Synthesis of Ferrocenyl Alkyne–Cu(I) π‑Complexesvia Copper-Promoted 8‑Aminoquinoline-Directed C–H BondAlkynylations

A highly monoselective synthesis of ferrocenyl alkynes was achieved via Cu-promoted ferrocene C(sp2)–H bond activations. The reaction employs an 8-aminoquinoline group as the directing group and terminal alkynes as the alkyne source. It was found the alkynylation products actually complex with the in situ generated Cu(I) ions to give robust and stable alkyne π-copper complexes. In addition, these alkyne π-copper complexes could be freed of the copper ions to give various ferrocenyl alkynes in almost quantitative yields. The test results also showed that the alkyne π-copper complexes could be reformed from the free alkynes upon treating them with Cu(I) salts.