TADDOL-Based Phosphane-Phosphite Ligands in Enantioselective Cu-Catalyzed Grignard 1,4-Additions Followed by Mannich-Type Alkylations

Copper(I) complexes of TADDOL-based phosphanephosphite ligands catalyze enantioselective conjugate additions of various Grignard reagents to cyclic enones. Through trapping of the resulting chiral magnesium enolates with N-benzylidene-4-methylbenzenesulfonamide (as an imine) in one-pot procedures, the corresponding Mannich products (i.e., beta-aminocarbonyl compounds) were obtained in good yields and high enantiomeric purities, although with only low diastereoselectivities.