Ru-Tethered (R,R)-TsDPEN with DMAB as an efficient catalytic system for high enantioselective one-pot synthesis of chiral β-aminol via asymmetric transfer hydrogenation

Abstract

This work reflects Ru-tethered-TsDPEN as an active chiral catalyst for one pot selective synthesis of optically active α-substituted alcohols and its derivatives from α-bromo ketones in the presence of dimethylamine borane (DMAB) as the hydrogen source. Various Ru-chiral catalysts have been screened and the methodology proceeded via a (R,R) Ru-tethered TsDPEN catalyst through asymmetric transfer hydrogenation (ATH) of the in-situ formed ketones to the corresponding chiral β-aminol product. Thus, the Ru-tethered TsDPEN-DMAB catalytic system works efficiently with higher yield and high enantiomeric excess over others for the ATH process. Based on a study of ortho, meta and para substituted α-bromo acetophenone derivatives, effective enantioselectivity has been observed for ortho substituted β-aminol. The mechanism has been optimized depending on product analysis with the help of its kinetic AT-IR study. This work also focusses on the synthesis of various β-amino alcohol derivatives where the effect of an EWG and EDG on enantio-selectivity has been studied.