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• The polymer-immobilized chiral N-sulfonylated diamine ligands were prepared.
• The polymeric chiral Ru complexes were used as catalyst for asymmetric transfer hydrogenation.
• Hydrophobic polymeric catalysts performed very well in organic solvent such as CH2Cl2.
• Amphiphilic polymeric catalysts were efficiently used for the same asymmetric reaction in water.
Crosslinked polymers containing chiral N-sulfonylated diamine (TsDPEN) structure were synthesized by radical polymerization of chiral N1-(4-vinylbenzenesulfonyl)-1,2-diphenylethylene-1,2-diamine, divinylbenzene and achiral vinyl monomer. The polymer-immobilized chiral complex was prepared from the polymeric TsDPEN with ruthenium dichloride p-cymene. Asymmetric transfer hydrogenation of cyclic sulfonimine was performed using the polymer-immobilized TsDPEN–Ru (II) complex. The hydrophobic–hydrophilic balance of the polymers was tuned by means of the incorporation of the achiral vinyl monomers, which strongly influenced on the catalytic activity of the polymeric catalyst. In most cases the amphiphilic polymer-immobilized chiral catalysts are highly active in the asymmetric transfer hydrogenation. Enantioenriched sultam with up to 98% ee was obtained by using polymer-immobilized chiral catalysts containing quaternary ammonium salt in CH2Cl2. Some of the polymer-immobilized chiral catalysts containing quaternary ammonium salt were successfully used in water. Up to 95% ee was obtained by using the polymeric catalyst in water. Most of the quaternized polymeric catalysts showed sufficient reactivity and higher enantioselectivities compared with that of low-molecular-weight catalyst in water.
Amphiphilic polymer-immobilized chiral Ru complexes displayed excellent catalytic activity in asymmetric transfer hydrogenation of cyclic imines both in water and organic solvent.Figure optionsDownload as PowerPoint slide
Journal: Journal of Organometallic Chemistry - Volume 751, 1 February 2014, Pages 711–716