DEVELOPMENT OF ALIPHATIC C-H FUNCTIONALIZATION REACTIONS UTILIZING ORGANIC PHOTOREDOX CATALYSIS

C-H functionalization has been an invaluable tool for the synthesis of complex molecules within the pharmaceutical industry. Late-stage diversification of molecules via accessing C-H bonds has been sought after and the ability to achieve selective C-H bond functionalization is crucial. Distinguishing between other reactive functional handles, as well as the most abundant bond in nature, is an extraordinary challenge in modern chemical synthesis in which new methodologies are continuously being developed. Photoredox catalysis has been an important facet of reactivity over the past few decades and has seen a wide variety of use within the realm of C-H functionalization. Due to the unique properties of organic photocatalysts, these reagents have promoted access to and control of high energy intermediates that transition metal photoredox catalysts or conventional polar chemistry are unable to access. Additionally, late row transition metal complexes are costly and difficult to synthesize, leading to more sought-after sustainable methods of single electron catalysis. Development of a novel methodology for activating the homoallylic C-H bonds of olefins is described in Chapter 2. This utilizes an established strategy of accessing readily oxidizable intermediates in-situ via tandem photoredox catalysis and cobalt(II) dehydrogenation catalysis. Ultimately, the selectivity of C-H functionalization between the 1,2- vs 1,4-addition adducts remains a challenge with this approach. Further experiments are needed to induce desired reactivity in order to functionalize a C-H bond that is classically difficult to access considering the lability of the allylic C-H bond. A strategy for selective aliphatic C-H functionalization of alcohols is presented in Chapter 3. This concept draws on literature precedent surrounding the photophysical properties of transient aryl sulfoxide cation radical intermediates and their fate over the course of typical reaction conditions. Serendipitously, it was discovered that alkoxy radical generation could be induced through utilization of these high energy species. Described herein is the generation of alkoxy radicals and their subsequent reaction pathways. Chapter 4 delineates the foundation for β-C-H functionalization of alcohols in a manner reminiscent of the previously established alkoxy radical generation methodology. Synthesis of radical mediators in the form of Y=X bonding patterns and their subsequent reactivity are described.