- Vapor phase phototransposition chemistry of dimethylpyrazines and dimethylpyrimidines
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Based on their phototransposition chemistry, the three dimethylpyrazines and four dimethylpyrimidines can be arranged into two groups. 2,5-Dimethylpyrazine, 2,5-dimethylpyrimidine, and 4,6-dimethylpyrimidine constitute a photochemical triad. Irradiation of any one member of the triad in the vapor phase results in the formation of the other two members. The other four isomers, 2,6-dimethylpyrazine, 2,3-dimethylpyrazine, 2,4- dimethylpyrimidine, and 4,5-dimethylpyrimidine constitute a photochemical tetrad. Irradiation of any one member results in the formation of the other three. In addition, 2,4-dimethylpyrimidine and 2,6-dimethylpyrazine also photoisomerize to 3,6-dimethylpyridazine. Irradiation of the last in the vapor state resulted in the four members of the tetrad.
- Pavlik, James W.,Vongakorn, Tharinee,Kebede, Naod
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p. 216 - 228
(2017/11/17)
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- A C-13 nuclear magnetic resonance study of the pyrimidine synthesis by the reactions of 1,3-dicarbonyl compounds with amidines and ureas
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The detailed mechanistic pathways are elucidated for the reactions of acetylacetone, methyl acetoacetate, and dimethyl malonate with a variety of amidines and ureas.In many cases the identification of a single intermediate allows the definition of the reaction path and identification of two steps.Intermediates characterized include ring-closed dihydroxytetrahydropyrimidines, dihydrohydroxypyrimidinones, open-chain enamides, and carbonyl addition compounds.
- Katritzky, Alan R.,Yousaf, Taher I.
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p. 2087 - 2093
(2007/10/02)
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- POLAR EFFECTS IN THE HOMOLYTIC METHYLATION OF PYRIMIDINE: ORIENTATION AND POLYSUBSTITUTION
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The homolytic methylation of pyrimidine in aqueous solution has been investigated with three different radical sources: tBuOOH-Fe(2+), MeCO2H-S2O8(2-)-Ag(1+), and MeSOMe-H2O2-Fe(2+).This last reagent, used for the first time in homolytic aromatic substitution, turned out to be the most efficient.The orientation of mono- and poly-methylated derivatives is discussed on the basis of polar effects.
- Giordano, Claudio,Minisci, Francesco,Tortelli, Vito,Vismara, Elena
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p. 293 - 296
(2007/10/02)
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- On the Reactivity of N-Benzylpyrimidinium Salts with Nitrogen Nucleophiles (1,2)
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Treatment of the 1-benzyl salts of pyrimidine, 4,6-dimethylpyrimidine, and 4-t-butylpyrimidine with liquid ammonia leads to debenzylation.The 1H-nmr spectroscopic evidence is presented that the initial step in the debenzylation of 1-benzyl-4,6-dimethylpyrimidinium bromide is the addition of the ammonia at C-2, while with 1-benzyl-4-t-butylpyrimidinium bromide the addition takes place at C-6.It is proved by 15N labelling that the debenzylation occurs according to the ANRORC mechanism.The above-mentioned 1-benzylpyrimidinium bromides give with hydrazine, pyrazole, 3,5-dimethylpyrazole and 3-t-butylpyrazole, respectively.
- Dlugosz, A.,van der Plas, H.C.,van Veldhuizen, A.
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p. 373 - 375
(2007/10/02)
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