Scope and Mechanism of Enantioselective Michael Additions of 1,3-Dicarbonyl Compounds to Nitroalkenes Catalyzed by Nickel(II)−Diamine Complexes

Readily prepared Ni(II)-bis[(R,R)-N,N‘-dibenzylcyclohexane-1,2-diamine]Br2 was shown to catalyze
the Michael addition of 1,3-dicarbonyl compounds to nitroalkenes at room temperature in good yields with
high enantioselectivities. The two diamine ligands in this system each play a distinct role:  one serves as
a chiral ligand to provide stereoinduction in the addition step while the other functions as a base for substrate
enolization. Ligand modification within the catalyst was also investigated to facilitate the reaction of aliphatic
nitroalkenes, 1,3-diketones, and β-ketoacids. Ni(II)-bis[(R,R)-N,N‘-di-p-bromo-benzylcyclohexane-1,2-diamine]Br2 was found to be an effective catalyst in these instances. Furthermore, monodiamine complex,
Ni(II)-[(R,R)-N,N‘-dibenzylcyclohexane-1,2-diamine]Br2, catalyzed the addition reaction in the presence of
water. The proposed model for stereochemical induction is shown to be consistent with X-ray structure
analysis.