- IR SPECTRA AND PHOTOTAUTOMERISM OF MATRIX ISOLATED 4-OXOPYRIMIDINE
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Uv-light induced intramolecular proton-transfer was observed in matrix isolated 4-oxopyrimidine, 2-pyridone and hypoxanthine.Mixed spectrum of 4-oxo- and 4-hydroxy-pyrimidine in Ar and Ne matrices was unambiguously partitioned into the two sets of peaks corresponding to the two tautomers.Both spectra were compared to the spectra in the solid phases and interpreted.
- Nowak, M. J.,Fulara, J.,Lapinski, L.
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- Ab initio calculations of IR spectra in identification of products of matrix isolation photochemistry. Dewar form of 4(3H)-pyrimidinone
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Ab initio calculations of the infrared spectrum of the Dewar isomer of 3-methyl-4(3H)-pyrimidinone have been carried out at the MP2/6-31G and SCF/6-31G levels of theory. These were compared with the experimental spectrum of the photoproduct that emerged upon UV (308 nm) irradiation of 3-methyl-4(3H)-pyrimidinone isolated in a low-temperature argon matrix. The agreement between the spectrum simulated at the MP2 level and the experimental spectrum was remarkable and enabled positive assignment of the photoproduct structure. Photoreactions of matrix-isolated 4(3H)-pyrimidinones not methylated at the N3 nitrogen atom have also been studied. For these compounds, three types of photoreactions were observed, i.e., phototautomerism, ring opening, and Dewar structure formation. The relative probabilities of the three competing reaction directions and their dependencies on ring substitutions have been investigated, and results are presented.
- Lapinski,Nowak,Les,Adamowicz
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- Thermal Behavior Analysis of Two Synthesized Flavor Precursors of N-alkylpyrrole Derivatives
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To expand the library of pyrrole-containing flavor precursors, two new flavor precursors—methyl N-benzyl-2-methyl-5-formylpyrrole-3-carboxylate (NBMF) and methyl N-butyl-2-methyl-5-formylpyrrole-3-carboxylate (NUMF)—were synthesized by cyclization, oxidation, and alkylation reactions. Thermogravimetry (TG), differential scanning calorimeter, and pyrolysis–gas chromatography/mass spectrometry were utilized to analyze the thermal degradation behavior and thermal degradation products of NBMF and NUMF. The TG-DTG curve indicated that the maximum mass loss rates of NBMF and NUMF appear at 310 and 268°C, respectively. The largest peaks of NBMF and NUMF showed by the differential scanning calorimeter curve were 315 and 274°C, respectively. Pyrolysis–gas chromatography/mass spectrometry detected small molecule fragrance compounds appeared during thermal degradation, such as 2-methylpyrrole, 1-methylpyrrole-2-carboxylic acid methyl ester, limonene, and methyl formate. Finally, the thermal degradation mechanism of NBMF and NUMF was discussed, which provided a theoretical basis for their application in tobacco flavoring additives.
- Ai, Lvye,Liu, Mengzhen,Ji, Xiaoming,Lai, Miao,Zhao, Mingqin,Ren, Tianbao
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p. 2389 - 2397
(2019/08/01)
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- 1N-ALKYL-N-ARYLPYRIMIDINAMINES AND DERIVATIVES THEREOF
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The present invention provides novel compounds, compounds and pharmaceutical compositions thereof, and methods of using same in the treatment of affective disorders, anxiety, depression, post-traumatic stress disorders, eating disorders, supranuclear palsy, irritable bowel syndrome, immune suppression, Alzheimer'disease, gastrointestinal diseases, anorexia nervosa, drug and alcohol withdrawal symptoms, drug addiction, inflammatory disorders, or fertility problems. The novel compounds provided by this invention are those of formula: wherein R 1, R 3, R 4, R 5, Z, Y, V, X, X', J, K, L, and M are as defined herein.
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- 1N-alkyl-N-arylpyrimidinamines and derivatives thereof
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The present invention provides novel compounds, compounds and pharmaceutical compositions thereof, and methods of using same in the treatment of affective disorders, anxiety, depression, post-traumatic stress disorders, eating disorders, supranuclear palsy, irritable bowel syndrome, immune suppression, Alzheimer's disease, gastrointestinal diseases, anorexia nervosa, drug and alcohol withdrawal symptoms, drug addiction, inflammatory disorders, or fertility problems. The novel compounds provided by this invention are those of formula: wherein R1, R3, R4, R5, Z, Y, V, X, X', J, K, L, and M are as defined herein.
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- Combined matrix-isolation FT-IR and ab initio 6-31++G** study of H-bonded complexes between water and molecules modelling cytosine or isocytosine
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A step-by-step experimental and ab initio SCF/6-31++G** procedure is described for the interpretation of the matrix FT-IR spectra of H-bonded complexes of cytosine or isocytosine with water.The method involves a detailed study of several compounds, each modelling one or a few cytosine sites and/or tautomers in order of increasing complexity.Results are presented for tautomerization processes in 2-OH-pyridine, 4-OH-pyrimidine and isocytosine, and for H-bonded complexes of water with pyrimidine, 4-OH-pyridine and 4-NH2-pyridine.The whole series of obtained results has allowed the setting up of a large-scale vibration correlation diagram for water complexed with N- and O-bases.It also allows some new, important conclusions to be drawn about the major problem of scaling ab initio predicted frequencies for anharmonic proton-donor vibrational modes.
- Smets, Johan,Adamovicz, Ludwik,Maes, Guido
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p. 113 - 130
(2007/10/02)
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- Dual Fluorescence of 4-(Dialkylamino)pyrimidines. Twisted Intramolecular Charge Transfer State Formation Favored by Hydrogen Bond or by Coordination to the Metal Ion
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4-(N,N-dimethylamino)pyrimidine (4-DMAP) does not exhibit any markedly dual luminescence even in highly polar (aprotic) solvents, unless the ortho substituent deviates the amino group from coplanarity with the ring.Protic solvents or complexation with Zn2+ cause the long-wave fluorescence to appear distinctly.Contrary to 4-DMAP, 4-(N,N-diethylamino)pyrimidine (4-DEAP) reveals dual luminescence in sufficiently polar (aprotic) environment.In alcoholic solutions the intensity of the fluorescence is drastically reduced.Fluorescence properties of this group of compounds fit well to the TICT modell.The importance of nonradiative deactivation increases with the proton-donating ability of the solvent.
- Herbich, Jerzy,Grabowski, Zbigniew R.,Wojtowicz, Hanna,Golankiewicz, Krzysztof
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p. 3439 - 3444
(2007/10/02)
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- Theoretical Description of Solvent Effects. V. The Medium Influence on the Lactim-Lactam Tautomerism of Hydroxyazines
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Der Loesungsmitteleffekt auf die Tautomeriegleichgewichte der Titelverbindungen wird mit Hilfe klassischer und quantenchemischer Versionen der Solvatonen- und der Reaktionsfeldtheorie berechnet.In Uebereinstimmung mit dem Experiment ergeben alle getesteten Verfahren eine Gleichgewichtsverschiebung zugunsten der Lactamform.Zur quantitativen Beschreibung dieses Effektes ist jedoch das Reaktionsfeldmodell besser geeignet.
- Krebs, C.,Foerster, W.,Weiss, C.,Hofmann, H.-J.
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p. 369 - 378
(2007/10/02)
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- TAUTOMERIC EQUILIBRIA OF 2(4)-MONOOXOPYRIMIDINES IN THE GAS PHASE, IN LOW-TEMPERATURE MATRICES AND IN SOLUTION
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IR absorption spectra, including the NH, OH and C=O stretching regions, have been recorded for 4-oxo-6-methyl- and 2-oxo-4,6-dimethyl pyrimidines and several related derivatives, in the gas phase, in low-temperature inert matrices, and in several liquid solvents.All the 4-oxopyrimidines in the gas phase, and 4-oxo-6-methylpyrimidine in low-temperature matrices, exhibit comparable populations of the keto and enol forms.By contrast the 2-oxopyrimidines are predominantly in the enol forms.Both classes of compounds are predominantly in the keto form in liquid solvent systems.The tautomeric equilibrium constant (KT) in the vapour phase for 4-oxo-2,6-dimethylpyrimidine is about 2, and for the other 4-oxopyrimidines is about 1.For 4-oxo-6-methylpyrimidine, the equilibrium constant in inert matrices varies slightly with the activity of the matrix gas, with the keto tautomer favoured in the more active matrix.From the temperature-dependence of KT, the free energy difference between the two tautomeric forms of 4-oxo-6-methylpyrimidine in the vapour phase has been calculated.Heats of vaporization have also been calculated for the various compounds and related to their abilities to associate by hydrogen bonding in the condensed phase.The UV absorption spectra of some of the foregoing have also been recorded in the gas phase, but these were of only limited value in studies of tautomeric equilibria, as compared to the IR spectra.
- Nowak, M. J.,Szczepaniak, K.,Barski, A.,Shugar, D.
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- EQUILIBRE LACTIME-LACTAME DES HYDROXY-PYRIDINES ET DES HYDROXY-PYRIMIDINES (URACILES) EN MILIEU APOLAIRE: ETUDE INFRA-ROUGE
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In contrast to what observed with mono hydroxy-pyridines and -pyrimidines the lactim-lactam equilibrium of uracils is not found to be markedly influenced by solvent polarity.
- Chevrier, Marianne,Bensaude, Olivier,Guillerez, Jean,Dubois, Jacques-Emile
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p. 3359 - 3362
(2007/10/02)
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