A Catalytic Enantioselective Conjugate Addition of Cyanide to Enones

The first synthetically useful catalytic enantioselective conjugate addition of cyanide to enones is described. The optimized conditions involved a Gd catalyst (5 or 10 mol %) derived from ligands 3 or 4 and a 1:1 ratio of TBSCN and 2,6-dimethylphenol. The reaction exhibited excellent to high enantioselectivity and a wide substrate scope. Moreover, the 1,4-adduct was exclusively produced over the 1,2-adduct. The complete regioselectivity was due both to stabilization of the 1,4-selective silylated polymetallic catalyst (7) using a TBS group and the ability of the asymmetric catalyst to promote retro-cyanation from the 1,2-adduct.