Coumarin[4]arene: A Fluorescent Macrocycle

Kumar, Pawan; Venkatakrishnan, Parthasarathy

doi:10.1021/acs.orglett.7b04045

Cited by 35 publications

(17 citation statements)

References 48 publications

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“…Previously, self‐inclusion dimers of resorcinarene tetrapodands have been observed by us and others . Nevertheless, resorcinarene podands tend to display collapsed cavities in the solid state …”

Section: Introductionmentioning

confidence: 74%

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: Introductionmentioning

confidence: 74%

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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“…However, linear coumarins, beyond benzo[ g ]coumarins, have not been achieved so far and their optical properties remain yet unexplored. In continuation to our recent efforts on coumarin and its π‐expansion, [ 8c,10,11 ] to build on its chemistry further we have herein targeted the synthesis of novel coumarinacenes (Scheme 1). Coumarinacenes are linearly π‐expanded coumarin analogues.…”

Section: Methodsmentioning

confidence: 99%

Linear Coumarinacenes Beyond Benzo[g]coumarins: Synthesis and Promising Characteristics

et al. 2020

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New heteroacenes, named coumarinacenes, have been designed, synthesized and characterized. They possess visible absorption and orange-red emission that are far beyond those of benzo[g]coumarins. They exhibit deep HOMO energy levels, and reveal excellent thermal, photochemical and air sta-Coumarins are pyranone-annulated benzenes (2H-benzopyran-2-ones) that are ubiquitous in nature. [1] They are actually popular for their wide spectrum of biological and pharmacological activities, [2a] such as, antioxidant, [2b] antidepressant, [2c] anticoagulant, [2d] anti-inflammatory, [2e] antifungal, [2f ] antitumor, [2g] anti-HIV, [2h] antibiotic, [2i] etc., and for their excellent biocompatibility. [1] Structurally simple derivatives of coumarin exhibit rich photophysical and photochemical properties (high photoluminescence quantum yields, large Stokes shifts and good photostability) paving their entry into modern photonic applications; laser dyes, [3a,3b] non-linear optics, [3c] two-photon bioimaging [3d] and sensing [3e] are some examples. Moreover, coumarin derivatives are recently being exploited as functional materials in organic light emitting devices, [4a,4b] liquid crystals, [4c] dye-sensitized solar cells, [4d,4e] electron and energy transfer systems, [4f,4g] and fluorescent probes. [4h] Despite the broad utility of coumarins, the low-lying absorption and emission wavelengths (due to shorter conjugation lengths) are primarily the bottlenecks in furthering their applications. In an effort to overcome the limitations, considerable attention is devoted in recent times for the development of novel π-expanded coumarin dyes. [5] Benzocoumarins-the simplest π-expanded benzene-fused coumarins-indeed absorb and emit light in the longer wavelength region when compared to parent coumarins (Scheme 1). [6] Among the other isomeric [a] A

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“…47 The P 2 O 5 –MeSO 3 H combination is known as Eaton’s reagent, 48 which is an alternative reagent to polyphosphoric acid (PPA) for the promotion of (cyclo)dehydration reactions. 49–54 Herein, we have applied Eaton’s reagent to mediate the synthesis of 3-substituted or 2,3-disubstituted benzofurans efficiently under mild conditions.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of benzofurans from the cyclodehydration of α-phenoxy ketones mediated by Eaton’s reagent

Zhou

et al. 2020

Journal of Chemical Research

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Cyclodehydration of α-phenoxy ketones promoted by Eaton’s reagent (phosphorus pentoxide–methanesulfonic acid) is used to prepare 3-substituted or 2,3-disubstituted benzofurans with moderate to excellent yields under mild conditions. The method provides a facile access to benzofurans from readily available starting materials such as phenols and α-bromo ketones. The reaction is highly efficient, which is attributed to the good reactivity and fluidity of Eaton’s reagent. The reaction can be applied to prepare naphthofurans, furanocoumarins, benzothiophenes, and benzopyrans.

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Coumarin[4]arene: A Fluorescent Macrocycle

Abstract: The pyranone functionalization of the upper rim of resorcinarene to provide the coumarin macrocycle called "coumarin[4]arene", possessing visible fluorescence and conformationally flexible behavior suitable for molecular recognition, has been successfully synthesized and characterized.

Cited by 35 publications

References 48 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

Linear Coumarinacenes Beyond Benzo[g]coumarins: Synthesis and Promising Characteristics

Synthesis of benzofurans from the cyclodehydration of α-phenoxy ketones mediated by Eaton’s reagent

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