Enaminone Substituted Resorcin[4]arene—Sealing of an Upper-Rim with a Directional System of Hydrogen-Bonds

Szafraniec, Anna; Grajda, Marcin; Jędrzejewska, Hanna; Szumna, Agnieszka; Iwanek, Waldemar

doi:10.3390/ijms21207494

Cited by 3 publications

(1 citation statement)

References 36 publications

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“…While this definition requires a cyclic arrangement of stereocenters, the concept of “cyclostereoisomerism” was expanded by Mislow , to cover other aspects of isomerism that arise when cyclic arrangements of stereocenters are associated with ring systems. Since 2007, the term “cyclochirality” has been used in various contexts to describe the (often dynamic) chirality that arises in cyclic arrays where repulsive interactions such as steric hindrance , or attractive interactions such as hydrogen bonds − govern the coherent formation of alternative isomeric structures. In a few examples, contiguously hydrogen-bonded networks control the cyclochirality of the structure.…”

Section: Introductionmentioning

confidence: 99%

Dynamic and Persistent Cyclochirality in Hydrogen-Bonded Derivatives of Medium-Ring Triamines

Morris,

Wales,

Echavarren

et al. 2023

J. Am. Chem. Soc.

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Cyclic triureas derived from 1,4,7-triazacyclononane (TACN) were synthesized; X-ray crystallography showed a chiral bowl-like conformation with each urea hydrogen-bonded to its neighbor with uniform directionality, forming a "cyclochiral" closed loop of hydrogen bonds. Variable-temperature 1 H NMR, 1 H-1 H exchange spectroscopy, Eyring analysis, computational modeling, and studies in various solvents revealed that cyclochirality is dynamic (ΔG ‡ 25°C = 63−71 kJ mol −1 in noncoordinating solvents), exchanging between enantiomers by two mechanisms: bowl inversion and directionality reversal, with the former subject to a slightly smaller enantiomerization barrier. The enantiomerization rate substantially increased in the presence of hydrogen-bonding solvents. Population of only one of the two cyclochiral hydrogen-bond directionalities could be induced by annulating one ethylene bridge with a trans-cyclohexane. Alternatively, enantiomerization could be inhibited by annulating one ethylene bridge with a cis-cyclohexane (preventing bowl inversion) and replacing one urea function with a formamide (preventing directionality reversal). Combining these structural modifications resulted in an enantiomerization barrier of ΔG ‡ 25°C = 93 kJ mol −1 , furnishing a planar-chiral, atropisomeric bowlshaped structure whose stereochemical stability arises solely from its hydrogen-bonding network.

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Section: Introductionmentioning

confidence: 99%

Dynamic and Persistent Cyclochirality in Hydrogen-Bonded Derivatives of Medium-Ring Triamines

Morris,

Wales,

Echavarren

et al. 2023

J. Am. Chem. Soc.

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Theoretical calculations of formation and reactivity of o -quinomethide derivatives of resorcin[4]arene with reference to empirical data

Iwanek

2022

R. Soc. open sci.

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This paper describes theoretical reaction pathways of alkoxybenzyl derivatives of resorcin[4]arene leading to the formation of o -quinomethide derivatives of resorcin[4]arene ( o- QMR[4]A). For each case, the activation energies for the formation of one o -QMR[4]A unit and the activation energies for the backward reaction were calculated. Based on the calculated reaction pathways, the reaction mechanism of o -QMR[4]A formation was proposed. Using the example of o -QMR[4]A generated from a methoxy derivative of resorcin[4]arene, the activation energies with selected nucleophiles were calculated and the reaction mechanisms discussed. Reaction path calculations were performed using the nudged elastic band method and semiempirical extended tight-binding method (GFN2-xTB). Using hydroxybenzyl derivatives of resorcin[4]arene as an example, a comparison of calculated activation energies by selected density-functional theory methods with GFN2-xTB and B97-3c geometries was performed. B97-3c and wB97XD methods were used to calculate the energies of the reactants (R), transition states (TS) and products (P) of the analysed reactions. Theoretical reaction mechanisms were discussed with respect to the orbital-weighted Fukui dual descriptor (Δ f w ) and experimental data.

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Diverse Applications of β-enaminone Ligands and their Metal Complexes: A Review ‎Article

Faisal,

Waheed,

Ahmed

2023

Al-Kitab J. Pure Sci.

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As they include both nucleophilic and electrophilic moieties on the same skeleton, enaminones are an important subclass of chemical compounds that contain conjugated NC=C-C=O fragments. These active sites aid in the production of organic molecules containing linear or cyclic heteroatoms. Enaminones and the chemica1 compounds produced from them are both biologically active against the most dangerous bacteria. As a result, they have been utilized as starting materials for the synthesis of anti-inf1ammatory, antibacteria1, anticonvulsant, anticancer, anti-urease, anti-malaria1, optically luminescent, corrosion inhibition, and antitumor agents. Their synthesis has usually a terrific deal of interest and a plethora of synthetic paths have been narrated, including Lewis’s acids, P2O5/SiO2, Cu- nanoparticles, and heteropoly acid. Enaminone metal complexes have serval applications in industry and engineering. ‎The definition, significance, and diverse applications of β-enaminone 1igands and their ‎meta1 complexes are presented in this review study.

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Enaminone Substituted Resorcin[4]arene—Sealing of an Upper-Rim with a Directional System of Hydrogen-Bonds

Cited by 3 publications

References 36 publications

Dynamic and Persistent Cyclochirality in Hydrogen-Bonded Derivatives of Medium-Ring Triamines

Dynamic and Persistent Cyclochirality in Hydrogen-Bonded Derivatives of Medium-Ring Triamines

Theoretical calculations of formation and reactivity of o -quinomethide derivatives of resorcin[4]arene with reference to empirical data

Diverse Applications of β-enaminone Ligands and their Metal Complexes: A Review ‎Article

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