Retraction of “Access to Cyclobutadienes via an Organocatalytic Dienamine–Iminium–Allenamine Cascade Approach”

A new organocatalytic route to cyclobutadienes from α,β-unsaturated aldehydes and ynals is described. This protocol allows a broad substrate scope and mild conditions. Furthermore, a proposed mechanism of a dienamine–iminium–allenamine cascade process is discussed.