N-Heterocyclic Carbene (NHC) Binuclear Gold Complexes Catalyzed Aminoarylation of Olefins

N-Heterocyclic carbene (NHC) binuclear gold complexes and mononuclear gold complex have been successfully prepared from 1,1'-binaphthalenyl-2,2'-diamine (BINAM) in good yields. Their structures have been unambiguously determined by spectroscopic data and X-ray diffraction. On the basis of X-ray diffraction, a weak interaction between Au-Au has been identified in the N-heterocyclic carbene (NHC) binuclear gold complex 4b, in which the distance of Au(1)-Au(1) is 4.190 angstrom. We also found that NHC-binuclear gold complex 4b is a more effective catalyst than that of NHC-mononuclear gold complex in the aminoarylation of olefins under identical conditions. Based on these experimental data, the improved yield of aminoarylation is possibly attributed to the weak Au(I)-Au(I) interaction in the N-heterocyclic carbene (NHC) binuclear gold complex 4b. A plausible reaction mechanism has been proposed on the basis of previous literature. The reaction procedure is quite simple. When NHC-gold(I) catalyst 4b (3 mol%, 3.0 mu mol) was dissolved in solvent (2.0 mL) in a flame-dried Schlenk tube equipped with a septum cap and stirring bar, the additive AgSbF6 (6.0 mu mol) was added under argon, and then the mixture was stirred under argon at room temperature for 10 min. Alkylamine (0.1 mmol), arylboronic acid (0.2 mmol), and selectfluor (0.2 mmol) were added, and then the reaction mixture was stirred at 60 degrees C for 12 h. The crude product was concentrated under reduced pressure, and purified by flash chromatography on silica gel (eluent: EtOAc/petroleum ether = 1/16) to yield the pure corresponding product. Recently, a number of bis(gold) vinyl species have been isolated from homogeneous gold catalysis and have been identified as the key intermediate in the catalytic process. Meanwhile, binuclear gold complexes have been also realized as the key species in the homogeneous gold catalysis recently. In this paper, we first disclosed that the N-heterocyclic carbene (NHC) binuclear gold complex has a weak interaction between Au(I)-Au(I), which plays an important role in the aminoarylation of olefins.