Palladium(II)-Catalyzed Selective Arylation of Tertiary C-H Bonds of Cyclobutylmethyl Ketones Using Transient Directing Groups.

We report the first example of selective Pd -catalyzed tertiary C-H activation of cyclobutylmethyl ketones using a transient directing group. An electron-deficient 2-pyridone ligand was identified as the optimal external ligand to enable tertiary C-H activation. A variety of cyclobutylmethyl ketones bearing quaternary carbon centers was readily accessed without preinstalling internal directing groups in up to 81 % yield and >95 : 5 regioisomeric ratios of tertiary C-H arylation to β-methylene (β-methyl) or γ-C-H arylation.