建立绿色无氨伯奇还原反应——新型电子盐体系的探索与应用

Birch reduction has been widely used in the reduction of aromatic compounds, which bridged the gulf between aromatic and alicyclic molecules. Recently, the venerated Birch reduction has been applied in new emerging areas, such as the synthesis of hydrogenated graphene. However, this reaction requires toxic solvent, liquid ammonia, which causes operational problems, and the chemoselectivity of Birch reduction is quite low. Unfortunately, there was no alternative synthetic method to replace Birch reduction. In this study, we will synthesize and screen a series of alkali metal/crytand electrides, and employ the most suitable new electride, instead of the alkali metal/ammonia electride, for the development of this green ammonia-free Birch reduction. Compared with the traditional Birch reduction, this new reaction is supposed to be easier to operate, safer and with better chemoselectivity. Our exciting preliminary results demonstrated that alkali metal/crytand electrides are able to achieve the ammonia-free Birch reduction and revealed the first example of a modified Birch reduction tolerating a non-benzylic amide group. Those results exhibited the first application of the alkali metal/crytand electride in organic synthesis. In this work, the alkali metal/crytand electride will be further optimized based on the preliminary results. The reaction condition optimization and the substrate scope investigation of the green ammonia free Birch reduction will be carried out. And the application of this ammonia-free Birch reaction in other emerging fields, such as the synthesis of hydrogenated graphene, will also be evaluated.

伯奇还原反应被广泛应用于芳香族化合物的还原中,被誉为芳香族化合物与脂环化合物之间的桥梁。近年来，该反应在氢化石墨烯合成等新领域中的应用也受到了越来越多的关注。但该反应需要使用大量有毒溶剂——液氨，操作复杂，且化学选择性较差。然而现阶段尚未出现可完全替代伯奇反应的合成方法。本项目拟设计并筛选新型碱金属/穴醚（冠醚）电子盐以代替传统伯奇反应中的碱金属/液氨电子盐体系，并以此为基础建立操作更简单、更安全、化学选择性更好的绿色无氨伯奇反应。前期的研究显示碱金属/穴醚电子盐能够在无氨条件下实现伯奇还原反应，且该体系已经成功实现了第一例可兼容非苄位取代酰胺基的改良伯奇反应。这也是碱金属/穴醚电子盐在有机合成中的首次应用。本项研究将在上述发现的基础上进一步优化碱金属/穴醚(或冠醚)电子盐体系，完成绿色无氨伯奇反应的条件优化、底物拓展等工作。并进一步研究该反应在氢化石墨烯合成等新兴领域中的应用。

伯奇还原反应是重要的芳香族化合物的还原方法,被誉为芳香族化合物与脂环化合物之间的桥梁。此外，伯奇还原条件还被广泛的应用于多类有机分子官能团的转化反应。然而，该反应需要使用大量有毒溶剂——液氨，操作复杂，且化学选择性较差。长期以来，建立一个可以完全替代传统伯奇反应的合成方法一直是一个技术难点。本项目设计并合成了一系列新型碱金属/穴醚（冠醚）电子盐体系。从中筛选出了Na/15-crown-5电子盐体系，可以成功的代替传统伯奇反应中的碱金属/液氨电子盐体系。我们以其为基础建立了操作更简单、更安全、化学选择性更好的绿色无氨伯奇反应。这个方法首次实现了在无氨（低沸点胺）的条件下对包括富电子的苯衍生物在内的芳香化合物的伯奇还原反应。..另外，Na/15-crown-5电子盐体系还被进一步应用于改进其他需要使用传统伯奇还原条件的官能团转化反应。此外，Na媒介的单电子转移反应还被进一步用于氢化石墨烯合成、单电子转移还原氘化反应等新兴领域。