NMR Investigations on the Proline-Catalyzed Aldehyde Self-Condensation: Mannich Mechanism, Dienamine Detection, and Erosion of the Aldol Addition Selectivity
作者:Markus B. Schmid、Kirsten Zeitler、Ruth M. Gschwind
DOI:10.1021/jo200431v
日期:2011.5.6
The proline-catalyzed self-condensation of aliphatic aldehydes in DMSO with varying amounts of catalyst was studied by in situ NMR spectroscopy. The reaction profiles and intermediates observed as well as deuteration studies reveal that the proline-catalyzed aldol addition and condensation are competing, but not consecutive, reaction pathways. In addition, the rate-determining step of the condensation
通过原位NMR光谱研究了脯氨酸催化的DMSO中脂肪醛在不同数量的催化剂上的自缩合反应。观察到的反应概况和中间体以及氘代研究表明,脯氨酸催化的醛醇加成和缩合是竞争性的,但不是连续的反应途径。另外,缩合的确定速率的步骤被建议为CC键的形成。我们的发现表明,两个催化剂分子参与了醛醇缩合的C-C键形成,大概是通过曼尼希型途径中的醛醇受体和供体都被激活。已表明该机理在具有高脯氨酸量的乙醛的低聚中也是有效的,为此,完成了对脯氨酸衍生的二烯胺的首次原位检测。竞争性不可逆的醛醇缩合;在这里,NMR反应谱可以用作反应优化的工具。