Synthesis, Characterization, and Study of Catalytic Activity of Chiral Cu(II) and Nickel(II) Salen Complexes in the α-Amino Acid C-α Alkylation ReactionстатьяИсследовательская статья
Статья опубликована в журнале из списка Web of Science и/или Scopus
Аннотация:A new family of Cu(II) and Ni(II) salen complexes was synthesized and fully characterized by various physicochemical methods. Their catalytic activity was evaluated in the phase-transfer С-alkylation reaction of the Schiff bases of D,L-alanine ester and benzaldehyde derivatives. It was found that the introduction of a chlorine atom into ortho- and para-position of the phenyl ring of the substrate resulted in an increase of both the chemical yield and the asymmetric induction (ee 66-98%). The highest enantiomeric excess was achieved in the case of a Cu(II) salen complex based on (S,S)-cyclohexanediamine and salicylaldehyde at -20 oC. The presence of a bulky substituent in the ligand present in the complexes led to a drastic decrease in ee and chemical yield. For instance, the introduction of bulky substituents at 3- and 5-positions of the phenyl ring of the catalyst resulted in a complete loss of the stereoselectivity control in the alkylation reaction.
