Diphenylcyclopropenone, condensation with 3-methylindole

In addition, diphenylcyclopropenone condensed with 3-methylindole in the 2-position to yield 36 and with 2-phenyl-7-methylindolizine to yield 37. Similarly, cycloheptenocyclopropenone reacted with 2-phenylindole, leading to 38. Attempts to generate the free bases by treatment of the salts with a variety of bases of low nucleophilicity produced, at best, only fleeting colors attributable to the deprotonated species. The authors suggest that an ionic polymerization takes place due to the dipolar character of the free azapentatriafulvalenes. This hypothesis has been supported by the observation that the azafulvalenium salts were regenerated from the polymeric material by protonation in strongly acidic solution (Scheme 11). 

---