Ruthenium(II)-catalyzed C-H acyloxylation of phenols with removable auxiliary.

Intermolecular C-H acyloxylations of phenols with removable directing groups were accomplished with a versatile ruthenium catalyst. Specifically, a cationic ruthenium(II) complex, formed in situ, enabled the chemoselective C-H oxygenations of a broad range of substrates. The catalyst proved tolerant of synthetically valuable functional groups, and the substrate scope included both (hetero)aromatic and, the more challenging, aliphatic carboxylic acids. The proposed reaction mechanism involves a reversible C-H ruthenation and an oxidatively induced C-O-bond-forming reductive elimination.