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Asymmetric hydrosilylation of ketones catalyzed by complexes formed from trans-diaminocyclohexane-based diamines and diethylzinc.

Gajewy J, Gawronski J, Kwit M - Monatsh. Chem. (2012)

Bottom Line: Chiral acyclic and macrocyclic amines derived from trans-1,2-diaminocyclohexane in complexes with diethylzinc efficiently catalyze asymmetric hydrosilylation of aryl-alkyl and aryl-aryl ketones with enantiomeric excess of the product up to 86 %.A trianglamine ligand with a cyclic structure or the presence of an additional coordinating group increases the enantioselectivity of the reaction, in comparison with catalysis by a simple acyclic N,N'-dibenzyl-1,2-diaminocyclohexane ligand.In addition, the effect of the asymmetric activation of the catalyst by a variety of alcohols and diols is studied.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, A. Mickiewicz University, 60-780 Poznan, Poland.

ABSTRACT

Abstract: Chiral acyclic and macrocyclic amines derived from trans-1,2-diaminocyclohexane in complexes with diethylzinc efficiently catalyze asymmetric hydrosilylation of aryl-alkyl and aryl-aryl ketones with enantiomeric excess of the product up to 86 %. A trianglamine ligand with a cyclic structure or the presence of an additional coordinating group increases the enantioselectivity of the reaction, in comparison with catalysis by a simple acyclic N,N'-dibenzyl-1,2-diaminocyclohexane ligand. In addition, the effect of the asymmetric activation of the catalyst by a variety of alcohols and diols is studied.

No MeSH data available.


 
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Sch2:  

Mentions: Introduction of two different chiral centers into the ligand structure may give rise to synergistic effects, leading to and increase in the enantioselectivity of hydrosilylation reaction [34]. The basic concept consists in the idea of “asymmetric activation”, introduced by Mikami and co-workers and subsequently applied to several enantioselective transformations [35–39]. By following this concept, Ushio and Mikami have developed an efficient method for hydrosilylation of ortho-substituted benzophenones by use of chiral [Zn(diamine)(diol)] complexes, with chirality residing in the diamine part of the complex (Scheme 2) [38]. Prochiral benzophenones can be enantioselectively reduced with up to 96 % ee of the product. The effect of an activator on the stereochemistry of the product was negligible, because enantioselectivity was comparable irrespective of whether (R) or (S)-BINOL, or ethylene glycol was used.Scheme 2


Asymmetric hydrosilylation of ketones catalyzed by complexes formed from trans-diaminocyclohexane-based diamines and diethylzinc.

Gajewy J, Gawronski J, Kwit M - Monatsh. Chem. (2012)

 
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4494764&req=5

Sch2:  
Mentions: Introduction of two different chiral centers into the ligand structure may give rise to synergistic effects, leading to and increase in the enantioselectivity of hydrosilylation reaction [34]. The basic concept consists in the idea of “asymmetric activation”, introduced by Mikami and co-workers and subsequently applied to several enantioselective transformations [35–39]. By following this concept, Ushio and Mikami have developed an efficient method for hydrosilylation of ortho-substituted benzophenones by use of chiral [Zn(diamine)(diol)] complexes, with chirality residing in the diamine part of the complex (Scheme 2) [38]. Prochiral benzophenones can be enantioselectively reduced with up to 96 % ee of the product. The effect of an activator on the stereochemistry of the product was negligible, because enantioselectivity was comparable irrespective of whether (R) or (S)-BINOL, or ethylene glycol was used.Scheme 2

Bottom Line: Chiral acyclic and macrocyclic amines derived from trans-1,2-diaminocyclohexane in complexes with diethylzinc efficiently catalyze asymmetric hydrosilylation of aryl-alkyl and aryl-aryl ketones with enantiomeric excess of the product up to 86 %.A trianglamine ligand with a cyclic structure or the presence of an additional coordinating group increases the enantioselectivity of the reaction, in comparison with catalysis by a simple acyclic N,N'-dibenzyl-1,2-diaminocyclohexane ligand.In addition, the effect of the asymmetric activation of the catalyst by a variety of alcohols and diols is studied.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, A. Mickiewicz University, 60-780 Poznan, Poland.

ABSTRACT

Abstract: Chiral acyclic and macrocyclic amines derived from trans-1,2-diaminocyclohexane in complexes with diethylzinc efficiently catalyze asymmetric hydrosilylation of aryl-alkyl and aryl-aryl ketones with enantiomeric excess of the product up to 86 %. A trianglamine ligand with a cyclic structure or the presence of an additional coordinating group increases the enantioselectivity of the reaction, in comparison with catalysis by a simple acyclic N,N'-dibenzyl-1,2-diaminocyclohexane ligand. In addition, the effect of the asymmetric activation of the catalyst by a variety of alcohols and diols is studied.

No MeSH data available.