We have developed an efficient method for the esterification or thioesterification of equimolar amounts of carboxylic acids and alcohols or thiols using a novel reagent, p-toluenesulfonylchloride (TsCl) together with N-methylimidazole. The present method is simple, mild, and reactive, uses readily available and economical reagents. The choice of amine is critical for the present method. The amine
我们已经开发了一种有效的方法,使用新型试剂对甲苯磺酰氯(TsCl)和N-甲基咪唑对等摩尔量的羧酸,醇或硫醇进行酯化或硫酯化。本方法简单,温和,反应活性强,使用容易获得且经济的试剂。胺的选择对于本方法是至关重要的。胺,N-甲基咪唑具有两个作用:(i)作为HCl清除剂,用于初始平滑生成羧酸和TsCl之间的混合酸酐,以及(ii)由混合酸酐连续形成高反应性的铵中间体。该方法可应用于各种类型的羧酸,醇和硫醇:b)两个N-Cbz氨基酸被平滑酯化而没有外消旋;c)成功制备了不稳定的1β-甲基卡巴培南关键中间体和拟除虫菊酯杀虫剂普乐菌素。还进行了羧酸与伯胺或仲胺之间的相关酰胺形成。拟议的反应机理涉及一种生产反应性酰基lam中间体的新方法。仔细的1 H NMR监测研究合理地支持了这些中间体的生产。
A highly chemoselective and reactive μ‐oxo‐dinuclear iron(III) salen catalyst for transesterification was developed. The developed ironcomplexcatalyzed acylation of aliphatic amino alcohols with nearly perfect O‐selectivity, even when using activated esters, for which chemoselectivity is more difficult to control. In addition, O‐selective transesterification of aromatic amino alcohols was achieved