Ynolate Chemistry. Reaction of a Silylynolate with Aziridines Leading to γ-Lactams

A silylynolate, generated via the carbonylation of lithium silyldiazomethane, was reacted with N-tosyl aziridines to produce various five-membered lactams in good yields. The key step of this reaction involves the ring-opening ketenylation of aziridines by the silylynolate. The reaction proceeded in a highly stereoselective manner, and ketenylation took place at the less hindered carbon. When treated with aldehydes prior to protonation, the alpha-silylated lactam enolates gave alpha-vinylidene gamma-lactams. These reactions represent a unique path to the generation of and for controlling the reactivity of a rare class of reactive intermediates, namely, acyllithium derivatives and ynolates.