Crystal structure and dynamic NMR studies of octaacetyl-tetra(propyl)calix[4]resorcinarene

Velásquez-Silva, Astrid; Baker, Brian; Rivera‐Monroy, Zuly Jenny; Pérez‐Redondo, Adrián; Maldonado, Mauricio

doi:10.1016/j.molstruc.2017.02.059

Cited by 26 publications

(22 citation statements)

References 38 publications

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“…The exchange rate constants were analysed by means of Eyring plots (see the Supporting Information), which provided Gibbs free energies of activation (Δ G ≠ 298 ) of 55.5 kJ mol −1 for 1 and 52.0 kJ mol −1 for 2 (Table ). These values are similar to the value obtained for octa‐acetylated resorcinarene podands (Δ G ≠ 298 =54.7 kJ mol −1 ) …”

Section: Resultssupporting

confidence: 88%

Correlating Solution‐ and Solid‐State Structures of Conformationally Flexible Resorcinarenes: Significance of a Sulfonyl Group in Intramolecular Self‐Inclusion

Pamuła

Nissinen

Helttunen

2020

Chemistry A European J

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The synthesis of tetramethoxyresorcinarene podands bearing p‐toluene arms connected by ‐SO3‐ (1) and ‐CH2O‐ (2) linkers is presented herein. In the solid state, the resorcinarene podand 1 forms an intramolecular self‐inclusion complex with the pendant p‐toluene group of a podand arm, whereas the resorcinarene podand 2 does not show self‐inclusion. The conformations of the flexible resorcinarene podands in solution were investigated by variable‐temperature experiments using 1D and 2D NMR spectroscopic techniques as well as by computational methods, including a conformational search and subsequent DFT optimisation of representative structures. The 1H NMR spectra of 1 and 2 at room temperature show a single set of proton signals that are in agreement with C4v symmetry. At low temperatures, the molecules exist as a mixture of boat conformations featuring slow exchange on the NMR timescale. Energy barriers (ΔG≠298) of 55.5 and 52.0 kJ mol−1 were calculated for the boat‐to‐boat exchange of 1 and 2, respectively. The results of the ROESY experiments performed at 193 K and computational modelling suggest that in solution the resorcinarene podand 1 adopts a similar conformation to that present in its crystal structure, whereas podand 2 populates a more versatile range of conformations in solution.

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Section: Resultssupporting

confidence: 88%

Correlating Solution‐ and Solid‐State Structures of Conformationally Flexible Resorcinarenes: Significance of a Sulfonyl Group in Intramolecular Self‐Inclusion

Pamuła

Nissinen

Helttunen

2020

Chemistry A European J

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“…In our previous reports about resorcinarene reactivity [ 19 , 25 ], we found that upper-rim modification proceeds efficiently, and they are independent of the resorcinarene starting material conformation. This result is in agreement with reports of other authors [ 26 ].…”

Section: Introductionsupporting

confidence: 50%

“…Varying the nature of the aldehyde substituent group facilitates the modification at the macrocyclic lower-rim system. At the upper rim, the obvious positions for chemical modification are the resorcinol hydroxyl group and the ortho position [ 18 , 19 , 20 ], the hydroxyl groups of the upper rim being the most common, which can be bridged to form extended cavities or substituted by functional groups for specific applications [ 21 ]. An interesting reagent for resorcinarene modification at the upper rim is glycidyl methacrylate (GMA), which can easily undergo a ring-opening reaction with nucleophilic reagents that contain hydroxyl, carboxyl, trysil or amine groups [ 18 , 22 , 23 ].…”

Section: Introductionmentioning

confidence: 99%

Selective O-Alkylation of the Crown Conformer of Tetra(4-hydroxyphenyl)calix[4]resorcinarene to the Corresponding Tetraalkyl Ether

2017

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Reactions of glycidyl methacrylate with the crown and chair conformers of tetra(4-hydroxyphenyl)calix[4]resorcinarene were studied. The reactions were done over epoxide groups present in the ester, which can easily undergo an opening reaction with hydroxyl groups in the macrocyclic system. Initially, epoxidation reactions were carried out with pure conformers, and it was observed that the reaction between tetra(4-hydroxyphenyl)calix[4]resorcinarene fixed in the chair conformation does not occur, while for the molecule fixed in the crown conformation only one tetraalkylated derivative was obtained. The obtained product was characterized using IR, 1H-NMR, 13C-NMR, COSY, HMQC and HMBC techniques. An exhaustive NMR study showed that the reaction is selective at the hydroxyl groups in the lower rim, without affecting the hydroxyl groups in the upper rim. In addition, the RP–HPLC analysis of the epoxidation reaction mixture, using both crown and chair conformers, showed that only the crown conformer reacted under tested conditions. Finally, a comparative study of the reactivity of tetranonylcalix[4]resorcinarene with glycidyl methacrylate showed that the reaction does not take place. Instead, the formation of the tetranonylcalix[4]resorcinarene tetrasodium salt was observed, which confirms that the hydroxyl groups in the upper rim are unreactive under these conditions.

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“…Continuing with our studies of the structure of polyhydroxylated platforms [12,33,40,41], we found that the bulky aromatic substituents on the lower rim of polyhydroxylated platforms in cone conformation exhibited a dynamic behavior, which stimulated interest in examining the conformational preferences. For this purpose, in this article, the comparative behavior of Ctetra(phenyl)-resorcin [4]arene (1) and C-tetra(phenyl)pyrogallol [4]arene (2) compounds is studied using 1 H-NMR and 13 C-NMR data and dynamic 1 H-NMR spectra.…”

Section: Synthesis and Separation Of Conformersmentioning

confidence: 55%

Experimental Comparative Study of Dynamic Behavior in Solution Phase of C-Tetra(phenyl)resorcin[4]arene and C-Tetra(phenyl)pyrogallol[4]arene

2020

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The synthesis of phenyl-resorcinarenes and pyrogallolarenes is known to produce a conformational mixture of cone and chair isomers. Depending on the synthesis conditions the composition of the conformational mixture is variable; however, the cone conformer is the greatest proportion of phenyl-resorcin[4]arenes and chair conformer of pyrogallol[4]arenes. The experimental evidence suggests that phenyl-substituted resorcinarene and pyrogallolarene exist as a dynamic boat in solution.

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Crystal structure and dynamic NMR studies of octaacetyl-tetra(propyl)calix[4]resorcinarene

Cited by 26 publications

References 38 publications

Correlating Solution‐ and Solid‐State Structures of Conformationally Flexible Resorcinarenes: Significance of a Sulfonyl Group in Intramolecular Self‐Inclusion

Correlating Solution‐ and Solid‐State Structures of Conformationally Flexible Resorcinarenes: Significance of a Sulfonyl Group in Intramolecular Self‐Inclusion

Selective O-Alkylation of the Crown Conformer of Tetra(4-hydroxyphenyl)calix[4]resorcinarene to the Corresponding Tetraalkyl Ether

Experimental Comparative Study of Dynamic Behavior in Solution Phase of C-Tetra(phenyl)resorcin[4]arene and C-Tetra(phenyl)pyrogallol[4]arene

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