The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Nikita Tolstoluzhsky - One of the best experts on this subject based on the ideXlab platform.
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efficient synthesis of uracil derived hexa and tetrahydropyrido 2 3 d pyrimidines
European Journal of Organic Chemistry, 2013Co-Authors: Nikita Tolstoluzhsky, Pavlo Nikolaienko, N N Gorobets, Erik V Van Der Eycken, N N KolosAbstract:A reaction of 6-amino-1,3-dimethyluracil with 3-(hetero)aroylacrylic acids and their methyl esters leads to hexahydropyrido[2,3-d]pyrimidine-5-carboxylic acids or the corresponding methyl esters in high to excellent yields. One-pot oxidation of the acid derivatives with CAN is accompanied by decarboxylation to give tetrahydropyrido[2,3-d]pyrimidines, while oxidation with bromine resulted in the formation of tetrahydropyrido[2,3-d]pyrimidine-5-carboxylic acids. The aromatization of methyl hexahydropyrido[2,3-d]pyrimidine-5-carboxylates was achieved by K2CO3-mediated air oxidation under ambient conditions.
Luca Nardo - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and Spectroscopic Characterization of 2-(het)Aryl Perimidine Derivatives with Enhanced Fluorescence Quantum Yields
Journal of Fluorescence, 2019Co-Authors: Marco Lamperti, Arianna Maria Giani, Angelo Maspero, Guglielmo Vesco, Alessandro Cimino, Roberto Negri, Giovanni Battista Giovenzana, Giovanni Palmisano, Massimo Mella, Luca NardoAbstract:Perimidines are a particularly versatile family of heterocyclic compounds, whose properties are exploited in several applications ranging from industrial to medicinal chemistry. The molecular structure of Perimidine incorporates a well-known efficient fluorophore, i.e.: 1,8-diaminonaphthalene. The high fluorescence quantum yield shared by most naphthalene derivatives, has enabled their use as stains for bio-imaging and biophysical characterizations. However, fluorescence is dramatically depressed in Perimidine as well as in the few of its derivatives analysed so far to this respect. The use of Perimidine-like molecules in life sciences might be notably fostered by enhancement of their fluorescence emission. Even more excitingly, the concomitance of both biologically active moieties and a fluorophore in the same molecular structure virtually discloses application of Perimidines as drug compounds in state-of-art theranostics protocols. However, somewhat surprisingly, relatively few attempts were made until now in the direction of increasing the performances of Perimidines as fluorescent dyes. In this work we present the synthesis and spectroscopic characterization of four Perimidine derivatives designed to this aim, two of which result to be endowed with fluorescence quantum yields comparable to 1,8-diaminonaphthalene. A rationalization for such improved behaviour has been attempted employing TD-DFT calculations, which have unravelled the interrelations among bond structure, lone pair conjugation, local electron density changes and fluorescence quantum yield.
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fluorescence studies on 2 het aryl Perimidine derivatives
Journal of Luminescence, 2016Co-Authors: Arianna Maria Giani, Marco Lamperti, Angelo Maspero, Alessandro Cimino, Roberto Negri, Giovanni Palmisano, Giovanni B Giovenzana, Luca NardoAbstract:Abstract Perimidines are extensively studied for their different therapeutic properties, including antiulcer, antifungal, antimicrobial, immunosuppressive and anticancer activities. Moreover, their heterocyclic structure embodies the naphthalene moiety, exploited in bio-imaging and biomolecules staining due to its high fluorescence. In this work we present the spectroscopic characterization of a family of Perimidine derivatives, in order to obtain information potentially useful for the design of compounds combining biological activity and detectable fluorescence in physiological environment.
Dietmar Keil - One of the best experts on this subject based on the ideXlab platform.
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synthesis and characterization of a new class of unsymmetrical squaraines with 2 3 dihydro 1h Perimidine terminal groups
Dyes and Pigments, 2018Co-Authors: Steffen Ernst, Jurgen Mistol, Bianca Senns, Lothar Hennig, Dietmar KeilAbstract:Abstract Hitherto unknown unsymmetrical squaraines containing 2,3-dihydro-1H-Perimidine terminal groups that are linked through the 4-position and the 6-positions of the 2,3-dihydro-1H-Perimidine terminal groups to the four membered squaraine ring, were obtained as minor products in the reaction of squaric acid with 2,3-dihydro-1H-Perimidines. The structure of these new squaraines was characterized by means of one-dimensional and two-dimensional NMR spectroscopy. The new unsymmetrical squaraines absorb in the NIR region between 777 nm and 781 nm in trichloromethane and between 801 nm and 804 nm in DMSO. This absorption behavior was compared to known symmetrical squaraines of this series, and to previously reported 2,3-dihydro-1H-Perimidine azo dyes. Thus, when compared to symmetrical squaraines in which both 2,3-dihydro-1H-Perimidine terminal groups are linked through their 4-position to the squaraine moiety, the unsymmetrical dyes absorb hypsochromically. Conversely, if the unsymmetrical dyes are compared with symmetrical squaraines that are linked through the 6-position of the 2,3-dihydro-1H-Perimidine ring system, then they absorb at longer wavelengths. Syn-anti isomerization of the unsymmetrical squaraines was investigated by means of 2nd order derivative UV-Vis spectroscopy and NMR spectroscopy, and the results compared with those obtained from the known symmetrical squaraine isomers. These studies indicated that squaraines, in which the 2,3-dihydro-1H-Perimidine terminal groups are linked at their 4-positions, exist to a much greater degree in the anti form due to the presence of hydrogen bonding, whereas a far greater degree of syn-anti isomerism occurs in the other two isomers.
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structural studies of squaraines containing 2 3 dihydro 1h Perimidine terminal groups
Dyes and Pigments, 2015Co-Authors: Jurgen Mistol, Steffen Ernst, Dietmar Keil, Lothar HennigAbstract:Abstract Squaraines containing 2,3-dihydro-1 H -Perimidine terminal groups have been known since 1993. In the literature two structure types have been described; those involving bonding of the four-membered ring to C-4 and those involving bonding to C-6 of the dihydroPerimidine unit. It was found by extensive application of one dimensional and two-dimensional nuclear magnetic resonance spectroscopic techniques, that the 2,3-dihydro-1 H -Perimidine terminal groups are linked at their 4-position with the four-membered cyclic ring, and not at their 6-position. It was also found by nuclear magnetic resonance spectroscopy that hindered rotation about the partial double bond between the 2,3-dihydro-1 H -Perimidine terminal groups and the central four membered cyclic ring, leads to a syn - anti isomerization of the dihydroPerimidine derived squaraine dyes. This feature is confirmed by the detection of two isomers using 2nd order derivative ultraviolet–visible absorption spectroscopy.
Lothar Hennig - One of the best experts on this subject based on the ideXlab platform.
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synthesis and characterization of a new class of unsymmetrical squaraines with 2 3 dihydro 1h Perimidine terminal groups
Dyes and Pigments, 2018Co-Authors: Steffen Ernst, Jurgen Mistol, Bianca Senns, Lothar Hennig, Dietmar KeilAbstract:Abstract Hitherto unknown unsymmetrical squaraines containing 2,3-dihydro-1H-Perimidine terminal groups that are linked through the 4-position and the 6-positions of the 2,3-dihydro-1H-Perimidine terminal groups to the four membered squaraine ring, were obtained as minor products in the reaction of squaric acid with 2,3-dihydro-1H-Perimidines. The structure of these new squaraines was characterized by means of one-dimensional and two-dimensional NMR spectroscopy. The new unsymmetrical squaraines absorb in the NIR region between 777 nm and 781 nm in trichloromethane and between 801 nm and 804 nm in DMSO. This absorption behavior was compared to known symmetrical squaraines of this series, and to previously reported 2,3-dihydro-1H-Perimidine azo dyes. Thus, when compared to symmetrical squaraines in which both 2,3-dihydro-1H-Perimidine terminal groups are linked through their 4-position to the squaraine moiety, the unsymmetrical dyes absorb hypsochromically. Conversely, if the unsymmetrical dyes are compared with symmetrical squaraines that are linked through the 6-position of the 2,3-dihydro-1H-Perimidine ring system, then they absorb at longer wavelengths. Syn-anti isomerization of the unsymmetrical squaraines was investigated by means of 2nd order derivative UV-Vis spectroscopy and NMR spectroscopy, and the results compared with those obtained from the known symmetrical squaraine isomers. These studies indicated that squaraines, in which the 2,3-dihydro-1H-Perimidine terminal groups are linked at their 4-positions, exist to a much greater degree in the anti form due to the presence of hydrogen bonding, whereas a far greater degree of syn-anti isomerism occurs in the other two isomers.
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structural studies of squaraines containing 2 3 dihydro 1h Perimidine terminal groups
Dyes and Pigments, 2015Co-Authors: Jurgen Mistol, Steffen Ernst, Dietmar Keil, Lothar HennigAbstract:Abstract Squaraines containing 2,3-dihydro-1 H -Perimidine terminal groups have been known since 1993. In the literature two structure types have been described; those involving bonding of the four-membered ring to C-4 and those involving bonding to C-6 of the dihydroPerimidine unit. It was found by extensive application of one dimensional and two-dimensional nuclear magnetic resonance spectroscopic techniques, that the 2,3-dihydro-1 H -Perimidine terminal groups are linked at their 4-position with the four-membered cyclic ring, and not at their 6-position. It was also found by nuclear magnetic resonance spectroscopy that hindered rotation about the partial double bond between the 2,3-dihydro-1 H -Perimidine terminal groups and the central four membered cyclic ring, leads to a syn - anti isomerization of the dihydroPerimidine derived squaraine dyes. This feature is confirmed by the detection of two isomers using 2nd order derivative ultraviolet–visible absorption spectroscopy.
Dingyah Yang - One of the best experts on this subject based on the ideXlab platform.
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visible light sensitive properties of 1 2 dimethyl 2 2 nitrophenyl 2 3 dihydro 1h Perimidine
Tetrahedron, 2013Co-Authors: Weizhe Chen, Dingyah YangAbstract:Four o- and p-nitro substituted 2-methyl-2-phenyl-2,3-dihydro-1H-Perimidine derivatives were synthesized via a condensation–cyclization of naphthalene-1,8-diamine with nitro substituted acetophenones to study their photochemical properties. Only the o-nitrophenyl substituted Perimidine 1 was found to be sensitive to light. When exposed to visible light under either aerobic conditions or argon atmosphere, it undergoes pyrimidine ring-opening/deoxygenation and pyrimidine oxidation to give the 2H-indazole 10 and perimidinone 11, respectively. A new visible light-sensitive o-nitrobenzylamino scaffold is introduced.
