Synthesis of disubstituted furans catalysed by [(AuCl)₂(μ-bis(phosphino)metallocene)] and Na[BArF₂₄]

The catalytic activity of a series of [(AuCl)₂(μ-PP)] (PP = 1,1'-bis(phosphino)metallocene ligands) compounds in the presence of Na[BArF₂₄] (BArF₂₄ = tetrakis(3,5-bis(trifluoromethyl)phenyl borate)) was examined in the formation of disubstituted furans from pyridine-N-oxide and terminal alkynes. The products of these reactions were typically the 2,5-disubstituted furans, but in the case of using 2-ethynylpyridene, the 2,4-disubstituted furan formed. The catalytic efficiency was dependent upon both the nature of the terminal alkyne and the 1,1'-bis(phosphino)metallocene ligands. During the course of this study, two new compounds, [(AuCl)₂(μ-dppr)] and [(AuCl)₂(μ-dppo)] (dppr = 1,1'-bis(diphenylphosphino)ruthenocene; dppo = 1,1'-bis(diphenylphosphino)osmocene), were prepared and characterized by NMR. X-ray crystal structures of both compounds were determined and the oxidative electrochemistry of these new compounds was examined.