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.