Depending on the nature of N- and C-substituents, nitrones exhibit diverse reactivity towards electron deficient acetylenes. Observed reactions include formal 1,3-dipolar cycloaddition and nucleophilic addition reactions. Possible involvement of zwitterionic intermediates and an unusual 1-aza-Cope rearrangement account for the generation of unexpected 1 : 1 adducts in the reaction of N-arylnitrones.