Reaction of 1,1′‐Divinyl Ferrocene with One‐Electron Oxidants: Entry into Functionalised [4]Ferrocenophanes and Observation of an Isotope‐Dependent Chemoselectivity Effect

1,1′‐Divinyl ferrocene ( 2 ) reacts with K 3 [Fe(CN) 6 ] under basic biphasic conditions to give a [4]ferrocenophane ( 4 ) in good yield. Incorporating deuterium labels into the internal positions of the vinyl groups of 2 affects the chemoselectivity of the reaction; thus under identical reaction conditions, [D 2 ]‐ 2 reacts to provide a diol‐functionalised [4]ferrocenophane, [D 2 ]‐ D / L ‐ 6 in addition to the expected keto‐alcohol, [D 1 ]‐ 4 . Variants on this one‐electron oxidative cyclisation methodology can be used to give other [4]ferrocenophanes; thus, the reaction of 2 with CuCl 2 in MeOH or i PrOH leads to dialkoxy [4]ferrocenophanes 19 and 20 , respectively, whereas the reaction of 2 with benzyl carbamate in the presence of t BuOCl gives a bis(carbamate)[4]ferrocenophane, 21 . Mechanisms to account for the formation of the products, the stereoselectivity, and the unusual isotope‐dependent chemoselectivity in the reaction of 2 and [D 2 ]‐ 2 with K 3 [Fe(CN) 6 ] are proposed.