Visible-Light-Induced C-H Arylation of Pyrimidines with Arylazo Sulfones.

A catalyst-free visible-light-induced protocol for the C4-selective C-H arylation of pyrimidine derivatives has been developed using arylazo sulfones as aryl radical precursors. Under mild conditions and without external photocatalysts or transition metals, a broad range of arylated pyrimidines were obtained in moderate to excellent yields. Mechanistic studies, including radical trapping experiments and light-control tests, support a visible-light-triggered radical pathway. Selected compounds exhibited promising antiproliferative activities against A549 and MCF-7 cell lines.