Photocatalytic Reductive C-O Bond Cleavage of Alkyl Aryl Ethers by Using Carbazole Catalysts with Cesium Carbonate.
Photocatalytic Reductive C-O Bond Cleavage of Alkyl Aryl Ethers by Using Carbazole Catalysts with Cesium Carbonate.
复制标题
使用碳酸铯咔唑催化剂光催化还原烷基芳基醚的 C-O 键断裂。
DOI：
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发表时间：
2021
影响因子：
3.6
通讯作者：
R. Matsubara
中科院分区：
文献类型：
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作者：
T. Yabuta;M. Hayashi;R. Matsubara
活化相对稳定的醚C-O键并将其转化为其它官能团的方法是期望的。醚的单电子还原是裂解C-O键的一种潜在的有前途的途径。然而，由于烷基芳基醚的高度负的氧化还原电位（Ered <-2.6V vs SCE），醚C-O键活化的这种模式具有挑战性。在此，我们报告了可见光诱导的光催化裂解的烷基芳基醚C-O键使用咔唑基的有机光催化剂（PC）。苄型和非苄型芳基醚均经历C-O键断裂以形成相应的苯酚产物。添加Cs2 CO 3是有益的，特别是在使用N-H咔唑PC的反应中。该反应被认为是通过单电子转移（SET）从激发态咔唑到底物醚。N-H咔唑PC与Cs 2CO 3通过氢键存在相互作用，这使得去质子辅助的电子转移机制能够发挥作用。此外，刘易斯酸性Cs阳离子与底物烷基芳基醚相互作用以将其活化为电子受体。咔唑的高还原能力与Cs2 CO 3的有益作用相结合，使得这种原本强大的SET事件成为可能。
Methods to activate the relatively stable ether C-O bonds and convert them to other functional groups are desirable. One-electron reduction of ethers is a potentially promising route to cleave the C-O bond. However, owing to the highly negative redox potential of alkyl aryl ethers (Ered < -2.6 V vs SCE), this mode of ether C-O bond activation is challenging. Herein, we report the visible-light-induced photocatalytic cleavage of the alkyl aryl ether C-O bond using a carbazole-based organic photocatalyst (PC). Both benzylic and non-benzylic aryl ethers underwent C-O bond cleavage to form the corresponding phenol products. Addition of Cs2CO3 was beneficial, especially in reactions using a N-H carbazole PC. The reaction was proposed to occur via single-electron transfer (SET) from the excited-state carbazole to the substrate ether. Interaction of the N-H carbazole PC with Cs2CO3 via hydrogen bonding exists, which enables a deprotonation-assisted electron-transfer mechanism to operate. In addition, the Lewis acidic Cs cation interacts with the substrate alkyl aryl ether to activate it as an electron acceptor. The high reducing ability of the carbazole combined with the beneficial effects of Cs2CO3 made this otherwise formidable SET event possible.