Nucleophilic Aromatic Substitution Reactions for the Synthesis of Ferrocenyl Aryl Ethers

A range of ferrocenyl aryl ethers of type Fc–O–Ar (Fc = Fe(η5-C5H5)(η5-C5HnX4–n); n = 2–4; X = H, P(O)(OEt)2, SO2CF3; Ar = 2,4-(NO2)2-C6H3, 4-NO2-C6H4) have been successfully prepared by using the nucleophilic aromatic substitution reaction (SNAr) of Fc–OLi (1a–Li) and electron-deficient aryl fluorides, enabling a new pathway to this rarely described family of organometallic compounds. Initial studies of 1a–Li and o-phosphonato-substituted hydroxyferrocenes (1b–Li) have also been performed, indicating a low nucleophilicity of the oxygen atom. The SNAr reaction protocol tolerates ortho substituents, e.g. phosphonato and sulfonyl groups, resulting in 1,2-X,O (X = S, P) ferrocenyl ethers that can be obtained in a one-pot synthesis procedure including 1,3-O → C anionic phospho- and thia-Fries rearrangements. Within these studies, the first 1,3-diortho-functionalized ferrocenyl aryl ether could be synthesized. An electrochemical study of the redox potentials of the obtained compounds allows conclusions on the ...