Linear halogenated N, N-disubstituted amides afford cyclic amides in good yields by reaction with'activated'lithium dialkylamides. However, the same reaction with substituted amides gives mainly ω-ethylenic amides. In the same way, N-substituted γ-and δ-lactams with an ω-halogenated chain in the α position afford pure spirolactams whereas the reaction of ϵ-Iactams furnishes a mixture of spiro and ethylenic compounds.
