Different Mechanistic Aspects of Photoredox Catalysis and Its Application in Organic Transformations

Abstract

Photoredox catalysis has emerged as a powerful and versatile tool in organic synthesis, enabling diverse chemical transformations that were previously challenging or inaccessible. This thesis explores the principles, applications, and recent advancements in photoredox catalysis to address contemporary challenges in the field of synthetic chemistry. The introductory section provides an overview of the fundamental concepts underlying photoredox catalysis, elucidating the mechanisms involved in light-induced electron transfer processes and their significance in promoting a wide array of organic reactions. Emphasis is placed on the unique ability of photoexcited catalysts to access high-energy intermediates and drive reactions under mild conditions, facilitating the construction of complex molecular architectures with enhanced efficiency and selectivity. Subsequent chapters showcase various protocols developed within photoredox catalysis. One such method demonstrates a versatile protocol for synthesizing α- acyloxy esters and ketones from aldehydes under visible light conditions, highlighting its adaptability to various aldehydes and functional groups, which underscores its broad applicability and robustness. Additionally, a metal-free, chemo-selective hydrogenation method for activated C-C double bonds using visible light exposure is presented. The mechanistic investigation reveals the role of activated double bonds in oxidatively quenching the photocatalyst, employing DIPEA as a sacrificial electron donor. Furthermore, an innovative one- pot synthesis of α-substituted glutaric diesters from readily available aldehydes and acrylates under visible light, without metal catalysts, is introduced. This approach demonstrates tolerance for diverse functional groups and explores the derivatives' versatility in synthesizing biologically relevant compounds. Moreover, solvent-tunable methodologies for synthesizing anthranilic acid derivatives and quinoline derivatives from 2-phenylindole under visible light irradiation, without photocatalysts, are developed. The alcohol-based protocol involves singlet oxygen, while the chloroform-based method forms an electron donor-acceptor (EDA) complex, both activated by light exposure.