β C-H di-halogenation via iterative hydrogen atom transfer

A radical relay strategy for mono-and di-halogenation (iodination, bromination, and chlorination) of sp3 C-H bonds has been developed. This first example of b C-H di-halogenation is achieved through sequential C-H abstraction by iterative, hydrogen atom transfer (HAT). A double C-H functionalization is enabled by in situ generated imidate radicals, which facilitate selective Nc to Cc radical translocation and tunable C-X termination. The versatile, geminal di-iodide products are further elaborated to b ketones and vinyl iodides. Mechanistic experiments explain the unique di-functionalization selectivity of this iterative HAT pathway, wherein the second C-H iodination is twice as fast as the first.