Transfer hydrogenation reactions catalyzed by chiral half-sandwich Ruthenium complexes derived from Proline

Abstract

Chiral ruthenium half-sandwich complexes were prepared using a chelating diamine made from proline with a phenyl, ethyl, or benzyl group, instead of hydrogen on one of the coordinating arms. Three of these complexes were obtained as single diastereoisomers and their configuration identified by X-ray crystallography. The complexes are recyclable catalysts for the reduction of ketones to chiral alcohols in water. A ruthenium hydride species is identified as the active species by NMR spectroscopy and isotopic labelling experiments. Maximum enantio-selectivity was attained when a phenyl group was directly attached to the primary amine on the diamine ligand derived from proline.

Asymmetric transfer hydrogenation of ketones using Ru(0) nanoparticles modified by Chiral Thiones

“…ee determined using chiral HPLC, Chiralcel OD column . (ee given are mean of two values from two experiments, the error is less than (± 2).…”

“…Determined by HPLC using chiralcel OD column for all alcohols except those in entries 2, 3, 4 and 12 where chiralcel OJ‐H column was used, (ee given are mean of two values from two experiments, the error is less than (± 2).…”

“…HPLC was carried out on Waters 1525 Binary HPLC Pump attached with Waters 2487 Dual λ Absorbance Detector. The chiral columns used were Chiralcel OD column and chiralcel OJ‐H column . The absolute configuration of the products was determined using optical activity measurements.…”