Isolation of Bicyclopropenylidenes: Derivatives of the Smallest Member Of the Fulvalene Family

摘要

The class of hydrocarbons obtained by formally cross-conjugating two rings through a common exocyclic double bond is known as the fulvalenes, a terminology introduced by Brown. Although the synthesis of compound I (Scheme 1) was reported as early as 1915 by Courtot, the first non-benzannulated fulvalene, a derivative of pentafulvalene II, was prepared in 1954.