The More Gold—The More Enantioselective: Cyclohydroaminations of γ‐Allenyl Sulfonamides with Mono‐, Bis‐, and Trisphospholane Gold(I) Catalysts

A series of chiral mono‐, di‐, and trinuclear gold(I) complexes have been prepared and used as precatalysts in the asymmetric cyclohydroamination of N‐protected γ‐allenyl sulfonamides. The stereodirecting ligands were mono‐, di‐, and tridentate 2,5‐diphenylphospholanes, which possessed C₁, C₂, and C₃ symmetry, respectively, thereby rendering the catalytic sites in the di‐ and trinuclear complexes symmetry equivalent. The C₃‐symmetric trinuclear complex displayed the highest activity and enantioselectivity (up to 95 % ee), whilst its mono‐ and dinuclear counterparts exhibited considerably lower enantioselectivities and activities. A similar trend was observed in a series of mono‐, di‐, and trinuclear 2,5‐dimethylphospholane gold(I) complexes. Aurophilic interactions were established from the solid‐state structures of the trinuclear gold(I) complexes, thereby raising the question as to whether these secondary forces were responsible for the different catalytic behavior observed.