New bis(1-ferrocenylethyl)amine-derived monodentate phosphoramidite ligands for highly enantioselective copper-catalyzed 1,4-conjugate addition

A new family of chiral bis(1-ferrocenylethyl)amine-derived monodentate phosphoramidite ligands has been prepared and successfully applied in the Cu-catalyzed asymmetric 1,4-conjugate addition of diethylzinc to a variety of α,β-unsaturated compounds, in which up to 99% ee was obtained for nitroalkenes at −78 °C and >98% ee for cyclohexenone at −30 °C, comparable to or higher than those obtained with the most efficient monophosphoramidite ligands reported so far.

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Bis[(R)-1-ferrocenylethyl]amineC24H27Fe2N
• Ee >98%
• [α]D20=-69.4 (c 0.30, CHCl3)
• Source of chirality: N,N-dimethyl-(R)-1-ferrocenylethylamine
• Absolute configuration: (R,R)

O,O′-(R)-(1,1′-Dinaphthyl-2,2′-diyl)-N,N′-di(R,R)-1-ferrocenylethylphosphoramiditeC44H39Fe2NO2PEe >98%[α]D25=-581 (c 0.598, CHCl3)Source of chirality: (R)-BINOL, bis(1-ferrocenylethyl)amineAbsolute configuration: (R,R,R)

O,O′-(S)-(1,1′-Dinaphthyl-2,2′-diyl)-N,N′-di(R,R)-1-ferrocenylethylphosphoramiditeC44H39Fe2NO2PEe >98%[α]D25=-42 (c 0.518, CHCl3)Source of chirality: (S)-BINOL, bis(1-ferrocenylethyl)amineAbsolute configuration: (S,R,R)