McKenna Reaction—Which Oxygen Attacks Bromotrimethylsilane?

The first experimental proof of the course of silylation in the McKenna reaction, one of the most widely used reactions for the synthesis of organophosphorus acids, is presented. The reaction (in acetonitrile) proceeds via an attack of the terminal oxygen from the dialkyl phosphonate on the silicon atom in bromotrimethylsilane. Isotopically enriched diethyl phenylphosphonates (P═17O or P═18O) were used as the model compounds. The location of the isotopic tracers was detected using 31P and 17O NMR spectroscopy.