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Jürgen Liebscher - One of the best experts on this subject based on the ideXlab platform.
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Reaktionen von 1,3‐Dipolen mit Heterocyclen, 9. Umsetzungen von Nitriliminen mit Pyrazinen, Pyrimidinen und 1H‐Pyrimidinthionen
Liebigs Annalen der Chemie, 1994Co-Authors: Lutz Grubert, B. Riemer, Michael Pätzel, Werner Jugelt, Jürgen LiebscherAbstract:Reactions of 1,3-Dipoles with Heterocycles, 9. – Reactions of Nitrilimines with Pyrazines, Pyrimidines and 1H-Pyrimidinethiones Analogous to the synthesis of 1,3-diaryl-1,8a-dihydro-1,2,4-triazolo[4,3-a]pyridines by 1,3-dipolar cycloaddition of diarylnitrilimines with pyridines, the C=N bonds of pyrazine and pyrimidine regio- and stereoselectively react as heterodipolarophiles with nitrilimines 2, generated in situ by dehydrohalogenation of corresponding hydrazonoyl chlorides 1. Whereas in the reaction with pyrazine the biscycloadducts 1,10,10a,10b-tetrahydrodi[1,2,4]triazolo[4,3-a:3′,4′-c] pyrazines 4 were obtained, the interaction of 2 with pyrimidines gave rise to stable monocycloadducts 5, 6 and 7 (1,8a-dihydro-1,2,4-triazolo[4,3-a]pyrimidines). Furthermore a study of the cycloaddition behaviour of a series of pyrimidine-2(1H)-thiones and -4(1H)-thiones with nitrilimines has been carried out. From the different kinds of potentially reactive sites under normal reaction conditions exclusively the semicyclic C=S bond of Pyrimidinethiones shows a cycloaddition reaction to give the corresponding spiro[pyrimidine-4(1H),2′(3′H)-[1,3,4]thiadiazoles] 8 and 9. Using a large excess of nitrilimine in the cycloaddition with pyrimidine-2(1H)-thiones 2:1-cycloadducts 10 were formed.
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Synthesis of pyrimido[2,1-b]benzoxazolium, pyrimido[2,1-b]benzothiazolium and pyrimido[1,2-a]benzimidazolium salts by reaction of 3-isothiocyanato-2-propeniminium salts with o-functionalized anilines
Synthesis, 1993Co-Authors: B. Riemer, Jürgen LiebscherAbstract:3-Isothiocyanato-2-propeniminium salts I react with o-phenylenediamine, o-aminophenol or o-aminothiophenol to give o-substituted 1-phenyl-2(1H)-Pyrimidinethiones 4, which cyclize upon treatment with methyl iodide to afford pyrimido[2,1-b]benzoxazolium, pyrimido[2,1-b]benzothiazolium and pyrimido[1,2-a]benzimidazolium salts 5 (X=O, S or NH, respectively) by a new condensation reaction
Fillmore Freeman - One of the best experts on this subject based on the ideXlab platform.
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Electrochemical oxidation of 2-pyrimidinethiols and theoretical study of their dimers, disulfides, sulfenyl radicals, and tautomers.
The journal of physical chemistry. A, 2008Co-Authors: Fillmore Freeman, Ximeng WangAbstract:The relative energies and structures of 2-pyrimidinethiol (1), 4-methyl-2-pyrimidinethiol (3), 5-methyl-2-pyrimidinethiol (5), and 4,6-dimethylpyrimidinethiol (7), and their dimers, disulfides, sulfenyl radicals, and tautomers have been studied using restricted and unrestricted ab initio theory, density functional theory, complete basis set methods, coupled cluster theory, and quadratic configuration interaction calculations. The electrochemical oxidation of 2-pyrimidinethiol (1), 4-methyl-2-pyrimidinethiol (3), and 4,6-dimethylpyrimidinethiol (7) in ethanenitrile affords the respective disulfides in excellent yields. The less polar 2-pyrimidinethiol tautomers are predicted to be the dominant species in the gas phase. CBS-QB3, CBS-Q, CCD, CCSD(T), QCISD(T), and MP2 predict the energy difference (Erel) between (1) and its tautomer (2-Pyrimidinethione, 2) to be in the narrow range from 7.23 to 7.87 kcal/mol. Similar trends are observed in the Erel values for the respective tautomers of 2-pyrimidinethiols (3...
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Dimers of and tautomerism between 2-pyrimidinethiol and 2(1H)-Pyrimidinethione: a density functional theory (DFT) study.
The journal of physical chemistry. A, 2006Co-Authors: Fillmore FreemanAbstract:Density functional theory (BLYP, B3LYP, B3P86, B3PW91) with the 6-31+G(d,p), 6-311+G(d,p), and cc-pVTZ basis sets has been used to calculate structural parameters, relative energies, and vibrational spectra of 2-pyrimidinethiol (1) and 2(1H)-Pyrimidinethione (2) and their hydrogen-bonded homodimers (C2 3, C2h [4]‡, C2h 5), monohydrates, and dihydrates and a heterodimer (6). Several transition state structures proposed for the tautomerization process have also been examined. At the B3PW91/6-311+G(d,p)//B3PW91/6-31+G(d,p) level of theory 2-pyrimidinethiol (1) is predicted to be 3.41 kcal/mol more stable (Erel) than 2(1H)-Pyrimidinethione (2) in the gas phase and 2 is predicted to be 6.47 kcal/mol more stable than 1 in aqueous medium. An unfavorable planar intramolecular strained four center transition state (TS1) for the tautomerization of 1 and 2 in the gas-phase lies 29.07 kcal/mol higher in energy than 2-pyrimidinethiol (1). The C2 2-pyrimidinethiol dimer (3) is 6.84 kcal/mol lower in energy than the C2 ...
K. P. Butin - One of the best experts on this subject based on the ideXlab platform.
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Complexation in a 5-acylpyrimidine-4-thione—aliphatic diamine—metal(II) chloride system (M = Ni or Co). The molecular structure of fac-tris(5-acetyl-2,4-dimethylpyrimidine-6-thiolato)cobalt(III)
Russian Chemical Bulletin, 2005Co-Authors: E. K. Beloglazkina, A. A. Chizhevskii, V. N. Nuriev, R. L. Antipin, N. V. Zyk, I. V. Chernyshev, A. A. Moiseeva, K. P. ButinAbstract:The reactions of 5-acylpyrimidine-4-thiones with aliphatic diamines in the presence of Ni^II and Co^II salts were studied. New Ni^II and Co^III complexes with ligands of the Pyrimidinethione series were synthesized. The results of the reactions of 5-acetyl-6-methyl-2-phenylpyrimidine-4-thione and 5-acetyl-2,6-dimethylpyrimidine-4-thione with ethylenediamine or 1,3-diaminopropane in the presence of NiCl_2· 6H_2O or CoCl_2·6H_2O depend on (1) the nature of the substituent at position 2 of the pyrimidine ring, (2) the length of the polymethylene bridge between the nitrogen atoms in the diamine molecule, (3) the nature of complex-forming metal, and (4) the Pyrimidinethione: diamine ratio. The resulting complexes were studied by electrochemical methods. The mechanism of electrooxidation and electro-reduction of 5-acylpyrimidine-2-thiones and related nickel and cobalt complexes was proposed. The structures of the complexes were investigated by NMR, UV-Vis spectroscopy, and IR spectroscopy and mass spectrometry. The molecular structure of fac -tris(5-acetyl-2,4-dimethylpyrimidine-6-thiolato)cobalt(III) was established by X-ray diffraction. According to semiempirical quantum-chemical calculations by the PM3(tm) method, both the highest occupied and lowest unoccupied molecular orbitals in the molecules of the compounds under study have a π symmetry and are localized predominantly on the ligand fragments.
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complexation in a 5 acylpyrimidine 4 thione aliphatic diamine metal ii chloride system m ni or co the molecular structure of fac tris 5 acetyl 2 4 dimethylpyrimidine 6 thiolato cobalt iii
Russian Chemical Bulletin, 2005Co-Authors: E. K. Beloglazkina, A. A. Chizhevskii, V. N. Nuriev, R. L. Antipin, N. V. Zyk, I. V. Chernyshev, A. A. Moiseeva, K. P. ButinAbstract:The reactions of 5-acylpyrimidine-4-thiones with aliphatic diamines in the presence of NiII and CoII salts were studied. New NiII and CoIII complexes with ligands of the Pyrimidinethione series were synthesized. The results of the reactions of 5-acetyl-6-methyl-2-phenylpyrimidine-4-thione and 5-acetyl-2,6-dimethylpyrimidine-4-thione with ethylenediamine or 1,3-diaminopropane in the presence of NiCl2· 6H2O or CoCl2·6H2O depend on (1) the nature of the substituent at position 2 of the pyrimidine ring, (2) the length of the polymethylene bridge between the nitrogen atoms in the diamine molecule, (3) the nature of complex-forming metal, and (4) the Pyrimidinethione: diamine ratio. The resulting complexes were studied by electrochemical methods. The mechanism of electrooxidation and electro-reduction of 5-acylpyrimidine-2-thiones and related nickel and cobalt complexes was proposed. The structures of the complexes were investigated by NMR, UV-Vis spectroscopy, and IR spectroscopy and mass spectrometry. The molecular structure of fac-tris(5-acetyl-2,4-dimethylpyrimidine-6-thiolato)cobalt(III) was established by X-ray diffraction. According to semiempirical quantum-chemical calculations by the PM3(tm) method, both the highest occupied and lowest unoccupied molecular orbitals in the molecules of the compounds under study have a π symmetry and are localized predominantly on the ligand fragments.
B. Riemer - One of the best experts on this subject based on the ideXlab platform.
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Reaktionen von 1,3‐Dipolen mit Heterocyclen, 9. Umsetzungen von Nitriliminen mit Pyrazinen, Pyrimidinen und 1H‐Pyrimidinthionen
Liebigs Annalen der Chemie, 1994Co-Authors: Lutz Grubert, B. Riemer, Michael Pätzel, Werner Jugelt, Jürgen LiebscherAbstract:Reactions of 1,3-Dipoles with Heterocycles, 9. – Reactions of Nitrilimines with Pyrazines, Pyrimidines and 1H-Pyrimidinethiones Analogous to the synthesis of 1,3-diaryl-1,8a-dihydro-1,2,4-triazolo[4,3-a]pyridines by 1,3-dipolar cycloaddition of diarylnitrilimines with pyridines, the C=N bonds of pyrazine and pyrimidine regio- and stereoselectively react as heterodipolarophiles with nitrilimines 2, generated in situ by dehydrohalogenation of corresponding hydrazonoyl chlorides 1. Whereas in the reaction with pyrazine the biscycloadducts 1,10,10a,10b-tetrahydrodi[1,2,4]triazolo[4,3-a:3′,4′-c] pyrazines 4 were obtained, the interaction of 2 with pyrimidines gave rise to stable monocycloadducts 5, 6 and 7 (1,8a-dihydro-1,2,4-triazolo[4,3-a]pyrimidines). Furthermore a study of the cycloaddition behaviour of a series of pyrimidine-2(1H)-thiones and -4(1H)-thiones with nitrilimines has been carried out. From the different kinds of potentially reactive sites under normal reaction conditions exclusively the semicyclic C=S bond of Pyrimidinethiones shows a cycloaddition reaction to give the corresponding spiro[pyrimidine-4(1H),2′(3′H)-[1,3,4]thiadiazoles] 8 and 9. Using a large excess of nitrilimine in the cycloaddition with pyrimidine-2(1H)-thiones 2:1-cycloadducts 10 were formed.
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Synthesis of pyrimido[2,1-b]benzoxazolium, pyrimido[2,1-b]benzothiazolium and pyrimido[1,2-a]benzimidazolium salts by reaction of 3-isothiocyanato-2-propeniminium salts with o-functionalized anilines
Synthesis, 1993Co-Authors: B. Riemer, Jürgen LiebscherAbstract:3-Isothiocyanato-2-propeniminium salts I react with o-phenylenediamine, o-aminophenol or o-aminothiophenol to give o-substituted 1-phenyl-2(1H)-Pyrimidinethiones 4, which cyclize upon treatment with methyl iodide to afford pyrimido[2,1-b]benzoxazolium, pyrimido[2,1-b]benzothiazolium and pyrimido[1,2-a]benzimidazolium salts 5 (X=O, S or NH, respectively) by a new condensation reaction
Tsutomu Fujita - One of the best experts on this subject based on the ideXlab platform.
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Generation and amplification of optical activity of axially chiral N-(1-naphthyl)-2(1H)-Pyrimidinethione by crystallization
Organic & biomolecular chemistry, 2010Co-Authors: Masami Sakamoto, Fumitoshi Yagishita, Masaru Ando, Yuich Sasahara, Norifumi Kamataki, Mai Ohta, Takashi Mino, Yoshio Kasashima, Tsutomu FujitaAbstract:X-Ray crystallographic analysis of N-(1-naphthyl)-2(1H)-Pyrimidinethione revealed that the space group was tetragonal and chiral P43. The rate of racemization due to the C–N bond rotation was considerably influenced by the solvent properties. A nonpolar solvent lowers the ΔG‡value by about 3.0 kcal mol−1 relative to the value in a polar or a protic solvent. The crystallization of racemic axially chiral Pyrimidinethione at high temperature led to the chiral breaking of symmetry up to 91% ee.
