12 aa, R'= Ph, Ra= CH,, b, R1= Ph; Ra= C, H,; c, R1= yellow dimers revert to the deep purple compounds. It is assumed that the purple materials observed are the desired pyrrolone oxides 10, since both the triphenyl derivative 3 and tetraphenylcyclopentadienone also have deep purple colors. It is evident that replacement of any of the aryl substituents of 3 results in a significant destabilization of this heterocyclic system.
