Twofold unsymmetrical C-Si bond bifunctionalization of 2,6-di(trimethylsilyl) benzyl alcohols has been achieved in one pot via sequential [1,4]-Csp2 to O-silyl migration. The hydroxyl group functions as an "on-off-on" switch to control two successive silyl migrations, and 4,7-dimethyl-o-phenanthroline ligand favors cleavage of the endocyclic C-Si bond. Diverse Csp3/Csp3 or Csp2/Csp3 electrophiles can be installed at the 2- and 6-positions. This approach was used to chemoselectively functionalize the three C-Si bonds of 2,4,6-tri(trimethylsilyl) benzyl alcohol, transforming it into isochroman derivatives. The approach even works as a five-component reaction to construct complex symmetric structures.