Polymeric Micelles with Chiral Diamine-Ru(II) Catalysts for Asymmetric Transfer Hydrogenation of Ketones in Water

Abstract

Chiral aromatic alcohols with unique structures have attracted wide attention in asymmetric catalysis for decades. In this study, polymeric micelles with chiral diamine-Ru(II) catalysts in the hydrophobic core for asymmetric transfer hydrogenation of ketones affording chiral aromatic alcohols were presented. Firstly, block polymers with (1R,2R)-(+)-1,2-diphenyl ethylenediamine (DPEN) in the branched chain were successfully synthesized by Ring-Opening Metathesis Polymerization (ROMP) using 1,1-dimethylethyl N-(2amino-1,2-diphenylethyl) carbamate (NB-DPEN-Boc) and polyethylene glycol (NB-PEG2000) with norbornene groups as raw materials. The structures of block polymers P(DPEN)-co-P(PEG2000) were characterized by FT-IR and 1 H NMR. Next, Block polymers with chiral DPEN ligand in the branched chain coordinate with [RuCl2(p-cymene)]2 to provide amphiphilic polymers with chiral diamine-Ru(II) catalyst.Then, the self-assembly of the amphiphilic polymers in water produced the polymeric micelles with chiral diamine-Ru(II) catalysts in the hydrophobic core. The particle sizes were found to be 65 nm by DLS analysis. The polymeric micelles as catalytic nanoreactors were successfully applied in the asymmetric transfer hydrogenation (ATH) of various ketones in water. The heterogenization of homogeneous catalysts and construction of catalysts for aqueous catalysis demonstrate potential application prospects in the preparation of chiral aromatic alcohols.

Application of chiral recyclable catalysts in asymmetric catalysis

“…In 2022, Jia et al successfully synthesized a star-shaped thermal responsive polymer 11 via ATRP polymerization (Scheme 11). 49,50 The resulting polymer was immobilized onto a chiral metal–organic catalyst prepared using Ru metal and chiral diamine ligands, with the chiral ligand coordinating with Cu 2+ metal. The research revealed that the interaction between the chiral polymer and Cu 2+ results in the emergence of a chiral amplification phenomenon.…”