Distal Ruthenaelectro‐Catalyzed <i>meta</i> ‐C−H Bromination with Aqueous HBr
Yulei Wang, Hendrik Simon, Xinran Chen, Zhipeng Lin, Shan Chen, Lutz Ackermann
Abstract
Abstract While electrochemical ortho ‐selective C−H activations are well established, distal C−H activations continue to be underdeveloped. In contrast, we herein describe the electrochemical meta ‐C−H functionalization. The remote C−H bromination was accomplished in an undivided cell by RuCl 3 ⋅3 H 2 O with aqueous HBr. The electrohalogenation proceeded under exogenous ligand‐ and electrolyte‐free conditions. Notably, pyrazolylarenes were meta ‐selectively brominated at the benzenoid moiety, rather than on the electron‐rich pyrazole ring for the first time. Mechanistic studies were suggestive of an initial ruthenacycle formation, and a subsequent ligand‐to‐ligand hydrogen transfer (LLHT) process to liberate the brominated product.