The irradiation of acetylacetone in the presence of oct-1-ene, cyclopentene, cyclohexene, and 1-methylcyclohexene gives substituted heptandiones. These diketones may then be cyclized with acid or base. Irradiation of isopropenyl acetate and acetylacetone gives, after cyclization, m-5-xylenol. The mechanism of the reaction is discussed: it represents the first cycloaddition to an isolated ethylenic linkage.
