Sequential Friedel-Crafts diacetylation of ferrocene: Interannular proton transfers as a mechanistic probe

Article abstract of DOI:10.1021/om00018a047

(Pentadeuteriocyclopentadienyl)cyclopentadienyliron(II), 4, was prepared by the sequential addition of lithium tris(trimethylsilyl)cyclopentadienide and lithium pentadeuteriocyclopentadienide to FeBr₂ followed by fluoride-induced removal of the trimethylsilyl groups of the resulting ferrocene 3. Analysis of the deuterium content of the acetylferrocene 5 and the 1,1′-diacetylferrocene 7, obtained from the Friedel-Crafts acetylation of 4, reveals that the former is formed by initial exo attack of AlCl₃-CH₃COCl, whereas precomplexation of the electrophile at the metal center (endo attack) precedes the formation of the latter.