Formation of Medium-Sized Nitrogen Heterocycles from γ-Silyloxy-γ-Lactams

Nitrogen heterocycles can be prepared by performing ring-expansion reactions of γ-silyloxy-γ-lactams, which are available by the annulation reactions of allylic silanes. Nucleophilic substitution of the annulation products and subsequent translactamization of nitrogen-tethered γ-lactams provide six-, seven-, and eight-membered ring lactams. An enantiomerically enriched δ-lactam formed from this method was elaborated to form the hydroxypiperidine core structure of the pseudodistomin alkaloids.