Binap-Gold(I) versus Binap-Silver Trifluoroacetate Complexes as Catalysts in 1,3-Dipolar Cycloadditions of Azomethine Ylides

The 1,3‐dipolar cycloaddition between azomethine ylides and alkenes is efficiently catalysed by [{(Sa)‐Binap‐Au(tfa)}2] (Binap=2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl; tfa=trifluoroacetyl). Maleimides, 1,2‐bis(phenylsulfonyl)ethylene, chalcone and nitrostyrene were suitable dipolarophiles even when using sterically hindered 1,3‐dipole precursors. The results obtained in these transformations improve the analogous ones obtained in the same reactions catalysed by [Binap–Ag(tfa)]. In addition, computational studies have also been carried out to demonstrate both the high enantioselectivity exhibited by the chiral gold(I) complex, and the non‐linear effect observed in this transformation. Natural (enantio)selection: The enantioselective 1,3‐dipolar cycloaddition of azomethine ylides and electrophilic alkenes has been successfully catalysed by a [{(Sa)‐Binap–Au(tfa)}2] (Binap=2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl; tfa=trifluoroacetyl) complex (see scheme; EWG=electron‐withdrawing group). The origin of the enantioselectivity as well as the observed non‐linear effect were analysed with computational tools.