Organocatalyzed Birch Reduction Driven by Visible Light.
Organocatalyzed Birch Reduction Driven by Visible Light.
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DOI：
10.26434/chemrxiv.11860221
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发表时间：
2020-02
影响因子：
15
通讯作者：
J. Cole;Dian-Feng Chen;Max Kudisch;Ryan M. Pearson;Chern-Hooi Lim;G. Miyake
中科院分区：
文献类型：
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作者：
J. Cole;Dian-Feng Chen;Max Kudisch;Ryan M. Pearson;Chern-Hooi Lim;G. Miyake
Birch还原是一种强大的合成方法，它使用溶剂化电子将惰性芳烃转化为1，4-环己二烯-用于构建分子复杂性的有价值的中间体。Birch还原传统上使用溶解在氨中的碱金属来产生用于还原未活化的芳烃如苯的溶剂化电子（Ered <-3.42V vs.SCE）。光氧化还原催化剂在高还原性应用中越来越受欢迎，但没有报道显示出足够强的还原电位来还原苯。在这里，我们介绍了苯并[ghi] 苝酰亚胺作为新的有机光氧化还原催化剂，用于在环境温度下进行的桦木还原，并由市售LED的可见光驱动。使用低催化剂负载（<1摩尔%），苯和其它官能化芳烃在完全无金属的反应中以中等至良好的产率选择性地转化为1，4-环己二烯。机理研究支持这种前所未有的可见光诱导的反应性是通过有机光氧化还原催化剂利用来自两个可见光光子的能量来影响单个高能化学转化的能力来实现的。
The Birch reduction is a powerful synthetic methodology that uses solvated electrons to convert inert arenes to 1,4-cyclohexadienes-valuable intermediates for building molecular complexity. Birch reductions traditionally employ alkali metals dissolved in ammonia to produce a solvated electrons for the reduction of unactivated arenes such as benzene (Ered < -3.42 V vs. SCE). Photoredox catalysts have been gaining popularity in highly-reducing applications, but none have been reported to demonstrate reduction potentials powerful enough to reduce benzene. Here, we introduce benzo[ghi]perylene imides as new organic photoredox catalysts for Birch reductions performed at ambient temperature and driven by visible light from commercially available LEDs. Using low catalyst loadings (<1 mole percent), benzene and other functionalized arenes were selectively transformed to 1,4-cyclohexadienes in moderate to good yields in a completely metal-free reaction. Mechanistic studies support that this unprecedented visible light induced reactivity is enabled by the ability of the organic photoredox catalyst to harness the energy from two visible light photons to affect a single, high energy chemical transformation.