Direct benzylic metalation of a phenethylamine derivative: potassium as the key to both generation and stabilization of a labile anion.

t-BuLi-t-BuOK selectively metalates the benzylic position of 2-phenylethyldimethylamine under mild conditions without occurrence of β-elimination in the resulting metalated species. Theoretical and structural studies indicate that potassium is crucial for both the lowering of the barrier of the initial deprotonation step and the stabilization of the labile anion.