Mechanistic Insights into the Base-Mediated Deuteration of Pyridyl Phosphonium and Ammonium Salts

Pyridines can be deuterated at remote sites by treatment with KOtBu in DMSO-d6, although without discrimination between the meta- and para-position. Herein, base-catalyzed deuterations have been studied, computationally and experimentally, on a series of pyridyl phosphonium and ammonium salts having a temporary electron-withdrawing group to block the para-position while increasing the acidity in the other positions.