New Chiral Ferrocenyl P,S-Ligands for Highly Diastereo-/Enantioselective Catalytic [3 + 2] Cycloaddition of Azomethine Ylides with Cyclic and Acyclic Enones

A new family of chiral ferrocenyl P,S-ligands has been developed and successfully applied in a highly endo-selective catalytic asymmetric cycloaddition of azomethine ylides with various enones, including cyclic and acyclic α-enones. For cyclic α-enones, a [Cu(CH₃CN)₄]ClO₄/(R_c,S_Fc)-2f complex catalyzed the cycloaddition to give the sole endo-cycloadducts in perfect enantioselectivities (normally 99% ee), while an AgOAc/(R_c,S_Fc)-2f catalytic system exhibited good endo/exo selectivities (endo/exo = 91/9 to 96/4) and high enantiocontrol (up to 98% ee) for acyclic α-enones.