N‐Vinyl as N‐H protecting group. Synthesis of cyclic imines from N‐vinyllactams and organolithium reagents

Abstract
On reaction with organolithium reagents followed by hydrolysis and distillation, N‐vinylpyrrolidone (1) gives five‐membered ring imines 3‐8, whereas N‐vinylcaprolactam (2) gives mixtures of seven‐membered ring imines and the corresponding ∈‐amino ketones.