Highly Diastereoselective Hydrogenation of Imines by a Bimetallic Pd−Cu Heterogeneous Catalyst (original) (raw)
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Advanced Synthesis & Catalysis, 2003
A range of aromatic and cyclic imines were subjected to asymmetric hydrogenation with catalysts derived from complexes of the type RuCl 2 (diphosphine)(diamine). Good to high enantioselectivities were observed. For each imine, a library of chiral complexes based on different diphosphine and dia-mine combinations was screened. A different combination of diphosphine and diamine was required each time to obtain the optimum enantioselectivity. N RuCl 2 (diphosphine)(diamine) HN 1 2 up to 94% ee (S/C/B = 100/1/100) overnight t-BuOK, i-PrOH 50 -65 °C, 15 bar H 2 , Scheme 1. Hydrogenation of N-(phenylethylidene)aniline (1).
Immobilized Chiral Metal Catalysts for Enantioselective Hydrogenation of Ketones
Mini-reviews in Organic Chemistry, 2008
Chiral secondary alcohols are useful synthetic building blocks. One direct approach to chiral secondary alcohols is by catalytic reduction of ketones using molecular hydrogen or by asymmetric transfer hydrogenation. This review focuses on recent developments using immobilized chiral metal catalysts, and their role in developing greener chemistry. Immobilization of chiral ligands on silica, polymer, dendrimer and magnetite nanoparticles and their application as catalyst with metals in the hydrogenation of ketones under environmentally friendly solvent conditions is discussed.
… 2011: Engineering a …, 2011
The hydrogenolysis of nitriles (R-C≡N) to the corresponding methyl compound (R-CH 3 ) is relatively uncommon. Generally, forcing conditions Watanabe, 1959, Weigert and or the use of a complicated or difficult to handle catalyst are required, while under mild conditions R-CH 3 generally occurs as a by-product of the hydrogenation of nitriles.(Bakker et al., 2010) However, we have performed the facile hydrogenolysis of not only various nitriles, but also of imines and amines over Pd/C using straightforward and relatively mild conditions (80 o C, 1 atm H 2 , in EtOH).
Enantioselective Hydrogenation Using Heterogeneous Modified Catalysts: An Update
Advanced Synthesis & Catalysis, 2003
The state of the art for the enantioselective hydrogenation applying chirally modified heterogeneous catalysts is reviewed with emphasis on new developments between 1997 and 2002. Discussed are various combinations of metal ± modifier ± substrate which give enantioselectivities useful for synthetic applications. The three most important asymmetric catalysts types are nickel catalysts modified with tartaric acid, useful for b-functionalized ketones with ees up to 98.6%, platinum catalysts modified with cinchona alkaloids and related modifiers, successful for a-functionalized ketones with ees up to 98% and palladium catalysts modified with cinchona alkaloids which achieve ees up to 94% for selected activated C C bonds. Mechanistic investigations comprising surface science and spectroscopic studies often combined with computational modeling as well as kinetic studies are summarized and the various mechanistic models are discussed. 1 Introduction 2 Nickel Catalysts Modified with Tartaric Acid and Related Catalysts 2.
Hydrogenation of chloronitrobenzenes over Pd and Pt catalysts supported on cationic resins
Chemical Papers, 2014
Liquid phase hydrogenation of chloronitrobenzene isomers (x-CNB x = 2, 3, 4) to the corresponding chloroanilines (x-CAN) at mild reaction conditions (0.6 MPa, 25 • C, diethyl ether-methanol as solvents) over palladium and platinum catalysts containing 1 mass % of metal on trimethylammonium functionalized poly{styrene-co-divinylbenzene} (Dowex-D) was studied. The average selectivities to x-CAN over Pd/D-Cl and Pd/D-OH catalysts were 72 % and 42 %, respectively, at the x-CNB conversion of about 80 %. The average selectivities of 81 % and 84 % were achieved using Pt/D-Cl and Pt/D-OH, respectively, at the x-CNB conversion of approximately 90 %, whereas the average starting reaction rates were 1.2 × 10 −3 mol g −1 s −1 and 2.6 × 10 −3 mol g −1 s −1 (hydrogen consumption rate per mass of platinum), respectively. Under similar reaction conditions, using palladium catalysts supported on a resin with anionic groups anchored to polymeric chains at the average reaction rate equal to 3.8 × 10 −3 mol g −1 s −1 (hydrogen consumption rate per mass of palladium), the selectivities from 85 % (2-CAN and 3-CAN) to 95 % (4-CAN) were achieved .