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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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Sch1:  

Mentions: Secondary alcohols are an important class of chiral building blocks in organic synthesis and form structural fragments of numerous biologically active compounds [1]. Major asymmetric catalytic methods for preparation of secondary alcohols rely mainly either on asymmetric hydrogenation of ketones, with use of chiral rhodium complexes as catalysts in both homogeneous and heterogeneous approaches, or on oxazaborolidine-catalyzed asymmetric reduction of ketones with diborane [2–6]. Before the re-invention of the reductive properties of polymethylhydrosiloxane (PMHS), a safe and inexpensive by-product of the silicon industry, hydrosilylation of C=O bonds seemed a less convenient method because of the toxicity and cost of monomeric silanes. Since the discovery of Zn-diamine-catalyzed asymmetric hydrosilylation of prochiral ketones, several other methods for enantioselective reduction of the C=O bonds have been developed [7–23]. They are mainly based on the use of chiral transition metal complexes with P,P-bidentate ligands, P,S-ligands, N-ligands, or N-heterocyclic carbene ligands. Although the enantioselectivity obtained by use of these complexes is >90 %, use of such complexes suffers from high cost and elaborate preparation. In contrast, use of catalytic systems based on zinc has emerged as a promising and advantageous method for metal-catalyzed asymmetric hydrosilylation of prochiral ketones (Scheme 1).Scheme 1


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

Sch1:  
Mentions: Secondary alcohols are an important class of chiral building blocks in organic synthesis and form structural fragments of numerous biologically active compounds [1]. Major asymmetric catalytic methods for preparation of secondary alcohols rely mainly either on asymmetric hydrogenation of ketones, with use of chiral rhodium complexes as catalysts in both homogeneous and heterogeneous approaches, or on oxazaborolidine-catalyzed asymmetric reduction of ketones with diborane [2–6]. Before the re-invention of the reductive properties of polymethylhydrosiloxane (PMHS), a safe and inexpensive by-product of the silicon industry, hydrosilylation of C=O bonds seemed a less convenient method because of the toxicity and cost of monomeric silanes. Since the discovery of Zn-diamine-catalyzed asymmetric hydrosilylation of prochiral ketones, several other methods for enantioselective reduction of the C=O bonds have been developed [7–23]. They are mainly based on the use of chiral transition metal complexes with P,P-bidentate ligands, P,S-ligands, N-ligands, or N-heterocyclic carbene ligands. Although the enantioselectivity obtained by use of these complexes is >90 %, use of such complexes suffers from high cost and elaborate preparation. In contrast, use of catalytic systems based on zinc has emerged as a promising and advantageous method for metal-catalyzed asymmetric hydrosilylation of prochiral ketones (Scheme 1).Scheme 1

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.