η4 to η5: Stereocontrolled reactivation of exocyclic triene iron complexes

Abstract The protonation of prochiral exocyclic double bonds in cyclohexa-2,4-dieneiron(0) complexes introduces a chiral centre adjacent to the emergent η 5 -cyclohexadienyliron(1+) portion of the product. This reaction has been shown to be fully diastereoselective. The stereochemical course of the reaction has been elucidated by X-ray crystallography and correlated with a complementary procedure starting from dienol complexes.