1,2-Diketones as in situ persistent radical precursors: symmetric and unsymmetric diacylation of alkenes under visible light.

Radicals are key reactive intermediates in organic synthesis; however, their high reactivity often undermines selectivity in conventional systems. The persistent radical effect (PRE) has emerged as a powerful strategy to mitigate this limitation by enabling sustained, selective radical transformations. Herein, we report a catalyst-free, visible-light-enabled alkene diacylation in which 1,2-diketones serve as in situ precursors to persistent α-ketyl radicals, enabling access to both symmetric and unsymmetric 1,4-diketones. For symmetric products, 1,2-diketone generates the persistent α-ketyl radical, while photoinduced homolysis of a second diketone provides a transient acyl radical; regioselective addition affords an α-hydroxyketone that undergoes Norrish type I fragmentation with aldehyde extrusion. For unsymmetric products, SET redox exchange between 1,2-diketones and α-keto acids generates the persistent radical and an acyl radical, and sequential radical addition gives unsymmetric 1,4-diketones. This strategy obviates the need for transition-metal or N-heterocyclic carbene (NHC) catalysis and enables direct access to persistent α-ketyl radicals under mild, catalyst-free photochemical conditions. Collectively, these results expand the transformation chemistry of 1,2-diketones and establish them as readily available, inexpensive persistent acyl radical equivalents for selective radical synthesis.