Heterocycles structurally influenced by a side chain.<b>X</b>. Effect of temperature and side chain on the imine-enamine tautomerism in the quinoxalinone and pyridopyrazinone systems
作者:Taketsugu Seki、Yasuo Iwanami、Yoshiyuki Kuwatani、Masahiko Iyoda
DOI:10.1002/jhet.5570340312
日期:1997.5
3-(1-ethoxycarbonyl)ethyl-1H-pyrido[2,3-b]-pyrazin-2-one (8), and 3-(1-benzoyl)ethyl-1H-quinoxalin-2-one (9) exist only in the imine form due to the steric effect of the methyl substituent. As regards the imine-enamine tautomerism, 3-(β-carbonylmethylene) derivatives of 1,2-dihydro-4H-pyrido[2,3-b]pyrazin-3-one such as 12 and 15–18 gradually change from the enamine form to the imine form with elevated temperatures;
3-(1-苯甲酰基)乙基-1 H-吡啶[2,3 - b ]吡嗪-2-酮(7),3-(1-乙氧羰基)乙基-1 H-吡啶[2,3- b ]-由于甲基取代基的空间效应,吡嗪-2-酮(8)和3-(1-苯甲酰基)乙基-1 H-喹喔啉-2-酮(9)仅以亚胺形式存在。关于亚胺-烯胺互变异构现象,1,2-二氢-4 H-吡啶并[2,3 - b ]吡嗪-3-一的3-(β-羰基亚甲基)衍生物如12和15-18逐渐变化。在高温下烯胺形式变为亚胺形式;但是3,4-二氢-1的3-(羰基亚甲基)衍生物ħ -吡啶并[2,3- b ]吡嗪-2-酮,为这样的10,19和20示出小的温度效应。2-苯乙叉基-1,2-二氢-4 H-吡啶并[3,4- b ]吡嗪-3-一(21)和3-苯乙叉基-3,4-二氢-1 H-吡啶并[3,4- b以烯胺形式存在的]吡嗪-2-酮(22)没有温度作用。