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.