Synthesis of imine group containing chiral BIS (Phosphinite) ligands and Ru(II) complexes: Investigation of their catalytic activity in the asymmetric transfer hydrogenation of ketones
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Tarih
2016
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info:eu-repo/semantics/openAccess
Özet
Transfer hydrogenation processes are attracting considerable attention in synthetic chemistry due to their operational simplicity. Asymmetric transfer hydrogenation of simple ketones by using chiral catalysts is one of the most significant ways to obtain chiral alcohols in organic synthesis. The most popular ligands employed in asymmetric catalysis are phosphorus containing ones. The common feature of the ligands used for this purpose is to have a C2 symmetry axis. Although there have been many reports on these type ligands and their transition metal complexes, to the best of our knowledge, there are few studies on imine containing bis(phosphinites) and their catalytic activity in asymmetric transfer hydrogenation. In the present study, firstly, 1-({[(1R,2R)-2-{[(2-hydroxynaphthalen-1-yl)methylidene] amino}cyclohexyl]imino}methyl)naphthalen-2-ol was prepared as precursors for phosphinites according to a literature procedure. Then, new chiral C2-symmetric bis(phosphinite) ligands were synthesized the corresponding 1-({[(1R,2R)-2-{[(2-hydroxynaphthalen-1- yl)methylidene]amino}cyclohexyl] imino} methyl)naphthalen-2-ol and two equivalents of (Cy)2PCl, PPh2Cl or P(i-Pr)2Cl in high yields. Ru(II) metal complexes of the chiral phosphinite ligands were synthesized by treating of [Ru(?6 -p-cymene)(?-Cl)Cl]2 with the phosphinites in 1:1 molar ratio in CH2Cl2 and their catalytic activity in asymmetric transfer hydrogenation were investigated in the reaction of acetophenone derivatives with isopropyl alcohol. Keywords: Asymmetric transfer hydrogenation, Phosphinite, Catalysis, Ruthenium, Chirality
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Asymmetric transfer hydrogenation, Phosphinite, Catalysis, Catalysis, Ruthenium, Chirality
