Synthesis of α-methylene propellanone via the strategic employment of metal-mediated cyclisation chemistry

Biologically active α-methylenene propellanone has been synthesised in 12 steps in an overall yield of 11%. The key step of the synthesis, an intramolecular Pauson–Khand reaction, proceeds in good yield under alkyl sulfide promotion conditions, to furnish the 5,5-fused moiety within the target. Samarium diiodide-induced intramolecular conjugate addition onto the resulting cyclopentenone was used to complete the intriguing [3.3.3] propellanone skeleton.