Unusual carbamate-directed CH-activation at an annulated ferrocenophane framework

The tetrahydroazepine-annulated [3] ferrocenophane carbamate (4) was synthesized by two different linear routes starting from the readily available alpha-dimethylamino[3] ferrocenophane-ortho-carbaldehyde rac-6. The carbamate directed lithiation of 4 resulted in a selective attack at a (Cp)C-H bond at the higher substituted lower [3] ferrocenophane Cp-ring to eventually yield the respective ester (18) after treatment with ClCO2Me.