Visible-Light-Induced C-H Silylation of Azauracils with Hydrosilanes

C-H silylation of azauracils was developed via the combination of organic photoredox and hydrogen atom transfer (HAT) catalysis. Using 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as the photocatalyst, quinuclidine as the HAT catalyst, and silanes as the silyl radical source, a variety of silylated azauracils were synthesized in 43-87% yield. Moreover, pyrazinone, cinnolinone, and chromone were also compatible with this catalytic system. The reaction is suitable for late-stage functionalization of drugs and complex molecules, and the transformation can be easily scaled up to gram level. Mechanistic studies suggest that the silylation reaction is likely to proceed through a radical mechanism. image