Light-Induced Domino and Multicomponent Reactions: How to Reach Molecular Complexity without a Catalyst

Achieving high molecular complexity can be not trivial, but the exploitation of domino reactions provides an atom- and step-economical method to reach this target. Over the past decades, a lot of efforts have been put on the development of photocatalytic cascades employing both metal-based and purely organic catalysts. Despite the effectiveness of these protocols, catalyst- and additive-free light-induced domino reactions are gaining momentum thank to their efficiency, operational simplicity and sustainability. The increasing number of papers published on this field in the last years is a proof of the appeal of these transformations. In this Review, we discuss domino and multicomponent reactions mediated by light with a focus on photocatalyst- and additive-free processes. The most recent advances in the synthesis of complex nitrogen-, oxygen-, sulphur- and selenium-heterocycles together with multicomponent cascades are analysed with an emphasis on both experimental and mechanistic studies.