Pd-Catalyzed Debenzylation and Deallylation of Ethers and Esters with Sodium Hydride
作者:Yujian Mao、Ye Liu、Yanwei Hu、Liang Wang、Shilei Zhang、Wei Wang
DOI:10.1021/acscatal.8b00185
日期:2018.4.6
simply that the addition of Pd(OAc)2 as a promotor switches the reactivity of a commonly used base NaH to a nucleophilic reductant. The reactivity is engineered into a palladium-catalyzed reductive debenzylation and deallylation of aryl ethers and esters. This operationally simple, mild protocol displays a broad substrate scope and a broad spectrum of functional group tolerance (>50 examples) and high chemoselectivity
Sulfated tungstate as hydroxyl group activator for preparation of benzyl, including <i>p</i>-methoxybenzyl ethers of alcohols and phenols
作者:Kamlesh V. Katkar、Sachin D. Veer、Krishnacharya G. Akamanchi
DOI:10.1080/00397911.2016.1230218
日期:2016.12.1
ABSTRACT Sulfated tungstate was found to be an effective heterogeneous and reusable catalyst for hydroxy group activation–mediated preparation of benzylic ethers including p-methoxybenzylic ethers of a wide range of alcohols and phenols under mild reaction conditions. GRAPHICAL ABSTRACT
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 bondcleavage 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
激活相对稳定的醚C-O键并将其转化为其他官能团的方法是理想的。醚的单电子还原是裂解C-O键的潜在途径。然而,由于烷基芳基醚的高度负氧化还原电势(E red <-2.6 V vs SCE),这种醚C–O键活化方式具有挑战性。在本文中,我们报告了使用咔唑基有机光催化剂(PC)的可见光诱导的烷基芳基醚C–O键的光催化裂解。苄基和非苄基芳基醚均经过C–O键裂解形成相应的苯酚产物。添加Cs 2 CO 3是有益的,特别是在使用NH咔唑PC的反应中。建议该反应通过从激发态咔唑到底物醚的单电子转移(SET)进行。N – H咔唑PC通过氢键与Cs 2 CO 3相互作用,这使得去质子辅助的电子转移机制得以运行。另外,路易斯酸性Cs阳离子与底物烷基芳基醚相互作用以活化它作为电子受体。咔唑的高还原能力与Cs 2 CO 3的有益作用相结合,使这种原本可怕的SET事件成为可能。