On benzo[b][1,4]diazepinium-olates, -thiolates and -carboxylates as anti-Hückel mesomeric betaines
作者:Andreas Schmidt、Abbas Gholipour Shilabin、Martin Nieger
DOI:10.1039/b308412d
日期:——
2,3-Diaminophenol 4, 3,4-diaminophenol 5, 4-methoxy-1,2-diaminobenzene 6, 3,4-diaminobenzenethiol 7, 2,3-diaminobenzoic acid 8, and 3,4-diaminobenzoic acid 9 were reacted with 2,4-pentanedione to yield the corresponding benzo[b][1,4]diazepinium salts, respectively. The hydroxy-benzo[b][1,4]diazepinium salts 17 and 18 do not form mesomeric betaines (MB) on deprotonation. Instead, they are converted into the diimines 24 and 25. By contrast, the 7-mercaptobenzo[b][1,4]diazepinium salt 20 yields the corresponding thiolate on increasing the pH of the solution. This MB, which possesses 4n
π-electrons, does not fit into the classification system of heterocyclic mesomeric betaines accepted today. Deprotonation of the betaine results in the formation of an instable anionic thiolate 31 which oxidizes immediately to the disulfide 32. The carboxy derivatives 21 and 22 readily form cross-conjugated mesomeric betaines. Whereas the diimine 34 proved to be instable, the sodium salt of the diimine 36 was unambiguously characterized. An X-ray single crystal analysis of 22 as its picrate is presented in order to gain additional insights into these 4n
π-electron systems.
将 2,3-二氨基苯酚 4、3,4-二氨基苯酚 5、4-甲氧基-1,2-二氨基苯 6、3,4-二氨基苯硫酚 7、2,3-二氨基苯甲酸 8 和 3,4-二氨基苯甲酸 9 与 2,4-戊二酮反应,分别生成相应的苯并[b][1,4]二氮杂卓盐。羟基苯并[b][1,4]二氮杂卓盐 17 和 18 在去质子化过程中不会形成间位甜菜碱(MB)。相反,它们会转化为二亚胺 24 和 25。相比之下,7-巯基苯并[b][1,4]二氮杂卓盐 20 在溶液 pH 值升高时会生成相应的硫代硫酸盐。这种拥有 4n π 电子的甲基溴并不符合当今公认的杂环间位甜菜碱分类系统。甜菜碱的去质子化会形成一种不稳定的阴离子硫代硫酸盐 31,这种硫代硫酸盐会立即氧化成二硫化物 32。羧基衍生物 21 和 22 很容易形成交叉共轭的中间体甜菜碱。虽然二亚胺 34 被证明是不稳定的,但二亚胺 36 的钠盐却得到了明确的表征。为了进一步了解这些 4n π-电子系统,本研究对 22 的皮酸盐进行了 X 射线单晶分析。