Domino Reactions through Metallaphotoredox Catalysis

Abstract: The exploitation of visible light as a cheap and natural source of energy has enabled a renaissance of classical radical chemistry with the development of photoredox catalysis. This resurgence is driven by the emergence of versatile photoredox catalysts, including organocatalysts and transition metal catalysts. Especially, the merger of transition metal catalysis with photoredox catalysis, called metallaphotoredox catalysis by MacMillan, has received considerable attention in both photochemistry and organometallic chemistry in the past decade, impressively expanding the synthetic utility of visible-light photocatalysis. Along with many simple reactions, such as crosscouplings or C-H activations, metallaphotoredox catalysis is particularly suitable to the development of more complex domino processes. Indeed, this green and powerful strategy, evolving through the generation of radical species under especially mild conditions, has led to the discovery of many novel green domino reactions not achievable by using single-catalyst systems. This review collects for the first time the recent developments in the field of dual photoredox and metalcatalyzed domino reactions since 2015, illustrating the diversity of green radical domino reactions that can be performed under mild conditions using this emerging methodology. It demonstrates that these visible-light-driven photoreactions are blooming to become a cheaper, safer, and greener alternative in organic synthesis. These findings pave the way for more sustainable and versatile synthetic methodologies in both academic and industrial settings. Along with precedent reports dealing with metallaphotoredox catalysis, this review is the first to focus specifically on domino reactions. It is divided into five sections, treating successively nickel metallaphotocatalysis, copper metallaphotocatalysis, gold metallaphotocatalysis, cobalt metallaphotocatalysis, and palladium metallaphotocatalysis.