Controllable Radical Reactions of 1,3-Dienes with Light

The direct conversion of feedstock chemicals into value-added products is a popular theme in synthetic chemistry. Since 1,3-dienes are some of the most ubiquitous and readily synthesizable starting materials, there is great interest in developing synthetic methods for their functionalization. However, due to the existence of multiple reactive sites on the 1,3-diene, achieving high regio- and enantioselectivity remains elusive. Traditional synthetic processes for 1,3-diene transformations often face challenges, such as low selectivity, high energy consumption, and the generation of undesirable byproducts. Driven by advances in synthetic technologies, synthesis methods utilizing radicals have emerged as a powerful platform for creating valuable chemical motifs. Photocatalytic approaches harness light energy to facilitate radical reactions under mild conditions, offering enhanced control over the reaction pathways and improved selectivity. In this review, we provide an insightful mechanistic overview of these radical-based photocatalytic innovations used in the controllable divergent radical reactions of 1,3-dienes. The reactions are categorized into 1,2- and 1,4-hydrofunctionalization and 1,2- and 1,4-difunctionalization. Perspectives on the future development of this emerging field are also given.