Site‐Selective CH Alkylation of Pyrimidin‐2(1 H )‐Ones Enabled by Visible‐Light‐Induced Organophotocatalysis

A visible‐light‐induced photocatalytic method for regioselective CH alkylation at the electrophilic C4 and C6 positions of N1‐substituted pyrimidin‐2(1 H )‐ones using alkyl trifluoroborates, an acridinium‐based photocatalyst, and potassium persulfate as oxidant is reported. The developed general protocol enables direct stepwise introduction of uncommon secondary and tertiary alkyl groups via a radical oxidative addition pathway, thereby expanding the accessible chemical space of substituted pyrimidines in a principally new direction. The impact of the nature of substituents at positions N1 and C5, as well as the effect of the acid additive, was investigated, providing a practical strategy for the synthesis of highly decorated heterocycles. The elaborated methodology predicted high suitability for both parallel synthesis and multigram‐scale production of the target pyrimidones.