Aerobic Oxidative Coupling of 2‑Aminonaphthalenes by Homogenous Nonheme Iron Catalysts

An efficient and general aerobic oxidative coupling method
to prepare
1,1′-binaphthyl-2,2′-diamines (BINAMs) from N-substituted-2-aminonaphthalene (1) based
on [FeIII(cyclen)(Cl)2]Cl catalyst in 1,1,1,3,3,3-hexafluoropropan-2-ol
(HFIP) at room temperature is reported. The highly selective conditions
were applied to prepare a list of N,N′-dialkyl-, N,N′-dibenzyl-,
and N,N′-diaryl-BINAMs with
moderate to high yields. Based on mechanistic studies, which include
control experiments and variable time normalization analysis, it is
suggested that the coupling between [FeIII(cyclen)(1)(OOH)]+2 and 2-aminonaphthalene 1 is the key irreversible step in the catalytic cycle.