Formation of functionalized [3]ferrocenophane derivatives by an enamine condensation reaction

Treatment of 1,1′-diacetylferrocene (10) with excess piperidine and a stoichiometric amount of TiCl4 in pentane leads to CC-coupling of the two functional groups at the ferrocene framework. This enamine condensation reaction leads to the formation of the 1,3-connected dienamine-bridged [3]ferrocenophane system 13a. Complex 13a was characterised by X-ray crystal structure analysis. The analogous TiCl4-mediated coupling and condensation reactions of 10 with morpholine, pyrrolidine or methyl-isopropylamine yield the corresponding substituted [3]ferrocenophane systems 13b–d.