Generation and Synthetic Utilization of Radicals through Electro-redox Processes in Organic and Aqueous Medium

Mahanty, Kingshuk (2023) Generation and Synthetic Utilization of Radicals through Electro-redox Processes in Organic and Aqueous Medium. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Kingshuk Mahanty (16RS014)) 16RS014.pdf - Submitted Version Restricted to Repository staff only Download (12MB)

Abstract

The contents of the thesis entitled “Generation and Synthetic Utilization of Radicals through Electro-redox Processes in Organic and Aqueous Medium” have been distributed into 6 chapters based on the consequences of the experimental works done throughout the research tenure. In recent years, synthetic organic chemists have devoted tirelessly to the advancement of new sustainable chemistry to achieve different valuable scaffolds in a greener way. Apart from many classical approaches for the synthesis and functionalization of various bioactive structural motifs, electrochemistry is considered green and could fine-tune the reaction potential to facilitate several complex reactions. So, functionalization and synthesis of several aromatic and heteroaromatic ring structures via environmentally sustainable methods such as electrochemical methods and their further implementations in pharmaceuticals, and agrochemicals industries as well as academia are also in leading attention. Very recently, the focus shifted towards the development of organic reactions in an aqueous medium to develop new synthetic strategies. The very first chapter, Chapter 1 of the thesis represents an overall outline of the electrochemical organic synthesis and its various synthetic strategies to generate several radicals such as sulfonyl radical, trifluoromethyl radical, aryl radical, etc. Chapter 2 demonstrates the electrochemical methods of the generation of sulfonyl radicals. In the first portion of this chapter, sulfonyl radical is utilized to functionalize one of the most important bioactive indazole moieties. In the last part sulfonyl moiety act as a multicomponent reaction precursor to facilitate the synthesis of multi-substituted pyrazole core. Chapter 3 describes the generation of the aryl radical via both oxidative and reductive pathways respectively from aryl diazonium salt and phenyl hydrazine to functionalize the indazole core. This functionalization reaction is facilitated in the metal-free, mediator-free electrochemical condition. Chapter 4 proposed a practical and sustainable way to generate trifluoromethylated radical via metal-free and mediator-free electrochemical conditions. This trifluoromethylated radical is further utilized via cascade cyclization reaction to achieve trifluoromethylated Isoxazoline scaffold. Chapter 5 is focused on the efficient routes for the synthesis of N-sulfonyl amidines and 1,3,4- oxadiazoles through the activation of DMF molecule. Successful implementation of electroredox on dehydrative coupling and oxidative cyclization reactions eliminates the necessity of stoichiometric chemical oxidants and minimizes the generation of reagent waste. In Chapter 6, a highly competent electrochemical strategy for the synthesis of diastereoselective pinacol in an aqueous medium has been described. Remarkably, this efficient transition metal-free reductive electrochemical protocol is well established in an undivided cell without the involvement of organic solvent and sacrificial electrodes. Experimental findings and characterization data of synthesized compounds are documented at the end of each chapter. Moreover, the copies of ¹H and ¹³C NMR spectra of selected new compounds are also involved. Pertinent literature references are cited at the end of the thesis.

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