Syntheses of (±)‐ and Enantiomerically Pure (+)‐Longifolene and of (±)‐ and Enantiomerically Pure (+)‐Sativene by an Intramolecular de Mayo Reaction

Starting from 2‐cyclopentenoyl chloride ((RS)‐ or (S)‐8), the racemic as well as the enantiomerically pure (+)‐sesquiterpenes longifolene ((±)‐ and (+)‐1, resp.) and sativene ((±)‐ and (+)‐2, resp.) were synthesized efficiently by a sequence of nine and ten steps, respectively. The key sequence 10 → 16 → 3 is the first strategic application of an intramolecular photoaddition/retro‐aldolization sequence (intramolecular de Mayo reaction) in organic synthesis.