Preparation of Tetraphenylazulenequinodimethanes from the Reactions of Azulenequinones with Diphenylketene and the 1H NMR and UV-vis Spectral Studies in Acidic Media

3-Bromo-1,5-azulenequinone and 3-bromo-1,7-azulenequinone reacted with diphenylketene to give the corresponding tetraphenylazulenequinodimethane, which has both diphenylfulvene and diphenylheptafulvene structures. The protonation occurred at the diphenylmethylene group on the seven-membered ring to form a cycloheptatrienylium ion.