6533b827fe1ef96bd12865ea

RESEARCH PRODUCT

Gold(I) Complexes Nuclearity in Constrained Ferrocenyl Diphosphines: Dramatic Effect in Gold‐Catalyzed Enyne Cycloisomerization

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International audience; Di-tert-butylated-bis(phosphino)ferrocene ligands bearing phosphino substituents R (R=phenyl, cyclohexyl, isopropyl, mesityl, or furyl) allow tuning the selective formation of Au(I) halide complexes. Thus, dinuclear linear twocoordinate, but also rare mononuclear trigonal three-coordinate and tetrahedral four-coordinate complexes were formed upon tuning of the conditions. Both Au(I) chloride and rarer Au(I) iodide complexes were synthesized, and their X-ray diffraction analysis are reported. The significance of the control of structure and nuclearity in Au(I) complexes is further illustrated herein by its strong effect on the efficiency and selectivity of gold-catalysed cycloisomerization. Cationic linear digold(I) bis(dicyclohexylphosphino) ferrocenes outperform other catalysts in the demanding regioselective cycloisomerization of enyne sulphonamides into cyclohexadienes. Conversely, tetrahedral and trigonal cationic monogold(I) complexes were found incompetent for enyne cycloaddition. We used the two-coordinate linear electron-rich Au(I) complex 2b (R=Cy) to extend the scope of selective intramolecular cycloaddition of different 1,6-enyne sulfonylamines with high activity and excellent selectivity to the endo cyclohexadiene products.