Reactivity of [m]ferrocenophanones: The aldol condensation

Abstract

Investigation of the reaction of [m]ferrocenophanones with p-chlorobenzaldehyde in basic medium showed that these cyclic ketones are much more reactive than their acyclic counterparts. The size of the bridge and the position of the carbonyl group influenced the reaction. Thus, [m]ferrocenophan-1-ones (m =3,4 afforded β-hydroxyketones only, [5]ferrocenophan-1-one gave in addition an α,β-unsaturated ketone, and [4]ferrocenophane-2-one yielded only α,β-unsaturated ketones. Oxidation of [m]ferrocenophanes with MnO2 furnished the expected monoketones and [4]ferrocenophane-1,4-dione and [5[ferrocenophane-1,2-dione. The preparation of [5]ferrocenophane-1,5-dione was also improved.