General and Mild Cobalt-Catalyzed C-Alkylation of Unactivated Amides and Esters with Alcohols
作者:Nicklas Deibl、Rhett Kempe
DOI:10.1021/jacs.6b06448
日期:2016.8.31
The borrowinghydrogen or hydrogen autotransfer methodology is an elegant and sustainable or green concept to construct carbon-carbon bonds. In this concept, alcohols, which can be obtained from barely used and indigestible biomass, such as lignocellulose, are employed as alkylating reagents. An especially challenging alkylation is that of unactivated esters and amides. Only noble metal catalysts based
借用氢或氢自动转移方法是构建碳-碳键的优雅且可持续或绿色的概念。在这个概念中,可以从几乎不使用且难以消化的生物质(例如木质纤维素)中获得的醇被用作烷基化试剂。一个特别具有挑战性的烷基化是未活化的酯和酰胺。仅使用基于铱和钌的贵金属催化剂来完成这些反应。在此,我们报告了醇对未活化酰胺和酯的第一个贱金属催化的 α-烷基化反应。我们实验室最近开发的钳形配体稳定的钴配合物可以非常有效地催化这些反应。预催化剂可以很容易地从市售的起始材料以多克规模合成,并且在碱性反应条件下自活化。这种 Co 催化剂类别还能够介导酯和酰胺的烷基化反应。此外,我们应用该方法合成酮并将醇转化为由两个碳原子拉长的醛。
Triphenylphosphine dibromide: a simple one-pot esterification reagent
作者:Christophe Salomé、Harold Kohn
DOI:10.1016/j.tet.2008.10.062
日期:2009.1
We report a one-pot, expedient protocol for the conversion of carboxylic acids to their esters using excess triphenylphosphinedibromide, base, and the alcohol. The reaction gave the esterified product in moderate-to-high yields (30–95%). For chiral acids, the reaction proceeded with little or no racemization. Use of a chiral alcohol in this transformation gave the ester with retention of configuration
Magnesium in methanol was found to be an effective and inexpensive reagent for the dehalogenation of (hetero)aryl chlorides, bromides and iodides under mild conditions. The halogen/hydrogen exchange proceeded at room temperature and tolerated functional groups such as esters, nitriles, alcohols, and alkenes.