NHC-catalysed, chemoselective crossed-acyloin reactions
NHC-catalysed, chemoselective crossed-acyloin reactions
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DOI：
10.1039/c2sc00622g
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发表时间：
2012-01-01
期刊：
影响因子：
8.4
通讯作者：
Zeitler, Kirsten
中科院分区：
文献类型：
--
作者：
Rose, Christopher A.;Gundala, Sivaji;Zeitler, Kirsten
已经首次表明，相对缺电子的三唑鎓前催化剂促进（在碱存在下在低负载下）醛和α-酮酯之间的高度化学选择性交叉偶姻缩合反应，以提供具有相当大的合成潜力的包含季立体中心的密集官能化产物。可以完全避免迄今在这些反应中占主导地位的加氢酰化途径。该方法的范围是非常广泛的，相对于两个耦合伙伴，和初步研究已经建立的原则，高度的立体化学控制的反应也可以通过使用手性NHC前体。还首次表明，苄基α-酮酯与醛的偶联，然后酰化和简单的氢解以高产率纯化了形式上由两种不同脂肪族醛的化学选择性1：1偶联衍生的产物，并且绝对控制了哪种偶联配偶体表现为酰基阴离子等价物。
It has been shown for the first time that relatively electron deficient triazolium pre-catalysts promote (at low loadings in the presence of base) highly chemoselective crossed acyloin condensation reactions between aldehydes and alpha-ketoesters to afford densely functionalized products incorporating a quaternary stereocentre of considerable synthetic potential. Hydroacylation pathways which have hitherto been dominant in these reactions can be completely avoided. The scope of the process is extraordinarily broad with respect to both coupling partners, and a preliminary study has established the principle that a high degree of stereochemical control over the reaction can also be exercised via the use of a chiral NHC precursor. It has also been shown for the first time that coupling of benzyl alpha-ketoesters with aldehydes followed by acylation and simple hydrogenolysis furnishes a product formally derived from the chemoselective 1 : 1 coupling of two different aliphatic aldehydes in high yield with absolute control over which coupling partner behaves as the acyl-anion equivalent.