Stable Simple Enols. Self-CatalyzedE/Z-Isomerization of the Sterically Crowded 2-(m-Methoxymesityl)-1,2-dimesitylethenol1

Rochlin, Elimelech; Rappoport, Zvi

doi:10.1021/jo020665e

Cited by 13 publications

(14 citation statements)

References 29 publications

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“…Similarly, the rate constants of the folding of 3 increased threefold with an increase in concentration from (4.9±0.1)×10 −3 (1 μ m) , to (1.7±0.1)×10 −2 min −1 (7 μ M ) (Figure 15 b). 23 These phenomena were attributed to self‐catalysis, as reported for apparent first‐order reactions such as the epimerization of chlorophyll [25] and the isomerization of aldose26 or enol 27…”

Section: Resultsmentioning

confidence: 97%

Reversible Double‐Helix–Random‐Coil Transition Process of Bis{hexa(ethynylhelicene)}s

Sugiura

Amemiya

Yamaguchi

2008

Chemistry An Asian Journal

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Two compounds with two hexa(ethynylhelicene) parts connected by a flexible hexadecamethylene and a rigid butadiyne linker were synthesized. The 1H NMR spectroscopic and CD analyses and vapor-pressure osmometry (VPO) of these two compounds revealed intramolecular double-helix formation. Upon heating a 5-microM solution in toluene, the double-helix structure unfolded to form a random coil, and on cooling it folded again into a double helix. The thermodynamic stabilities of both structures were dependent on temperature, and the structural change in both compounds is due to the large enthalpies and entropies under equilibrium. The rate constants of their unfolding were obtained by assuming a pseudo-first-order reaction; the compound with a rigid linker unfolded slower than that with a flexible linker. The former has a larger activation energy, and its double-helix and random-coil conformers were separated by chromatography. The rate of folding was also faster for the flexible-linker compound with larger activation energy. The rate constants for the folding of both compounds slightly decreased with increasing temperature, which was ascribed to the presence of exothermic pre-equilibrium and rate-determining steps. The folding was markedly accelerated with increasing random-coil concentration, which suggests the involvement of self-catalysis. A mechanism of folding was proposed. The involvement of different mechanisms of folding and unfolding was suggested by the kinetic studies, and it was confirmed by the presence of hysteresis in the melting profiles. The difference in linker structure also affected the thermal-switching profiles of the double-helix-random-coil structural changes.

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Section: Resultsmentioning

confidence: 97%

Reversible Double‐Helix–Random‐Coil Transition Process of Bis{hexa(ethynylhelicene)}s

Sugiura

Amemiya

Yamaguchi

2008

Chemistry An Asian Journal

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“…9,10-Anthraquinone-1-diazonium tetrafluoroborate (AQD) was prepared from 1-aminoanthraquinone (Sigma-Aldrich) according to published procedures [52][53][54]. Briefly, 1-aminoanthraquinone (500 mg; 2.2 mmol) was dissolved in acetone (5 mL) while stirring.…”

Section: Chemical Reagentsmentioning

confidence: 99%

Electrochemical Behaviour of HOPG and CVD‐Grown Graphene Electrodes Modified with Thick Anthraquinone Films by Diazonium Reduction

et al. 2014

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Highly oriented pyrolytic graphite (HOPG) and graphene grown on Ni (Ni‐Gra) or Cu (Cu‐Gra) by chemical vapour deposition were modified with thick anthraquinone (AQ) films (7−60 nm) by redox grafting of the pertinent diazonium salt. Glassy carbon (GC) electrodes were used for comparison. The AQ‐modified GC electrodes showed excellent blocking properties towards the Fe(CN)63−/4− redox probe, although it was noted that in the case of Ni‐Gra and Cu‐Gra, the blocking ability depended strongly on the underlying substrate. Oxygen reduction studies revealed good electrocatalytic activity of AQ‐modified HOPG, Ni‐Gra, and Cu‐Gra, compared with the bare electrodes.

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“…The synthesis of anthrols 2−5 started from the commercially available 2-aminoanthraquinone, which was converted to 2-hydroxyanthraquinone (8) via a known procedure. 38 Bromination of 8 with excess of bromine afforded a mixture of 3-bromo-2-hydroxyanthraquinone (9) and 1,3dibromo-2-hydroxyanthraquinone (10). The mixture was subjected to a reduction with NaBH 4 in alkaline aqueous solution (1 M Na 2 CO 3 ) to yield pure 2-bromo-3-anthrol (11).…”

Section: ■ Resultsmentioning

confidence: 99%

Photochemical Formation of Anthracene Quinone Methide Derivatives

Škalamera¹,

Mlinarić‐Majerski²,

Kleiner³

et al. 2017

J. Org. Chem.

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Anthrols 2-7 were synthesized and their photochemical reactivity investigated by irradiations in aq CHOH. Upon excitation with visible light (λ > 400 nm) in methanolic solutions, they undergo photodehydration or photodeamination and deliver methyl ethers, most probably via quinone methides (QMs), with methanolysis quantum efficiencies Φ = 0.02-0.3. Photophysical properties of 2-7 were determined by steady-state fluorescence and time-correlated single photon counting. Generally, anthrols 2-7 are highly fluorescent in aprotic solvents (Φ = 0.5-0.9), whereas in aqueous solutions the fluorescence is quenched due to excited-state proton transfer (ESPT) to solvent. The exception is amine 4 that undergoes excited-state intramolecular proton transfer (ESIPT) in neat CHCN where photodeamination is probably coupled to ESIPT. Photodehydration may take place via ESIPT (or ESPT) that is coupled to dehydration or via a hitherto undisclosed pathway that involves photoionization and deprotonation of radical cation, followed by homolytic cleavage of the alcohol OH group from the phenoxyl radical. QMs were detected by laser flash photolysis and their reactivity with nucleophiles investigated. Biological investigation of 2-5 on human cancer cell lines showed enhancement of antiproliferative effect upon exposure of cells to irradiation by visible light, probably due to formation of electrophilic species such as QMs.

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Stable Simple Enols. Self-CatalyzedE/Z-Isomerization of the Sterically Crowded 2-(m-Methoxymesityl)-1,2-dimesitylethenol¹

Cited by 13 publications

References 29 publications

Reversible Double‐Helix–Random‐Coil Transition Process of Bis{hexa(ethynylhelicene)}s

Reversible Double‐Helix–Random‐Coil Transition Process of Bis{hexa(ethynylhelicene)}s

Electrochemical Behaviour of HOPG and CVD‐Grown Graphene Electrodes Modified with Thick Anthraquinone Films by Diazonium Reduction

Photochemical Formation of Anthracene Quinone Methide Derivatives

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