Syntheses, crystal structures, and electrochemical properties of multi-ferrocenyl resorcinarenes

Tetraaryl and tetraferrocenyl resorcinarenes 1a–1c have been synthesized by the HCl-catalyzed condensation of resorcinol with aromatic aldehydes or ferrocenecarbaldehyde, which were fully alkylated with ethyl α-chloroacetate to give the activated ethyl resorcinarylacetates 2a–2c. Reaction of 2a–2c with hydrated hydrazine yielded the resorcinarene acylhydrazine derivatives 3a–3c, from which the multi-ferrocenyl functional groups were selectively and efficiently introduced on the upper rim, or on the lower rim, or both on the upper and lower rims of resorcinarenes 4a–4c and calixarenes 4d–4f based upon the condensation reactions of acylhydrazones with ferrocenecarboxaldehyde.