Site-selective bromination of sp C-H bonds.

A method for converting sp C-H to C-Br bonds using an -methyl sulfamate directing group is described. The reaction employs Rh(oct) and a mixture of NaBr and NaOCl and is performed in aqueous solution open to air. For all sulfamates examined, oxidation occurs with high selectivity at the γ-carbon, affording a uniquely predictable method for C-H bond halogenation. Results from a series of mechanistic experiments suggest that substrate oxidation likely proceeds by a radical chain process. Initial formation of an -halogenated sulfamate followed by Rh-mediated homolysis generates an N-centered radical, which serves as the active oxidant.