ketones are generated in moderate yields (50–60%) from allene or a mono-, di- or tri-substitutedallenic hydrocarbon, n alkyl halide and sodium tetracarbonylferrate. The first step is the formation of a complex anion which results from transfer of the alkyl group on a coordinated CO, then of the acyl ligand thus formed on the allenic sp carbon. Protonation with acetic acid yields a hydroxy-η4-trimethylenemethane