Appropriately functionalized alkenyl oximes cyclize to A'-pyrrolines when treated with trimethylsilyl polyphosphate (PPSE) in refluxing CC4. The reaction is stereospecific, and the reaction conditions do not cause oxime isomerization at a rate comparable to rearrangement cyclization. Terminators found to be compatible with PPSE are trisubstituted olefins and styryl groups; some vinyl chlorides may be used under more forcing conditions (Pz05/CCl, ...