- Protonation of the electron adducts of pyrimidine derivatives
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Photolyses of 5-substituted 1,3-dimethyluracils (1a-e: a, R = F; b, R = Cl; c, R = H; d, R = CH3; e, R = p-xylyl) in p-xylene in the presence of trifluoroacetic acid (TFA) afforded 5,6-dihydro-1,3-dimethyl-6-p-methylbenzyluracils (3a-d), 5,6-dihydro-1,3-dimethyl-5-p-methylbenzyluracils (4a-e), and 5,6-dihydro-1,3-dimethyluracils (5a-e) in varying ratios. It is suggested that the 6-isomers (3) are derived from the O(4)-protonated electron adducts of 1, while 4 and 5 are the products from the C(6)-protonated electron adducts. The ratio of (4 + 5) vs. 3 depends on the ionization potentials of the O(4)-protonated intermediates. The formation of 4 + 5 increases with increasing concentration of TFA.
- Ohkura,Seki
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p. 1024 - 1027
(2007/10/03)
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- ACID CATALYZED PHOTOREACTION OF 5-CHLORO-1,3-DIMETHYLURACIL WITH SUBSTITUTED BENZENES
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The photo-induced substitution of 5-chloro-1,3-dimethyluracil with substituted benzenes, affording the corresponding 5-aryl-1,3-dimethyl-uracils in appreciable yields, was significantly promoted by the addition of trifluoroacetic acid to the reaction mixture.
- Ohkura, Kazue,Matsuda, Kohki,Seki, Koh-ichi
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p. 1371 - 1376
(2007/10/02)
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- Photoreaction of 5-Bromo-1,3-dimethyluracil with 1,4-Xylene. The Effect of Acid
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The photoreaction of 5-bromo-1,3-dimethyluracil in 1,4-xylene solution yields a mixture of 5- and 6-aryl substituted uracils.The 5-isomer is formed first and is followed by the 6-isomer, the latter being the product from protonated uracil.In the presence of initially added acid (HBr and trifluoroacetic acid) both isomers are formed simultaneously.
- Seiki, Koh-ichi,Matsuda, Kohki,Ohkura, Kazue
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p. 175 - 176
(2007/10/02)
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- PHOTOLYSIS OF 5-BROMO-1,3-DIMETHYLURACIL IN SUBSTITUTED BENZENES
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Photolysis of 5-bromo-1,3-dimethyluracyl in toluene, xylene and anisole afforded the anormalously substituted 6-aryl-1,3-dimethyluracils beside the expected products 5-aryl-1,3-dimethyluracils, while the reaction with veratrole occured exclusively at the 5-position of the uracil ring.
- Seki, Koh-ichi,Bando, Yuko,Ohkura, Kazue
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p. 195 - 196
(2007/10/02)
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