Photoredox Catalysis of Iridium(III)‐Based Photosensitizers

This chapter reviews the design principles of photoredox catalysis and the application in organic synthesis. It summaries the most important Ir(III) photoredox method developments, with particular focus on its application to small-molecule synthesis and the integration of other catalytic technologies (organocatalysis, transition metal catalysis). The controlled oxidation of amines by Ru(II) and Ir(III) photoredox catalysts for net reductive transformations or amine functionalization reactions has proven useful. Stephenson and coworkers utilized photoredox catalysis to oxidize para-methoxybenzyl ethers for a general deprotection strategy. This process was proposed to initiate by an oxidative quenching event (Ir(IV/III*)) and bromotrichloromethane. The development of photoredox catalysis has focused on mild radical generation and propagation. The feasibility of generating carbon radicals at room temperature led to early discoveries of dual catalytic methodologies with Ru(II) photocatalysts. Adoption of these methods using Ir photoredox catalysis has afforded more general transformations and a robust overall approach to small-molecule synthesis.