sodium azide), from which 5-acetyltropolone is derived in an 80% yield by ozonolysis or in a 40% yield with sulfuric acid. The considerable differences in the reactivities observed between these 4- and 5-substituted tropolones are discussed. The pKa values of 4- and 5-acetyltropolone and 4- and 5-(3,4,5-trimethoxycinnamoyl)tropolones are also reported.