Ketyl radical reactivity via atom transfer catalysis

Iodine smooths the way to ketyl radicals Chemists typically transform carbonyl compounds through polar two-electron reactions. It is also possible to pursue radical coupling strategies by adding just one electron to form a ketyl group. However, the strong reductant supplying that electron often limits the reaction's versatility. Wang et al. report a mild means of forming ketyls by first adding acetyl iodides across the C=O bond (see the Perspective by Blackburn and Roizen). A photoactivated manganese catalyst then temporarily pulls the iodine away, leaving a ketyl to couple with alkynes. The iodine then returns to one of the alkyne's carbons, stabilizing the product but remaining poised for further transformations. Science , this issue p. 225 ; see also p. 157