Ring-opening reactions of aromatic N-heterocycles by scandium and yttrium alkyl complexes

The C-N bond in aromatic N-heterocycles is a strong bond, its cleaving involving mostly examples of metal-element multiple bonds. We report on the C-C coupling of two molecules of an aromatic N-heterocycle mediated by scandium and yttrium benzyl complexes supported by a ferrocene 1,1'-diamide ligand. The reaction with 1-methylimidazole leads, ultimately, to the formation of a ring-opened imidazole couple to a 1-methylimidazole fragment, a structure showing extended conjugation of double bonds. The experimental evidence agrees with involvement of only sigma bonds in these transformations.