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刘铸晋等在测定钩吻素子1结构的工作中,发现1能被钠-醇还原裂解,亚胺基β位的醚键发生断裂,得到还原裂解产物——双氢钩吻醇2~([1])。其反应机理可能是一种自由基-阴离子反应,类似于苄基醚的还原断裂。如图式1所示: 反应的关键一步是一个单电子在化合物1中的碳氮双键上的加成,生成一个自由基-阴离子,接着发生β键的断裂及质子化。这种过程连续进行三次以后,就能获得还原裂解产物2。很明显,反应的决速一步是自由基的生成~([2])。为了进一步探讨这一反应的应用范围,我们合成了一系列具有各种亚胺体系的模型化合物,研究他们在钠-醇溶液中的反应情况。这些模型化合物是一系列的Schiff碱(见表1)。
Liuzhuo Jin et al. In the work of determining the structure of kougenin 1, it was found that 1 could be cleaved by sodium-alcohol and the ether bond at β-position of imine was cleaved to obtain the reduced cleavage product, ]). The reaction mechanism may be a free radical - anion reaction, similar to the reduction of benzyl ether rupture. As shown in Scheme 1, the key step of the reaction is the addition of a single electron to the carbon-nitrogen double bond in compound 1 to form a free-anion, followed by cleavage and protonation of the β bond. After this process has been carried out three times in succession, reduced lysis product 2 can be obtained. Obviously, the reaction rate is one step free radical generation ~ ([2]). In order to further explore the application of this reaction, we synthesized a series of model compounds with various imine systems to study their reaction in sodium-alcohol solution. These model compounds are a series of Schiff bases (see Table 1).