Asymmetric synthesis of a (2Z,7E)-cyclononadiene by an intramolecular cycloalkylation and insight to its conformational properties

Here, we report a novel synthesis of a monosubstituted, enantio- and diastereomerically enriched trans-cyclononadienol. The reaction consists of an enantioselective (-)-sparteine-mediated allylic lithiation of an achiral 7-chlorononadienyl carbamate and a subsequent stereospecific intramolecular allyllithium-allyl chloride coupling. The stereochemical course of the cyclization has been determined, and the high configurative stability of the chiral nine-membered carbocycle has been investigated by kinetic measurements and rationalized by computational calculations.