N-Heterocyclic Carbene Induced Cycloaddition Reactions of Indazoles with Acetylenes To Form a New Ring System
作者:Andreas Schmidt、Bohdan Snovydovych、Sascha Hemmen
DOI:10.1002/ejoc.200800456
日期:2008.9
but-2-ynedioate (DMAD, DEAD) as the activated triple bond yielded this ring system with an ester group at the 9b-position, which originates from the acetylene derivative. Model reactions were carried out to elucidate the mechanisms of these reactions, and some trapping products of the N-heterocyclic carbene have been characterized. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
内消旋甜菜碱 1,2-二甲基吲唑鎓-3-羧酸盐的热脱羧导致形成 N-杂环卡宾吲唑-3-亚基,其使甜菜碱的第二分子去质子化,得到偶氮甲碱叶立德。该 1,3-偶极在用 3-苯基丙炔酸乙酯或甲基丙酸乙酯处理后经历环加成/脱羧序列,得到新的环系统 3,5-二氢-2H-吡咯并 [1,2-b] 吲唑。相比之下,丁-2-炔二酸二甲酯或二乙酯(DMAD、DEAD)作为活化的三键产生了该环系统,该环系统在 9b 位具有酯基,该基团源自乙炔衍生物。进行模型反应以阐明这些反应的机制,并且已经表征了 N-杂环卡宾的一些捕获产物。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany,