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Experimental and theoretical insights in the alkene – arene intramolecular π -stacking interaction

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ABSTRACT

Chiral acrylic esters derived from biomass were developed as models to have a better insight in the aryl–vinyl π-stacking interactions. Quantum chemical calculations, NMR studies and experimental evidences demonstrated the presence of equilibriums of at least four different conformations: π-stacked and face-to-edge, each of them in an s-cis/s-trans conformation. The results show that the stabilization produced by the π–π interaction makes the π-stacked conformation predominant in solution and this stabilization is slightly affected by the electron density of the aromatic counterpart.

No MeSH data available.


Intramolecular aryl–vinyl π-stacking interaction of a levoglucosenone derivative.
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Figure 1: Intramolecular aryl–vinyl π-stacking interaction of a levoglucosenone derivative.

Mentions: Noncovalent interactions have demonstrated to have relevant importance in chemistry and biology [1–4]. Considering all noncovalent interactions, π-stacking is perhaps the less well understood, although its application in materials sciences, enzyme design and template-directed synthesis have had a dramatic growth, mainly for arene–arene interactions [1–8]. In particular, the use of π–π overlap as an element of stereocontrol in highly selective chemical transformations has been widely explored [9]. In this context, as part of our continuous interest in the development of new tools for asymmetric synthesis using levoglucosenone (a biomass-derived chiral enone) [10–15], we reported the synthesis of a novel chiral auxiliary that demonstrated to be very efficient in an asymmetric Diels–Alder reaction between the acrylic ester derivative and cyclopentadiene [16]. The facial selectivity of this reaction proved to be due to an aryl–vinyl π-stacking intramolecular interaction that fixed the conformation of the dienophile (Fig. 1) [16].


Experimental and theoretical insights in the alkene – arene intramolecular π -stacking interaction
Intramolecular aryl–vinyl π-stacking interaction of a levoglucosenone derivative.
© Copyright Policy - Beilstein
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4979656&req=5

Figure 1: Intramolecular aryl–vinyl π-stacking interaction of a levoglucosenone derivative.
Mentions: Noncovalent interactions have demonstrated to have relevant importance in chemistry and biology [1–4]. Considering all noncovalent interactions, π-stacking is perhaps the less well understood, although its application in materials sciences, enzyme design and template-directed synthesis have had a dramatic growth, mainly for arene–arene interactions [1–8]. In particular, the use of π–π overlap as an element of stereocontrol in highly selective chemical transformations has been widely explored [9]. In this context, as part of our continuous interest in the development of new tools for asymmetric synthesis using levoglucosenone (a biomass-derived chiral enone) [10–15], we reported the synthesis of a novel chiral auxiliary that demonstrated to be very efficient in an asymmetric Diels–Alder reaction between the acrylic ester derivative and cyclopentadiene [16]. The facial selectivity of this reaction proved to be due to an aryl–vinyl π-stacking intramolecular interaction that fixed the conformation of the dienophile (Fig. 1) [16].

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Chiral acrylic esters derived from biomass were developed as models to have a better insight in the aryl–vinyl π-stacking interactions. Quantum chemical calculations, NMR studies and experimental evidences demonstrated the presence of equilibriums of at least four different conformations: π-stacked and face-to-edge, each of them in an s-cis/s-trans conformation. The results show that the stabilization produced by the π–π interaction makes the π-stacked conformation predominant in solution and this stabilization is slightly affected by the electron density of the aromatic counterpart.

No MeSH data available.