木质素是生产可再生芳香化学品的潜在原料。然而,木质素衍生的芳烃被严重甲氧基化,这会影响它们在一些下游增值尝试中的反应性。在此,我们报告了一种在温和条件下使用酸性浓溴化锂 (ACLB) 对木质素解聚衍生的芳烃进行去甲基化的有效方法(例如, 1.5 M HCl, 110 °C, 和 2 h). 具有一个或两个甲氧基(G 型和 S 型)、烷基羟基和羰基以及供电子和吸电子取代基的芳烃用于研究去甲基化机制。S 型芳烃比它们的 G 型类似物去甲基化更快。烷基羟基在该条件下被溴化。羰基(醛和酮)促进了不受欢迎的缩合。给电子取代基促进去甲基化,而吸电子取代基延迟去甲基化。由于稳定中间体的形成,邻位羧基增强了去甲基化。
Nanomagnetic zirconia-based sulfonic acid (Fe<sub>3</sub>O<sub>4</sub>@ZrO<sub>2</sub>-Pr-SO<sub>3</sub>H): a new, efficient and recyclable solid acid catalyst for the protection of alcohols via HMDS under solvent free conditions
alcohols using hexamethyldisilazane (HMDS) under solvent-free conditions at room temperature. The solid nanocatalyst can easily be separated and reused several times without significant loss of its catalytic activity. Also, in addition to its being inexpensive and the simplicity of the separation process, this heterogeneouscatalyst has shown a good chemoselectivity in the reactions.
在本工作中,通过(3-巯基丙基)三甲氧基硅烷与纳米磁性氧化锆的反应来制备磺酸官能化的纳米磁性氧化锆。然后,通过过氧化氢和H 2 SO 4直接氧化硫醇基,合成了纳米氧化锆基磺酸(Fe 3 O 4 @ZrO 2 -Pr -SO 3 H)。随后。通过傅里叶变换红外光谱(FT-IR),场发射扫描电子显微镜(FE-SEM)成像,能量色散X射线光谱(EDX),X射线衍射(XRD)测量和振动样品磁力分析法对催化剂进行了表征( VSM)。六甲基二硅氮烷(HMDS)在无溶剂条件下于室温下用作具有高催化活性的有效纳米催化剂,用于保护醇。固体纳米催化剂可以容易地分离并重复使用数次,而不会显着降低其催化活性。而且,除了其廉价和分离过程的简便性之外,这种非均相催化剂在反应中还显示出良好的化学选择性。
A convenient synthesis of 1,3-oxazolidin-4-ones and 1,3-oxazin-4-ones
作者:Klaus Th. Wanner、Ulrich Weber
DOI:10.1002/jhet.5570340256
日期:1997.3
1,3-Oxazolidin-4-ones and 1,3-oxazin-4-ones were synthesized by formal cyclocondensation of imines with α- or β-hydroxy acids.
Notes - Trimethylsilyl Derivatives of Hydroxy Aromatic Acids
作者:Charles Burkhard
DOI:10.1021/jo01356a622
日期:1957.5
Nano Fe<sub>3</sub>O<sub>4</sub>@ZrO<sub>2</sub>/SO<sub>4</sub><sup>2−</sup>: A highly efficient catalyst for the protection and deprotection of hydroxyl groups using HMDS under solvent-free condition
the protection and deprotection process of various types of alcohols and phenols by HMDS in the presence of nano magnetic sulfated zirconia (Fe3O4@ZrO2/SO42−) as a solid acidcatalyst under very mild and solvent-free condition. This method has interesting advantages like short reaction times and a simple workup process. With regard to some outstanding benefits of this new heterogeneous catalyst such
Efficient <i>O</i>-demethylation of lignin-derived aromatic compounds under moderate conditions
作者:Yueqing Wang、Mingjie Chen、Yang Yang、John Ralph、Xuejun Pan
DOI:10.1039/d3ra00245d
日期:——
Lignin is a potential feedstock to produce renewable aromatic chemicals. However, lignin-derived aromatics are heavily methoxylated, which affects their reactivity in some downstream valorization attempts. Herein, we report an efficient method for the demethylation of the aromatics derived from lignin depolymerization using acidic concentrated lithium bromide (ACLB) under moderate conditions (e.g.
木质素是生产可再生芳香化学品的潜在原料。然而,木质素衍生的芳烃被严重甲氧基化,这会影响它们在一些下游增值尝试中的反应性。在此,我们报告了一种在温和条件下使用酸性浓溴化锂 (ACLB) 对木质素解聚衍生的芳烃进行去甲基化的有效方法(例如, 1.5 M HCl, 110 °C, 和 2 h). 具有一个或两个甲氧基(G 型和 S 型)、烷基羟基和羰基以及供电子和吸电子取代基的芳烃用于研究去甲基化机制。S 型芳烃比它们的 G 型类似物去甲基化更快。烷基羟基在该条件下被溴化。羰基(醛和酮)促进了不受欢迎的缩合。给电子取代基促进去甲基化,而吸电子取代基延迟去甲基化。由于稳定中间体的形成,邻位羧基增强了去甲基化。