Highly Efficient Asymmetric Additions of Diethylzinc to Aldehydes Triply Activated by Chiral Phosphoramide‐Zn(II) Complexes Derived From Cinchona Alkaloids

Abstract

New chiral phosphoramide ligands derived from cinchona alkaloids were developed, which react with diethylzinc to form chiral phosphoramide-Zn(II) complexes containing two Lewis bases and one Lewis acid. These trifunctional complexes can serve as highly efficient chiral catalysts for triple activation of enantioselective addition reactions of diethylzinc with aldehydes to give desired alcohol products with excellent yields and enantiomeric excess (ee) values up to 99%.

Catalytic asymmetric β-hydrogen transfer reduction of α-trifluoromethyl aromatic ketones with diethylzinc

“…[47][48][49][50][51] However, when trifluoromethylketone was used as the substrate, these ligands provided reduction alcohol product 5a as the main product and only a small amount of addition product 8 could be observed. The experimental results are listed in Table 1.…”

“…[47][48][49][50][51][52] This type of chiral ligands also shows high efficiency in organocatalyzed asymmetric reactions. [53][54][55][56] As part of our ongoing interest in developing efficient asymmetric reactions, we herein report the first asymmetric b-hydrogen transfer reduction of a-trifluoromethyl ketones with diethylzinc catalyzed by a 1,2-diamino phosphinamide chiral ligand derived from (1R,2R)-1,2-diphenylethylenediamine and its application in the chemo-and enantioselective reduction of methyl/trifluoromethyl diketone.…”

Asymmetric Synthesis of Diarylmethanols by Chiral Phosphoramide Ligands Catalysts

“…手性磷酰胺的配体 9c 的合成见 Scheme 1. Table 1 Screening of chiral ligand [18] , 8 [19] , 以及 9a, 9b 和 9d [17] 的合成参考文献方 法获得. [20] : m.p.…”

Chemo- and Enantioselective Addition and β-Hydrogen Transfer Reduction of Carbonyl Compounds with Diethylzinc Reagent in One Pot Catalyzed by a Single Chiral Organometallic Catalyst

“…Chiral 1,2-diamino phosphoramide ligands are very efficient in the catalytic asymmetric addition reactions of organozinc reagents to aldedhydes and ketones or organocatalyzed asymmetric reactions. − Our recent research findings showed that diethylzinc reagent could be used as a hydrogen source for the asymmetric β-H reduction of α-trifluoromethyl ketones in the presence of a catalytic ammount of chiral 1,2-diamino phosphoramide ligand L 1 , affording the corresponding reduction product with up to 88% yield and 73% enantioselectivity (Scheme ). As an effort to explore the application of chiral phosphoramide-Zn­(II) catalyzed asymmetric reactions, we herein report the one-pot catalytic asymmetric ethylation and enantioslective β-H transfer reduction of carbonyl compounds with a diethylzinc reagent using phosphoramide L 1 as a single chiral ligand.…”