Abstract: Substitutions with cuprous acetylides provide a most convenient route to a wide variety of acetylenes and heterocyclic arrays. This summarizing work casts these reactions into a general pattern for copper (1) substitution. The reactivity of acetylides toward bond type, the kinetics of aromatic substitution, the geometry of allylic substitution, the nature and path of the heterocyclic synthesis, and some mechanistically instructive ring size ...