The application of visible light mediated photoredox catalysis in organic transformations

Abstract

In the modern era of chemistry, photoredox catalysis has proven its usefulness in many synthetic applications. First of all, with the use of visible-light as the only activation source, several challenging organic transformations now could be successfully carried out at ambient conditions. Secondly, the remarkable redox regulatory capability of photoredox catalysts has facilitated a handful of difficult electron transfer processes, breaking conventional energy barrier by going through alternative pathways. The increasing number of reports on novel bond formation strategies has been ongoing through the last few decades. Therefore, the objective of my thesis is to develop new C-H functionalization methodologies and to probe new chemistry of traditional organic reagents under visiblelight mediated photoredox conditions. The thesis begins with an overview introduction about photoredox catalysis, including catalyst design and photophysical properties, mode of actions and break-through applications in organic synthesis during recent years. Subsequently, chapter 2 describes my work on allylic/benzylic Csp3-H activation for intermolecular cross-radical radical couplings. The reaction outcome resembles Barbier type ketone alkylation for tertiary alcohol synthesis; nevertheless, the use of organometallic nucleophiles or strong reducing metals is avoided. In the next chapter, umpolung chemistry of traditional phosphorus ylide nucleophile was first explored in direct olefin synthesis. Finally, the last chapter concludes my thesis with catalytic aldehyde Csp2-H activation for non-symmetrical ketone synthesis via two separate pathways, namely, olefin radical addition and nickel catalyzed cross-coupling reaction.