Thermal activation of the normal Claisen products, the enones 4, 7 and 14 in the presence of a catalytic amount of propionic acid generated the isomeric enones 6, 9 and 15 via the sequential intramolecular ene-reaction of the enol tautomer followed by 1,5-hydrogen transfer (or retro ene-reaction) of the resultant acetyl cyclopropane intermediate. Conversion of the enones 9 and 15 into the corresponding