Enantioselective Michael Addition Reaction Catalysed by Enantiopure Binuclear Nickel(II) Close‐Ended Helicates

Abstract

Abstract The enantiopure Ni(II) helicates [Ni 2 L 1 RR .Cl 2 ] ( 1 ), [Ni 2 L 1 SS .Cl 2 ] ( 1′ ), [Ni 2 L 2 RR .Cl 2 ] ( 2 ), [Ni 2 L 2 SS .Cl 2 ] ( 2′ ) were synthesized by one‐pot self‐assembly technique from R ‐(+)‐ or S ‐(−)‐1,1′‐binaphthyl‐2,2′‐diamine, with 4‐methyl‐2,6‐diformyl phenol or 4‐ tert ‐butyl‐2,6‐diformyl phenol and nickel salts. This binuclear double stranded Ni(II) helicates were characterized by ESI‐MS, IR and single crystal X‐ray structure wherever applicable. The extensive chiroptical studies suggest that the complexes are enantiopure in nature. The chirality transfer from ligand L 1 RR & L 2 RR to Ni(II) metal centre produced ΔΔ geometrical chirality, while their enantiomeric counterpart L 1 SS & L 2 SS produced ΛΛ chirality in their respective complexes.These enantiopure helicates were applied as catalysts in asymmetric Michael addition of 1,3‐dicarbonyl compounds with β‐nitrostyrene to produce nitroalkanes in good yield (96–98%) and ee (78–94%). magnified image