Cyclopentadienyliron-mediated introduction of functionalized alkyl or alkynyl groups to arenes in an addition-demetallation sequence

Article abstract of DOI:10.1016/0022-328X(91)80248-I

Nitromethyl, cyanomethyl, and phenylethynyl anions add selectively ortho to arenes containing electron-withdrawing groups and complexed with cyclopentadienyliron.Under similar reaction conditions anions such as alkyl, dichloromethyl and trichloromethyl add in a non-selective way.Addition of the trichloromethyl anion is thermodynamically controlled at extended reaction times and, due to the size of the anion, the meta addition is favoured.Demetallation of adducts leads to ortho-nitromethylated, cyanomethylated or phenylethynylated arenes, respectively.With symmetrical arene complexes the addition-demetallation sequence leads to the introduction of a trichloromethyl group into the arene ring, yielding a single product.A one-pot procedure for trichloromethylation of dialkylarenes starting from appropriate cyclopentadienyliron complexes gives β-trichloromethylated dialkylarenes in a good yield.