A dual reactivity of 2‐azetidinone‐tethered allenols may occur by judicious choice of the electrophilicreagents, namely halogenating versus selenating reagents. Using common substrates, structurally different compounds, namely tetramic acids (from N‐bromosuccinimide) or spirocyclic seleno‐β‐lactams (from N‐phenylselenophthalimide), can be readily synthesized by these divergent protocols.