Application of N,S-chelating chiral ligands and zinc complexes in catalytic asymmetric hydrosilylation using polymethylhydrosiloxane

Gérard, Stéphane; Pressel, Yann; Riant, Olivier

doi:10.1016/j.tetasy.2005.04.025

Cited by 66 publications

(31 citation statements)

References 19 publications

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“…Introduction of two different chiral centers into the ligand gave rise to synergistic effects, leading to an increase of the enantioselectivity of hydrosilylation reaction. [25,26] Chiral N,S chelating ligands appear to be less effective in the zinc-catalyzed hydrosilylation of ketones; [27] however, recent results with the use of bis-tert-thiophenylmethyl derivative of DACH were promising (enantioselectivities up to 83% ee). [28] Finally, it has been found that ortho-multisubstituted benzophenones can be enantioselectivelly reduced (up to 96% ee of the product) with chiral di-A C H T U N G T R E N N U N G amine-Zn-diol complexes (chirality residing in the di-A C H T U N G T R E N N U N G amine part of the complex).…”

Section: Introductionmentioning

confidence: 99%

Convenient Enantioselective Hydrosilylation of Ketones Catalyzed by Zinc‐Macrocyclic Oligoamine Complexes

2009

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Chiral macrocyclic tetra-and hexamine macrocycles derived from trans-1,2-diaminocyclohexane (DACH) in complexes with diethylzinc efficiently catalyze the asymmetric hydrosilylation of aryl alkyl ketones with enantiomeric excess of the product up to 89%. The cyclic structure of the trianglamine ligand increases the enantioselectivity of the reaction, in comparison to the catalysis with the acyclic N,N'-dibenzyl-DACH ligand. Density functional theory (DFT) computations on the structures of ligand-zinc complexes and on the structures of these complexes with a coordinated acetophenone molecule allow us to rationalize the direction of the asymmetric induction of the hydrosilylation reaction as well as the superiority of the cyclic ligand compared to the acyclic one. This is the first example of asymmetric catalysis for the hydrosilylation reaction of ketones with the use of a readily available, inexpensive, and reusable macrocyclic trianglamine ligand.

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Section: Introductionmentioning

confidence: 99%

Convenient Enantioselective Hydrosilylation of Ketones Catalyzed by Zinc‐Macrocyclic Oligoamine Complexes

2009

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“…10 -Elimination was also proposed as an initiation step in a zinc-catalyzed ketone hydrosilylation. 11 Identification of conditions that favor or disfavor -H elimination in zinc(II) compounds may have important implications in group transfer reactions in synthetic and enzymatic chemistry. Here, we report a coordinatively saturated oxazolinylborato disilazidozinc(II) compound that undergoes a formal -H elimination at room temperature facilitated by LiCl.…”

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confidence: 99%

Conversion of a Zinc Disilazide to a Zinc Hydride Mediated by LiCl

2010

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An unusual β-elimination reaction involving zinc(II) and LiCl is reported. LiCl and a coordinatively saturated disilazido zinc compound form an adduct that contains activated SiH moieties. In THF/toluene mixtures, this adduct is transformed into a zinc hydride and 0.5 equiv. cyclodisilazane. The Li+ and Cl− ions apparently affect the reaction pathway of the disilazido zinc in a synergistic fashion. Thus, the zinc hydride and cyclodisilazane products of formal β-elimination are not observed upon treatment of the zinc disilazide with Cl− or Li+ separately.

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“…Most commonly, the reactions use zinc or copper catalysts in the presence of enantiopure ligands. In the case of zinc-catalyzed reactions, enantiopure diamine ligands are widely used (eqs 37 and 38), 59,64-68 although Pybox (pyridinebisoxazoline) or Pybim (pyridinebisimidazoline) ligands, 69 chelating N,S-ligands, 70 and thiourea ligands 71 have also been reported. When copper catalysis is employed, enantiopure phosphine ligands are usually used to introduce asymmetry.…”

Section: %mentioning

confidence: 99%