Visible‐Light‐Driven 1,4‐Hydroalkylation of 1,3‐Conjugated Dienes with 1,3‐Dicarbonyls ^†

Comprehensive Summary The selective radical hydroalkylation of 1,3‐dienes, particularly using readily available alkyl radical sources, remains a challenging synthetic transformation, primarily due to the high reactivity of radical intermediates and the presence of multiple reactive sites within the 1,3‐diene framework. Herein, we disclose a mild and efficient visible‐light‐driven 1,4‐hydroalkylation of conjugated dienes with perfect atom economy. The key steps of this protocol involve catalytic generation of C ‐radicals from readily available 1,3‐dicarbonyls, followed by a radical 1,4‐addition to form the benzyl radicals, which then undergo a single‐electron‐reduction and final protonation. This method features broad substrate scope, operational simplicity and high efficiency. A variety of readily available malonates, β ‐ketoesters and diversely substituted ary‐1,3‐dienes were well accommodated, yielding the corresponding 1,4‐hydroalkylated products in generally good yields (50%–82% yields). This approach also broadens the synthetic utility of 1,3‐dicarbonyl compounds, facilitating gram‐scale synthesis, late‐stage modifications of drug‐like molecules and further synthetic transformations. As a result, numerous high value‐added molecules were obtained, showcasing the synthetic potential of this method. Control experiments revealed that visible‐light‐irradiation, the photocatalyst and the base are all indispensable for the success of this protocol. Preliminary mechanistic studies, encompassing radical‐trapping experiment, deuteroxide quenching experiment, light on‐off experiments and Stern‐Volmer experiments, support the proposed mechanism.