Showing papers on "Fluorene published in 1980"
47 citations
29 citations
TL;DR: The results obtained with denatured DNA in the absence and the presence of chemical modifications by AAAF or AAAIF allow us to conclude that energy transfer contributes to fluorescence quenching in the case of AAIF but not in that of AAF.
Abstract: The binding of the tripeptide Lys-Trp-Lys to DNA modified by reaction with the chemical carcinogen 2-(N-acetoxyacetylamino)fluorene (AAAF) has been investigated by fluorescence spectroscopy. A quenching of tryptophan fluorescence was observed which increased when the degree of base substitution by AAAF increased. Similar results were obtained with the 7-iodo derivative of AAAF (AAAIF). Two hypotheses are discussed which could account for the experimental results: (1) stacking interactions of the tryptophyl residue of the peptide with nucleic acid bases in locally unpaired regions in the vicinity of modified bases; (2) energy transfer from the tryptophyl residue of the peptide to acetylaminofluorene bound to guanine bases without direct interaction of this residue with nucleic acid bases (outside binding). The results obtained with denatured DNA in the absence and the presence of chemical modifications by AAAF or AAAIF allow us to conclude that energy transfer contributes to fluorescence quenching in the case of AAIF but not in that of AAF. Stacking interactions are therefore responsible for fluorescence quenching of Lys-Trp-Lys when bound to AAF-modified DNA. In the case of DNA-AAIF, fluorescence quenching is due both to energy transfer and to stacking of the tryptophan ring with bases inside the helix. These results are discussed in relation to what is already known in terms of local structure and with respect to the role that could be played by aromatic residues of proteins in the recognition of chemically damaged DNA.
16 citations
TL;DR: N-Benzoylimidazole in trifluoroacetic acid could benzoylate electron-rich aromatic compounds, such as durene, p-dimethoxybenzene, mesitylene, anisole, thiophene, and fluorene, to give the correspon...
Abstract: N-Benzoylimidazole in trifluoroacetic acid could benzoylate electron-rich aromatic compounds, such as durene, p-dimethoxybenzene, mesitylene, anisole, thiophene, and fluorene, to give the correspon...
13 citations
TL;DR: In this article, the rotamers of 9-(2-hydroxy-1-naphthyl)fluorene, 9-( 2-hydroxyl 4,6-dimethylphenyl) fluororene and their methyl ethers have been prepared.
Abstract: 9-(2-Hydroxy-1-naphthyl)fluorene, 9-(2-hydroxy-4,6-dimethylphenyl)fluorene, and their methyl ethers have been prepared. They give stable rotamers, sp and ap, at room temperature, ap forms of the hy...
12 citations
TL;DR: In this paper, the Eu(fod) 3 shift reagent induces shifts in the same sequence, H(1) (closest to carbonyl), H(4) ⪢ H(3) ⫡ H(2), as when the solvent is changed from carbon disulphide to chloroform, and a planar geometry for I is favored.
11 citations
TL;DR: In this article, it was shown that the major process was electron transfer followed by proton transfer, followed by a radical reaction also participated as a minor process, and a possible reaction mechanism similar to the photo-induced Birch reduction was proposed.
Abstract: Irradiation of fluoren-9-ol and its acetate in the presence of an aliphatic amine gave fluorene as the major product. The yield of fluorene depended upon the character of amine and increased in the order of primary < secondary < tertiary amines. By the use of deuteriated reagents ([2H1]methanol and [2H3]acetonitrile) it was revealed that the major process was electron transfer followed by proton transfer. A radical reaction also participated as a minor process. A possible reaction mechanism similar to the photo-induced Birch reduction was proposed.
9 citations
TL;DR: In this paper, the carbon-13 NMR spectra of polyaromatic transition metal complexes and their isomeric mixtures containing species of the same or different structural types are described by the fingerprint method, 13C spin-lattice relaxation time measurements, and an additive calculation of carbon chemical shifts of the methyl-substituted complexes (II,III).
8 citations
TL;DR: In this paper, a base-catalyzed autoxidation of fluorene to fluorenone has been carried out in an aqueous potassium hydroxide-benzene two-phase system in the presence of 18-crown-6 as a phase transfer catalyst.
Abstract: Base-catalyzed autoxidation of fluorene to fluorenone has been carried out in an aqueous potassium hydroxide–benzene two-phase system in the presence of 18-crown-6 as a phase transfer catalyst. The initial rate of oxidation is proportional to the amount of fluorene. The addition of 18-crown-6 leads to the increased concentration of potassium hydroxide and water in the benzene phase, which is responsible for the increased rate of oxidation. Increasing the concentration of potassium hydroxide in the aqueous phase increases the concentration of 18-crown-6 and potassium hydroxide in benzene, resulting in a large increase in the rate of oxidation. The ease of oxidation with respect to the base is KOH>NaOH>LiOH>Ba(OH)2. Less polar solvents such as cyclohexane used as an organic phase decrease the oxidation rate.
8 citations
Abstract: Triarylmethanols containing one or more fluorine substituents in the para-positions are converted by 90% formic acid into a mixture of the fluorine-containing triarylmethane, and a second component in which one fluorine has been replaced by a hydroxy-group. A mechanism is proposed which involves nucleophilic attack by water on the initial carbonium ion (4) with subsequent loss of hydrogen fluoride, to give the diphenyl-p-hydroxyphenylmethyl carbonium ion (6) which undergoes hydride transfer with formate to give the product. This mechanism was supported by the isolation of 4-hydroxytriphenylmethanol from the reaction involving 4-fluorotriphenylmethanol. Pentafluorophenyldiphenylmethanol on similar treatment gave 9-(pentafluorophenyl)fluorene, and 2-(trifluoromethyl)triphenylmethanol gave 9-(2-trifluoromethylphenyl)fluorene. Both reactions presumably occur via an intramolecular electrophilic aromatic substitution. The 19F and 13C n.m.r. spectra of the triarylmethanes and 9-arylfluorenes are reported and discussed.
6 citations
TL;DR: The synthesis of five novel electrono-donor monomers containing fluorene and of the corresponding polymers is described.
Abstract: The synthesis of five novel electrono-donor monomers containing fluorene (2-fluorenyl acrylamide, 2-fluorenyl methacrylamide, 2-(1-hydroxyethyl)fluorenyl acrylate, 2-(1-hydroxyethyl)fluorenyl methacrylate and 9-fluorenyl acrylate) and of the corresponding polymers is described.
TL;DR: In this paper, it was shown that potassium superoxide can initiale autoxidations of fluorene, diphenylmethane, and distyryl methane.
Abstract: Potassium superoxide was found to initiale autoxidations of fluorene, diphenylmethane, and distyrylmethane. In each case the oxidation results in the formation of ketones as primary products. Kinet...
TL;DR: In this paper, LiSiMe 3 ) 6 (I) reacts with tetramethylethylenediamine (TMEDA) to yield the crystalline product (LiSiMe3 ) 2 · (TM EDA) 3 (II).
TL;DR: In this article, the reactions of arenesulphonyl azides with 2,3-dihydro-1H-pyrrolo[1,2-a]indole, with 1,2,2a,3,4,5,hyxahydropyryrrolos[3, 2,2.1]-carbazole, and with 1.2,4-5-tetrahydroid-2a-methyl-3-oxa-10-azacyclopenta[jk]flu
Abstract: The reactions of arenesulphonyl azides with 2,3-dihydro-1H-pyrrolo[1,2-a]indole, with 2,3-dihydro-9-methyl-1H-pyrrolo[1,2-a]indole, with 1,2,2a,3,4,5-hyxahydropyrrolo[3,2,1-jk]carbazole, and with 1,2,4,5-tetrahydro-2a-methyl-3-oxa-10-azacyclopenta[jk]fluorene in various solvents have been investigated and structures assigned to the reaction products.
TL;DR: In this article, the formation of solvation complex of poly(ethylene oxide), polydimethoxyethylene, and polydioxene with some alkali derivatives of fluorene in dioxane was found, differing in the ionic species of the fluorenyl metal in the complex.
Abstract: The formation of two kinds of solvation complex of poly(ethylene oxide), polydimethoxyethylene, and polydioxene with some alkali derivatives of fluorene in dioxane was found, differing in the ionic species of the fluorenyl metal in the complex. Additional evidence was found for the existence of peripherally solvated ion pairs of fluorenyllithium, -sodium, and -potassium. It was shown that polydimethoxyethylene and polydioxane interact with different cations in a different manner. The complexing ability of poly(ethylene oxide) and polydioxane with respect to fluorenyllithium, -sodium, and -potassium, and of polydimethoxyethylene for fluorenyllithium, was proved to be stronger than that of their monomer analogs—dimethoxyethane and dioxane. This was explained by the effect of the polymer chain.
TL;DR: In this article, the reaction of newly obtained aminophosphonic acid diethyl ester derivatives of fluorene with Cr2O72−, CrO42− and CrO3Cl− has been investigated using electronic, infrared, Ramaman and NMR spectral methods.
Abstract: The studies on reaction of newly obtained aminophosphonic acid diethyl ester derivatives of fluorene with Cr2O72−, CrO42−, CrO3Cl− and CrO3 have been investigated using electronic, infrared,Raman and NMR spectral methods. It has been found that the resulting compounds are of the type (AH)2Cr2O7, whereA stands for the organic part of the molecule. The organic cation and solvent effects on the electronic states of pseudotetrahedrally arranged Cr(VI) anions are discussed.
TL;DR: In this article, the authors investigated the triplet state radical pair in fluorene single crystals doped with anthracene and showed that the resulting three-state radical pair can be investigated by EPR.
Abstract: Light absorption in fluorene single crystals doped with anthracene induces a photoreaction. One hydrogen atom from a fluorene host gets transferred to an anthracene guest molecule over a distance of several angstroms. The resulting triplet state radical pair is investigated by EPR. Fine‐ and hyperfine structure analyses are given. The photoprocess is similar to that found earlier in fluorene crystals doped with acridine or phenazine. Where the nitrogen lone pair orbitals of acridine or phenazine were suitable acceptors for the transferred hydrogen atoms with anthracene, the hydrogen has to enter a tetrahedral sp3 configuration at the guest molecule. Somewhat higher crystal temperatures are required for comparable intensity EPR‐lines of the photoproduct.
TL;DR: The Bronsted leaving group plot for the alkaline hydrolysis of fluorene-9-carboxylate esters in the pH region corresponding to the existence of the ester anion is shown in this article.
Abstract: The Bronsted leaving group (β1g) plot for the alkaline hydrolysis of fluorene-9-carboxylate esters in the pH region corresponding to the existence of the ester anion shows a minimum flanked by a region of high negative β1g(-1·01), corresponding to an E1cb pathway and, for esters of pK1g > 9·5, a region of positive β1g(+0·11).
Journal Article•
TL;DR: An increase in the length of the Sn-C (fluorene) bond is not observed in crystals of 9-fluorenyl derivatives of tin, and the variation in the lengths of Sn-Me bonds is similar to that found in other types of organotin compounds as discussed by the authors.
Abstract: An increase in the length of the Sn-C (fluorene) bond is not observed in crystals of 9-fluorenyl derivatives of tin, and the variation in the lengths of the Sn-Me bonds is similar to that found in other types of organotin compounds.
TL;DR: N-Benzoylimidazole in trifluoroacetic acid could benzoylate electron-rich aromatic compounds, such as durene, p-dimethoxybenzene, mesitylene, anisole, thiophene, and fluorene, to give the correspon...
Abstract: N-Benzoylimidazole in trifluoroacetic acid could benzoylate electron-rich aromatic compounds, such as durene, p-dimethoxybenzene, mesitylene, anisole, thiophene, and fluorene, to give the correspon...