Formal Homoiodo Allylsilane Annulations: Dual Total Syntheses of (±)-Hirsutene and (±)-Capnellene

Dual
total syntheses of (±)-hirsutene and (±)-capnellene,
two typical linear triquinane sesquiterpenes, were achieved via a
formal [3 + 2] annulation strategy, as illustrated schematically.
Cyclic homoiodo allylsilanes were employed as key bifunctional synthons
in the synthesis, which were readily prepared from the corresponding
cyclopropanated cyclopentenones. A formal [3 + 3] annulation approach
for the elaboration of the bicyclic framework of the Eudesmane sesquiterpenoids
based on this type of synthon was also developed.