Optimization of the External Directing Group Depending on the Substrates for the Regioselective C–H Alkenylation of Phenyl Ethers

Using an external directing group (externalDG), we have succeeded in <i>ortho</i>-selective C-H alkenylation of various DG-free phenyl ethers, including bulky silyl ethers. Also, we demonstrated a strategy to develop regioselective C-H activation by optimizing externalDG depending on the substrate. The means for optimizing externalDG include the selection of the precursor, the addition of a Lewis acid, and changing the ratio of the precursor/Pd, to control the reactivity and regioselectivity.