Acid catalysis of the retro-diels alder reaction. Formation and electrophilic reactivity of 2-methylene-1,3-cyclopentanedione.

The acid mediated decomposition of the Diels-A1der adduct of 1,3-cyclopentanedione with anthracene was studied. An extremely facile, acid catalyzed retro-Diels-Alder fragmentation produces 2-methylene-1,3-cyclopentanedione, which undergoes twofold electrophilic substitution on the cognate anthracene nucleus.