Synthesis of 1H-imidazo(1,2-a)pyrazolo(3,4-c)pyridines.
作者:Alain GUEIFFIER、Jean Claude MILHAVET、Yves BLACHE、Olivier CHAVIGNON、Jean Claude TEULADE、Michel MADESCLAIRE、Henry VIOLS、Gerard DAUPHIN、Jean Pierre CHAPAT
DOI:10.1248/cpb.38.2352
日期:——
The reaction of nitrosyl chloride with 6- and 8-acetamido-7-methylimidazo[1, 2-a]pyridine (7g-i) reveal clear differences of reactivity of these isomeric structures. After bifunctionalization of the imidazolic moiety, the 6-acetamido derivatives do not yield the 1H-imidazo[1, 2-a]pyrazolo[4, 5-d]pyridine (4) system, but undergo a Gomberg-Bachman reaction complicated by Dimroth rearrangement. In contrast, upon similar treatment, the 8-acetamido compounds (17, 19) yielded the N-nitrosoacetamides (18a, b), which were converted into 1H-imidazo[1, 2-a]pyrazolo[3, 4-c]pyridines (20a, b) in 22 and 34% yields, respectively, without rearrangement.
亚硝酰氯与 6-和 8-乙酰氨基-7-甲基咪唑并[1, 2-a]吡啶(7g-i)的反应显示,这些异构体结构的反应性存在明显差异。咪唑分子双官能化后,6-乙酰氨基衍生物不会生成 1H-咪唑并[1,2-a]吡唑并[4,5-d]吡啶 (4) 体系,而是会发生与 Dimroth 重排复杂化的 Gomberg-Bachman 反应。相反,8-乙酰氨基化合物(17、19)在经过类似处理后,生成了 N-亚硝基乙酰胺(18a、b),它们分别以 22% 和 34% 的产率转化为 1H-咪唑并[1, 2-a]吡唑并[3, 4-c]吡啶(20a、b),且未发生重排。