Ring-Expansion of Tertiary Cyclic α-Vinylamines by Tandem Conjugate Addition to (p-Toluenesulfonyl)ethyne and Formal 3-Aza-Cope Rearrangement.

A novel ring-expansion protocol is based on the conjugate additions of cyclic α-vinylamines to (p-toluenesulfonyl)ethyne, followed by aza-Cope rearrangements of the resulting zwitterions, to afford medium and large-ring cyclic amines under remarkably mild conditions.