Benzo[<i>cd</i>]azulene Skeleton: Azulene, Heptafulvene, and Tropone Derivatives

Abstract

Due to our interest in protein kinase modulating compounds, we developed syntheses for benzo[cd]azulenes. By using very common catalysts and reagents, such as t-BuOK, HCl, and mCPBA, the commercially available guaiazulene is converted in three steps into tricyclic tropone derivatives. Electrophilic aromatic substitution reactions of guaiazulene proceed without a catalyst. Complex one-pot reactions convert 1'-hydroxyalkyl azulenes into tricyclic heptafulvenes, and finally, the mild oxidant mCPBA cleaves the semicyclic C horizontal lineC double bonds to furnish tropones.