Limits...
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.


Structures of stable conformers L8 ZnMe2 (a) and L8 ZnMe2 (b) calculated at the PBE0/6-311++G(d,p) level of theory (some hydrogen atoms were omitted for clarity; distances are in Å)
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4494764&req=5

Fig4: Structures of stable conformers L8 ZnMe2 (a) and L8 ZnMe2 (b) calculated at the PBE0/6-311++G(d,p) level of theory (some hydrogen atoms were omitted for clarity; distances are in Å)

Mentions: Efficiency of the catalyst may be further tuned by introduction of additional coordinating groups, although with varying results. Replacement of the phenyl group by a 2-pyridyl group (L11) results in an increase of conversion at the expense of enantioselectivity (52 %), in comparison with L2 (Fig. 3, entry 11). Introduction of a diphenylphosphine group in the ligand L10 structure results in an increase of enantioselectivity (to 72 %; Fig. 3, entry 10), but enantioselectivity is still lower than with use of L2. The best result in terms of product enantioselectivity (86 %) and conversion of the substrate (>99 %) was obtained by use of methoxy-substituted ligand L8 (Fig. 3, entry 8). Direct (Me)O···Zn interactions are excluded in the complex of L8 and dialkylzinc. According to computation at the PBE0/6-311++G(d,p) level [45] the stable conformer L8 ZnMe2 (Fig. 4b), in which a direct O···Zn interaction is possible, is of higher energy (19.7 kJ mol−1) than the conformer with an intramolecular NH···O(Me) hydrogen bond (Fig. 4).Fig. 4


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

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

Structures of stable conformers L8 ZnMe2 (a) and L8 ZnMe2 (b) calculated at the PBE0/6-311++G(d,p) level of theory (some hydrogen atoms were omitted for clarity; distances are in Å)
© Copyright Policy
Related In: Results  -  Collection

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

Fig4: Structures of stable conformers L8 ZnMe2 (a) and L8 ZnMe2 (b) calculated at the PBE0/6-311++G(d,p) level of theory (some hydrogen atoms were omitted for clarity; distances are in Å)
Mentions: Efficiency of the catalyst may be further tuned by introduction of additional coordinating groups, although with varying results. Replacement of the phenyl group by a 2-pyridyl group (L11) results in an increase of conversion at the expense of enantioselectivity (52 %), in comparison with L2 (Fig. 3, entry 11). Introduction of a diphenylphosphine group in the ligand L10 structure results in an increase of enantioselectivity (to 72 %; Fig. 3, entry 10), but enantioselectivity is still lower than with use of L2. The best result in terms of product enantioselectivity (86 %) and conversion of the substrate (>99 %) was obtained by use of methoxy-substituted ligand L8 (Fig. 3, entry 8). Direct (Me)O···Zn interactions are excluded in the complex of L8 and dialkylzinc. According to computation at the PBE0/6-311++G(d,p) level [45] the stable conformer L8 ZnMe2 (Fig. 4b), in which a direct O···Zn interaction is possible, is of higher energy (19.7 kJ mol−1) than the conformer with an intramolecular NH···O(Me) hydrogen bond (Fig. 4).Fig. 4

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.