Selective synthesis of pseudoionone was achieved by the acetylenic oxy-Cope rearrangement of 4-isopropenyl-3,7-dimethyl-6-octen-1-yn-3-ol () in N-methyl-2-pyrrolidone solvent containing a trace of hydrochloric acid, hydrobromic acid, iodine, ammonium bromide and ammonium chloride catalysts.