Diastereoselective Domino Synthesis of Triquinanes

Significance

An intramolecular Diels-Alder ­(IMDA)-tandem metathesis strategy is used to access a vinyl triquinane skeleton and a formal synthesis of (±)-Δ^9(¹²)-capnellene is realized. A variety of strategies have been applied to the synthesis of similar terpenoids (see Review below) and this sequence is an interesting addition. The authors also present a discussion of two possible metathesis sequences: ring-opening-ring-closing metathesis (ROM-RCM) versus ring-closing-ring-opening-cross-metathesis (RCM-ROM-CM, pictured). Evidence supporting the latter proposal is disclosed.

Review: G. A. Mehta, A. Srikrishna Chem. Rev. 1997, 97, 671-719.