Synthesis of the 8-cycloheptatrienylheptafulvenyl cation

Abstract

The chlorocarbenoid reagent prepared from methylene dichloride and sodium bistrimethylsilylamide adds, at least in part, to the central double bond of heptafulvalene, and the intermediate chlorocyclopropane ionises to give the title cation (3a). Chloro(phenyl)carbene and dichlorocarbene behave similarly to give the 8-phenyl and 8-chloro cations. The title cation is one of the most stable hydrocarbon cations yet prepared.