach. Chapter 3 deals with the synthesis of oxygen-rich heterocycles, ?-pyrones, through polystyrene-linked DMAP-catalyzed Michael-addition/lactonization/elimination reactions. In chapter 4, nitrogen-containing heterocycles, dihydroindoles, were synthesized utilizing supported-pyridinium ylide and sulfur ylide as a C-1 synthons. Chapter 5 represents the development of novel approach for the construction of 2-aryl benzoxazoles. These compounds seem to have potential activities as agonists for the biogenesis of utrophin. In the last chapter, we have concluded the thesis with future scope
Jain, Anshul. (2023).Cascade Synthesis of Diverse Heterocycles (Doctor's thesis). Indian Institute of Technology Jodhpur, Jodhpur.