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 iPrOH leads to dialkoxy [4]ferrocenophanes 19 and 20, respectively, whereas the reaction of 2 with benzyl carbamate in the presence of tBuOCl 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.