Chemoselective Divergence via Substrate Control: Decarboxylative and Decarbonylative Coupling of 2‐Oxoacids with Allylic Difluorides

Herein, we report the photocatalytic decarboxylative coupling of allylic difluorides and carbon‐centered radicals, which are formed from 2‐oxoacids. This mild and operationally simple protocol enables selective synthesis of monofluoroalkenes via defluorinative CC bond formation. Primary and aryl 2‐oxoacids undergo direct acyl radical addition to allylic difluorides, yielding acylated products exclusively. In contrast, secondary 2‐oxoacids afford mixtures of acylated and alkylated products, while tertiary 2‐oxoacids selectively deliver alkylated products via a decarboxylative/decarbonylation cascade. Thus, the product distribution can be tuned by the substitution pattern of the 2‐oxoacids. The rate of decarbonylation versus radical addition is based on the stability and reactivity of the radical intermediates formed. Computational studies confirm a substrate‐dependent divergence in reaction pathways, with primary 2‐oxoacids undergoing direct acyl radical addition, while secondary and tertiary substrates exhibit competing decarbonylation leading to alkylated products. This study therefore establishes a mechanistic rationale for competitive acylation/alkylation processes starting from 2‐oxoacids.