Asymmetric hydrogenation of aromatic ketones using polymeric catalyst prepared from polymer-supported 1,2-diamine

tert-Butyloxycarbonyl (Boc) protected chiral 1,2-diamine monomers 3 were copolymerized with achiral vinyl monomers such as styrene, methacrylates, acrylates, methacrylamide, and acrylamide to give crosslinked polymers P2 containing chiral 1,2-diamine moieties. Deprotection of the Boc groups in the polymer afforded the crosslinked chiral 1,2-diamine polymer P3. The diamine polymer was allowed to react with RuCl2/BINAP in DMF to form polymeric complex. Asymmetric hydrogenation of aromatic ketones smoothly proceeded using the polymeric complex to give the corresponding secondary alcohol in quantitative yield with high level of enantioselectivity up to 98% ee in a mixed solvent of DMF and 2-propanol. The polymeric catalyst can be recycled several times without loss of the activity.

Graphical abstractThe polymer-supported chiral 1,2-diamines were synthesized by copolymerization of the chiral 1,2-diamine monomer and various kinds of achiral monomers. The asymmetric hydrogenation of aromatic ketones with polymer-supported catalyst prepared from the polymeric chiral 1,2-diamine ligand leads to the corresponding secondary alcohols in quantitative yield with high level of enantioselectivity.Figure optionsDownload full-size imageDownload as PowerPoint slide