Direct cyclobutylation of 1,6-dihydroazulene gave the spiro hydrocarbon 6, which was subjected to hydride abstraction to lead to the title cation 4. Its hexafluorophosphate salt was isolated as crystals. The cation 4 showed distinctive chemical behavior compared with its three-membered ring homolog. (C) 1998 Elsevier Science Ltd. All rights reserved.