1 - SOMO and Photoredox Asymmetric Organocatalysis

Abstract

Asymmetric organocatalysis, together with metal catalysis and biocatalysis, by responding to the concept of Green Chemistry, aims to overcome to the sustainability challenge which our modern society must face over in the forthcoming decades. Accordingly, this particularly important research topic has flourished over the past 15years, as witnessed by the numerous achievements attained so far. From its renaissance at the beginning of the century, this field of research has constantly evolved. While initially dominated by enamine-based processes, the developments of iminium, Brønsted acid, N-heterocyclic carbene (NHC), ion-pairing, and numerous other strategies have allowed the boundaries of this catalytic method to progressively push forward and, thereby, step by step, have made it possible to solve many synthetic bottlenecks. Accordingly, the success of organocatalysis partly comes from its multifaceted nature that has allowed the advent of many different, yet complementary, modes of activation. Lately, the organic synthetic community could not help but notice a number of substantial advances in this field, in which, in opposition to commonly employed polar modes of activations organocatalysis has been merged with radical chemistry. The aim of this chapter is to highlight some of these innovative developments and hopefully demonstrate that, by harnessing the high reactivity of radical species, organocatalysis will definitely play a key role in the future. This review, which will primarily focus on asymmetric transformations, will cover two major radical organocatalytic methods, namely, singly occupied molecular orbital (SOMO) and photoredox organocatalysis.