Enantio- and Diastereoselective Synthesis of β-Nitroalcohol via Henry Reaction Catalyzed by Cu(II), Ni(II), Zn(II) Complexes of Chiral BINIM Ligands

Abstract

Enantiopure Cu(II), Ni(II) and Zn(II) chiral complexes CuLR, CuLS, NiLR, NiLS, ZnLR and ZnLS were synthesised by using ligands LR and LS, which were derived from the (R)-(+)-1,1’-Binaphthyl-2,2′-diamine or (S)-(−)-1,1’-Binaphthyl-2,2’-diamine with pyridine-2-aldehyde. These six complexes are characterised and applied as a catalyst for asymmetric nitroaldol reaction. The enantiopure chiral ligand upon complexation transfers its chirality from ligand to metal and generate “Δ or Λ” chirality at the metal centre. All these associated chiral responses were monitored using circular dichroism. Ensuring the enantiopure nature of the complexes they have been demonstrated as an efficient enantioselective catalyst for nitroaldol reaction. Further, this asymmetric catalytic study has been extended to various nitroalkanes such as nitromethane, nitroethane and nitropropane with substituted benzaldehydes leading to the synthesis of various diastereoselective β-nitroalcohols.