Scheme 1. Stoichiometric Observation of Relevant Reaction Intermediates by 31P NMR Spectroscopy.

Quantities shown in blue are chemical shifts of the phosphorus atoms in major species shown; see Supporting Information for details. (a) (MeO)2MeSiH, benzene; (b) cyclohexylallene, benzene; (c) acetophenone, benzene; (d) (MeO)2MeSiH.