New Concepts in Catalysis: The Development of Photoredox Catalysis as a Powerful Synthetic Tool

Abstract

In the last half-century few developments have changed the chemical community more than the development of novel forms of catalysis. As a result of the powerful impact catalysis has had, there has been an enormous amount of interest in the development of novel forms of catalysis, as each advance has the power to change the way chemists think about constructing complex molecular architectures. The design of novel catalytic activation modes has been a major focus of the MacMillan group since its inception in 1998. Of particular note is the recent advent of the field of photoredox catalysis as a powerful way of activating organic molecules.

The growth of organocatalysis as a general catalysis platform has enabled the development of a large number of new reactions, often in an enantioselective fashion. A method is discussed herein that combines the power of organocatalysis for aldehyde α- activation; a synergistic merger with photoredox catalysis allows for a highly efficient and enantioselective α-cyanoalkylation reaction. The remainder of this thesis discusses the potential of a relatively new field known as metallaphotoredox catalysis. This field couples the utility of transition metal catalysis with the ability of photoredox catalysis to generate highly reactive alkyl radicals under mild conditions. A cross-coupling between sp3 nucleophiles and sp2 electrophiles is presented that utilizes the reactivity of each of these catalytic activation modes. Finally, an entirely novel mode of catalytic activation is presented that allows for the coupling of carboxylic acids with aryl halides.