Triptycene quinones in synthesis: preparation of triptycene cyclopentenedione and its reactivity as a dienophile.

Triptycenene quinone 1 was converted to triptycene cyclopentenedione 5 through hydroxyquinone-phenyliodonium ylide formation and thermal ring contraction of the latter. Cyclopentenedione 5 reacts as a dienophile and as a dipolarophile with dienes and nitrile oxides, affording polycyclic adducts bearing the triptycene moiety.