Preparation of the enantiopure 1,2‐diamine monomer and its polymerization: The efficient polymeric chiral ligand of an asymmetric hydrogenation catalyst

Abstract

AbstractAn enantiopure 1,2‐diamine monomer possessing a p‐vinylbenzyl group as a polymerizable group was synthesized from chiral 1,2‐bis(p‐hydroxyphenyl)‐N,N′‐bis(tert‐butoxycarbonyl)‐1,2‐diaminoethane. The chiral monomer was copolymerized with styrene, and this was followed by the deprotection of the tert‐butoxycarbonyl group, which yielded the polymer‐supported chiral 1,2‐diamine. The polymeric catalyst system was established with the polymeric chiral 1,2‐diamine complexed with 2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl/RuCl2. In the presence of potassium tert‐butoxide (t‐BuOK), the polymeric catalyst system worked well in the asymmetric hydrogenation of aromatic ketones. The corresponding chiral secondary alcohols were obtained in quantitative yields with a high level of enantioselectivity. The insolubility of the catalyst, caused by the crosslinked structure of the polymer, made it recyclable. The polymeric catalyst was reused several times without a loss of catalytic activity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4556–4562, 2004