Catalytic Functionalization of Unactivated sp3 C-H Bonds via exo-Directing Groups: Synthesis of Chemically Differentiated 1,2-Diols

We describe a Pd-catalyzed site-selective functionalization of unactivated aliphatic C-H bonds, providing chemically differentiated 1,2-diols from mono-alcohol derivatives. The oxime was employed as both a directing group (DG) and an alcohol surrogate for this transformation. As demonstrated in a range of substrates, the C-H bonds beta to the oxime group are selectively oxidized. Besides activation of the methyl groups, methylene groups (CH2) in cyclic substrates and methine groups (CH) at bridge-head positions can also be functionalized. In addition, an intriguing oxidative skeleton rearrangement was observed using the menthol-derived substrate. The use of exo-directing groups in C H activation, as illustrated in this work, would potentially open doors for the discovery of new transformations and new cleavable DGs.