Photochemical Dual Radical Coupling of Carboxylates with Alkenes/Heteroarenes via Diradical Equivalents

Carboxylate diradical intermediates, with α-carbon and carboxylic oxygen acting as reactive radical centers, represent a highly attractive and long-sought species in reaction design and synthesis. However, capturing these intermediates for diradical coupling reactions poses a formidable challenge due to their inherent instability and spontaneous decarboxylation. Here, we addressed this challenge by temporarily masking the carboxylate oxygen radical reactivity via a photocleavable dynamic oxygen-iodine bond. This approach effectively prevents unwanted decarboxylation and enables the controlled utilization of the carboxylate oxygen radical in forming new bonds. Carboxylates and alkenes/heteroarenes, among the most readily available raw materials, can now seamlessly couple via radical pathways to form γ-butyrolactones, which are common motifs found in numerous natural products and bioactive molecules. Ionic reaction pathways via traditional intermediates of carboxylates are ruled out based on experimental studies and density functional theory (DFT) calculations. This strategy overcomes the substrate limitations of traditional methods, significantly expanding the range of applicable alkenes/heteroarenes. Our method allows transforming carboxylates and alkenes via new reaction modes to diverse products and offers new insights into developing di- and multiradical equivalents for unprecedented reactions and synthetic designs.