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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
Benzo[cd]azulene skeleton: azulene, heptafulvene, and tropone derivatives
Ingo B Aumüller1, Jari Yli-Kauhaluoma
1Division of Pharmaceutical Chemistry, Faculty of Pharmacy, P.O. Box 56 (Viikinkaari 5 E), FI-00014 University of Helsinki, Finland.
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.
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