Use of a highly effective intramolecular Pauson–Khand cyclisation for the formal total synthesis of (±)-α- and β-cedrene by preparation of cedrone

The cedrene carbon skeleton was directly and efficiently assembled from a simple monocyclic precursor by the strategic use of a high yielding intramolecular Pauson–Khand cyclisation reaction. A small number of further synthetic manipulations provided a concise formal total synthesis of α- and β-cedrene. The cyclisation precursor was readily prepared, with a stereoselective ketone alkenylation selectively providing the olefin required for efficient access to the natural target.