Asymmetric Hydrosilylation Of Ketones Research Articles

ChemInform Abstract: Iron‐ and Cobalt‐Catalyzed Asymmetric Hydrosilylation of Ketones and Enones with Bis(oxazolinylphenyl)amine Ligands.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Rhodium-Catalyzed Asymmetric Hydrosilylation of Ketones Employing a New Ligand Embodying the Bis(oxazolinyl)pyridine Moiety

A general approach to new ligands embodying bis(oxazolinyl)pyridine has been developed, employing palladium-catalyzed Suzuki coupling and base-mediated cyclization as pivotal steps. A rhodium catalyst derived from the ligand 4-(4-ethylphenyl)-2,6-bis(4-isopropyl-4,5-dihydrooxazol-2-yl)pyridine gave excellent enantioselectivity in the asymmetric hydrosilylation of ketones. In addition the electronic effect of remote substituents on the catalytic activity of rhodium catalyst was studied.

ChemInform Abstract: Recent Progress in the Asymmetric Hydrosilylation of Ketones and Imines

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Iron‐ and Cobalt‐Catalyzed Asymmetric Hydrosilylation of Ketones and Enones with Bis(oxazolinylphenyl)amine Ligands

Chiral bis(oxazolinylphenyl)amines proved to be efficient auxiliary ligands for iron and cobalt catalysts with high activity for asymmetric hydrosilylation of ketones and asymmetric conjugate hydrosilylation of enones.

Mechanistic Studies on the Copper‐Catalyzed Hydrosilylation of Ketones

AbstractThe copper‐catalyzed asymmetric hydrosilylation of ketones is an efficient method for the synthesis of chiral enantiopure secondary alcohols. Herein, we present a detailed computational study (DFT/B3LYP) of the copper(I)‐catalyzed reaction. In particular, the two transition states involved in the catalytic cycle have been determined. The insertion of the ketone into the Cu–H bond was found to have a lower activation barrier than the reaction of the copper alkoxy intermediate with the silane, which regenerates Cu–H along with the silyl ether product. Our findings also reveal the importance of the copper hydride dimer in controlling the reactivity toward the ketone. The conclusions are supported by experimental mechanistic investigations including kinetic studies, kinetic isotope effect, and isotope labeling measurements.

ChemInform Abstract: Asymmetric Hydrosilylation of Ketones Catalyzed by Magnetically Recoverable and Reusable Copper Ferrite Nanoparticles.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Asymmetric Hydrosilylation of Ketones by Copper Ferrite Nanoparticles

Asymmetric Hydrosilylation of Ketones by Copper Ferrite Nanoparticles

Recent Progress in the Asymmetric Hydrosilylation of Ketones and Imines

The asymmetric hydrosilylation of ketones and imines has seen significant advances in the last decade. The discovery of new highly efficient catalysts has turned this catalytic process into an attractive method for practical applications. Impressive chemical yields and enantioselectivities have been attained employing newly designed catalytic systems based on rhodium, copper, zinc and iron with suitable bidentate chiral ligands.

Asymmetric Hydrosilylation of Ketones Catalyzed by Magnetically Recoverable and Reusable Copper Ferrite Nanoparticles

Herein we present magnetically recoverable and reusable copper ferrite nanoparticles for asymmetric hydrosilylation of several ketones. Up to 99% enantiometric excess was obtained at room temperature using polymethylhydrosiloxane as the stoichiometric reducing agent. The copper ferrite nanoparticles were magnetically separated, and the efficiency of the catalyst remains almost unaltered up to three cycles.

A novel planar chiral N-heterocyclic carbene–oxazoline ligand for the asymmetric hydrosilylation of ketones

Abstract A novel ferrocene-based planar chiral N -heterocyclic carbene–oxazoline ligand was synthesized and applied to the rhodium(I)-catalyzed asymmetric hydrosilylation of ketones. Moderate catalytic activity and enantioselectivity were obtained.

Rhodium‐Catalyzed Asymmetric Hydrosilylation of Ketones Using HETPHOX Ligands.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Competitive Substitution Reactions at Extracoordinate Silicon during Asymmetric Hydrosilylation

Proline-derived small molecules were utilized as organic catalysts in the asymmetric hydrosilylation of ketones. Extracoordinate chiral hydrosilicates were generated in situ as shown by 29Si NMR. These active species reduce prochiral ketones enantioselectively in good yield but only moderate enantiomeric excess (up to 40%). The parameters affecting stereoselectivity have been studied in detail. By isolating some of the intermediates and performing a series of control reactions, the relative efficiency of alkoxy group exchange reactions and the ability of ketones to complex to extracoordinate hydrosilicates have been discovered to be critical factors. The proline catalyst is a poorer leaving group from the initial pentacoordinate product than the product of reduction, PhMeCHO-, which leads subsequently to several competitive hydrosilylation pathways.

The development of an enantioselective nickel hydrosilylation catalyst system via multi-substrate screening

Multi-substrate screening (asymmetric hydrosilylation of ketones) comparing the catalytic behaviour of Ru, Ni, Pd, Rh and Ir DIOP-catalyst systems [DIOP = O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane] was performed. Initial screening studies revealed that beside the well explored rhodium complexes nickel-based catalysts show interesting selectivity and activity. Mechanistic studies indicate a long induction period in which the active and selective catalyst is formed. [Ni(DIOP) 2] which X-ray crystal structure was determined is not active under the applied conditions. Optimisation of the catalyst behaviour concluded from the mechanistic studies led to an improvement of the enantioselectivity by around 20% in comparison to the multi-substrate screening results.

Furanoside Thioether—Phosphinite Ligands for Rh‐Catalyzed Asymmetric Hydrosilylation of Ketones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Organocatalytic Asymmetric Hydrosilylation of Ketones and Ketimines

Organocatalytic asymmetric hydrosilylations are reported. Chiral isochinolyloxazoline 1 mediates the reduction of both aromatic ketones 2 and aromatic ketimines 4 with trichlorosilane to give the corresponding alcohols 3 and amines 5 in good yields and enantioselectivities. Mechanistic considerations based on the interpretation of experimental data and computational investigations are also provided. The observed chiral induction is presumed to result from aromatic interactions between catalyst 1 and prochiral substrates 2 and 4.

Phosphite–oxazoline ligands for Rh-catalyzed asymmetric hydrosilylation of ketones

A series of phosphite–oxazoline ligands was tested in the Rh-catalyzed hydrosilylation of ketones. Systematic variation of the electronic and steric properties at the biphenyl phosphite moiety and at the oxazoline moiety provide useful information about the ligand parameters that control the enantiodiscrimination. The results show that the enantiomeric excesses are dependent on the properties on both the phosphite and oxazoline moieties of the ligand and on steric and electronic properties of the substrate. Low-to-moderate enantiomeric excesses (up to 62%) were obtained in the hydrosilylation of several aryl ketones.

Furanoside thioether–phosphinite ligands for Rh-catalyzed asymmetric hydrosilylation of ketones

A series of thioether–phosphinite ligands, easily prepared in a few steps from inexpensive d-(+)-xylose, were tested in the Rh-catalyzed hydrosilylation of ketones. Systematic variation of the electronic and steric properties of the thioether moiety provided useful information about the ligand parameters which control enantiodiscrimination. The results show that the enantiomeric excesses are strongly dependent on the steric properties of the substituent on the thioether moiety and on the steric properties of the substrate. High activities and good enantiomeric excesses (up to 90%) were obtained in the hydrosilylation of several aryl ketones.

Bis‐paracyclophane N‐Heterocyclic Carbene—Ruthenium Catalyzed Asymmetric Ketone Hydrosilylation.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Recent Advances in the Asymmetric Hydrosilylation of Ketones, Imines and Electrophilic Double Bonds

AbstractFor Abstract see ChemInform Abstract in Full Text.

Bis-paracyclophane N-heterocyclic carbene–ruthenium catalyzed asymmetric ketone hydrosilylation

New chiral bis-paracyclophane N-heterocyclic carbene (NHC) ligands 1– 3 have been explored for ruthenium catalyzed asymmetric hydrosilylation of ketones using diphenylsilane to give enantioenriched alcohols. These ligands provide for efficient asymmetric reduction in the presence of silver(I) triflate (1 mol %) at room temperature with high reactivity and selectivity. Acetophenone 4 was reduced with 1 mol % catalyst in 96% isolated yield, 97% ee. Following removal of the silyl ether, various alcohols 5 were obtained from aromatic ketones in high yield and selectivity.