Nucleophilic Carbenes and Pseudo-Cross-Conjugated Mesomeric Betaines of Indazole Starting from Analogues of the Alkaloid-Betaine Nigellicine
作者:Andreas Schmidt、Lars Merkel、Wolfgang Eisfeld
DOI:10.1002/ejoc.200500032
日期:2005.5
ted mesomeric betaines. Indazolium-3-carboxylate, prepared starting from indazole-3-carboxylic acid by an esterification–methylation–saponification sequence, can be converted into the isoconjugated phenyl- and 4-(nitrophenyl)amidates and the thiocarboxylate as additional examples of pseudo-cross-conjugated systems. In accordance with results of ab initio calculations decarboxylation of indazolium-3-carboxylate
生物碱 Nigellicine 具有 indazolium-3-carboxylate 环系统作为电子相关的部分结构,它代表了伪交叉共轭甜菜碱类的成员。Indazolium-3-carboxylate, 从 indazole-3-羧酸通过酯化-甲基化-皂化序列制备,可以转化为异共轭苯基-和 4-(硝基苯基)酰胺和硫代羧酸盐作为假交叉的附加例子共轭系统。根据 ab initio 计算的结果,indazolium-3-carboxylate 脱羧与亲核卡宾 indazol-3-ylidene 的形成在大约 40 °C 开始,如温度相关的 NMR 光谱所证明。卡宾可以以吲唑盐的形式被质子捕获,和二氧化碳,其重构拟交叉共轭的内消旋甜菜碱。根据计算,卡宾采用单线态基态。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)