Ru‐TsDPEN catalysts and derivatives in asymmetric transfer hydrogenation reactions

Abstract

This review summarizes current developments, novel synthetic routes for Ruthenium tethered chiral catalyst, and its derivatives along with its application in asymmetric synthesis. The review also covers derivatization in tethering unit, modification in N-monofunctionalized ligand as well as ligation of other ligand with Ru metal in chiral catalyst. Apparently, the effect of a modified tethered catalyst in the enantioselective synthesis of chiral products as well as in synthetic chemistry is also discussed in detail.

Asymmetric hydrogenation and transfer hydrogenation in the enantioselective synthesis of flavonoids

“…Furthermore, asymmetric hydrogenation (AH) 27–34 and asymmetric transfer hydrogenation (ATH) 35–44 have arisen as potent methodologies for the preparation of chiral compounds. As a result, they have been extensively explored in the synthesis of a variety of natural scaffolds and pharmaceutics.…”

Diastereoselective synthesis of a cyclic diamide‐bridged biphenyl as chiral atropos ligand

“…12,13 To date, Noyori's catalyst and structurally similar compounds are among the most widely used catalysts for asymmetric transfer hydrogenations. 14,15 The concept of chiral activation can provide highly activated catalysts for asymmetric transformations by inducing a ligand acceleration or modification. 16 Furthermore, tropos biphenyl derived ligands enable the synthesis of supramolecular catalysts, which can switch their sense of chirality by interaction with their own reaction product and therefore lead to asymmetric amplification and nonlinear effects.…”

“… 11 This results in ee's of up to 99% for a large variety of aromatic ketones 12,13 . To date, Noyori's catalyst and structurally similar compounds are among the most widely used catalysts for asymmetric transfer hydrogenations 14,15 . The concept of chiral activation can provide highly activated catalysts for asymmetric transformations by inducing a ligand acceleration or modification 16 .…”

Asymmetric Transfer Hydrogenation of α-Keto Amides; Highly Enantioselective Formation of Malic Acid Diamides and α-Hydroxyamides

“…The asymmetric transfer hydrogenation (ATH) of ketones using Noyori–Ikariya catalysts, including their tethered derivatives e.g., 1 – 4 (Figure ), has been widely reported, notably for acetophenone derivatives and acetylenic and fluorinated ketones. − In contrast, the ATH of α-keto amides has not been explored in detail, even though they are useful intermediates toward pharmaceutical targets and ligands for asymmetric catalysis . A report by Bhanage and Mishra, using the 3C tethered catalyst 2 , demonstrated a practical approach to the synthesis of asymmetric mandelimides, (Figure A).…”

“…For ATH reactions, we employed the “3C-tethered” catalyst ( R , R )- 2 that we have previously applied to ATH reactions. Formic acid–triethylamine 5:2 azeotrope (FA/TEA) was used as the reducing agent, with reactions carried out at rt using 1.5 mol % of catalyst, with dichloromethane (DCM) to improve substrate solubility . In the first series, for consistency, the distal amide was the N -methyl- N -phenyl derivative in most cases (Figure ).…”