We have demonstrated a novel oxidative generation of ammonium ylides by employing allylic amines having a silyl group. Treatment of N-(alpha-silylmethyl)-N-allylic amines with an oxidant, followed by acetic anhydride, brought about a tandem Brook rearrangement/silicon Polonovski reaction via the generation of ammonium ylides to give the corresponding amides, whereas the reaction of N-(alpha-cyano-alpha-silylmethyl)-N-allylic amines with an oxidant afforded the corresponding formamides.