Protonation of the Electron Adducts of Pyrimidine Derivatives.
作者:Kazue OHKURA、Koh-ichi SEKI
DOI:10.1248/cpb.43.1024
日期:——
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.
5 取代的 1,3-二甲基尿嘧啶(1a-e :a, R=F; b, R=Cl; c, R=H; d, R=CH3;e, R=p-xylyl) 在对二甲苯中,在三氟乙酸 (TFA) 的存在下,以不同的比例得到 5, 6-二氢-1, 3-二甲基-6-对甲基苄基尿嘧啶 (3a-d)、5, 6-二氢-1, 3-二甲基-5-对甲基苄基尿嘧啶 (4a-e) 和 5, 6-二氢-1, 3-二甲基尿嘧啶 (5a-e)。据认为,6-异构体(3)来自于 1 的 O(4)-质子化电子加合物,而 4 和 5 则是 C(6)-质子化电子加合物的产物。(4+5) 与 3 的比例取决于 O(4)-质子化中间产物的电离电位。4+5 的形成随着反式脂肪酸浓度的增加而增加。