Monodentate Transient Directing Group Enabled Pd-Catalyzed Ortho-C-H Methoxylation and Chlorination of Benzaldehydes.

We report Pd-catalyzed ortho-C-H methoxylation and chlorination of benzaldehydes by employing monodentate transient directing groups (TDGs) as an alternative strategy to bidentate TDGs. More importantly, a single crystal of benzaldehyde imine ortho-cyclopalladium intermediate was successfully obtained, and its structure was unambiguously determined by X-ray diffraction, which clearly showed that it was a binuclear palladium species bridged by a pyridone ligand. The utility of this approach was further demonstrated through the synthesis of key intermediates of natural products and drugs.