Highly Enantioselective Ferrocenyl Palladacycle-Acetate Catalysed Arylation of Aldimines and Ketimines with Arylboroxines.
Highly Enantioselective Ferrocenyl Palladacycle-Acetate Catalysed Arylation of Aldimines and Ketimines with Arylboroxines.
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DOI：
10.1002/chem.201605244
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发表时间：
2017-02
期刊：
影响因子：
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通讯作者：
C. Schrapel;W. Frey;D. Garnier;R. Peters
中科院分区：
文献类型：
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作者：
C. Schrapel;W. Frey;D. Garnier;R. Peters
苄基N-取代的立体中心构成药物中常见的结构基序。因此，它们的高度对映选择性生成具有技术重要性。一个有吸引力的策略是亚胺与有机硼试剂的芳基化。手性Rh络合物已经达到了这种反应类型的高水平的生产率。在这篇文章中，我们描述了一个富电子的钯催化剂也表现良好的醛亚胺的芳基化，最好的铑催化剂相比。二茂铁基钯环-乙酸酯催化剂允许宽的底物范围和非常高的对映选择性。通常观察到的副反应如芳基-芳基同偶联和亚胺水解可以被阻断。机理研究表明，a）乙酸酯配体对transmetrobenzene是至关重要的，B）活性催化剂最有可能是钯环-OAc单体，c）速率限制步骤可能是产物释放。通过加入KOAc，芳基化也可以应用于酮亚胺。
Benzylic N-substituted stereocenters constitute a frequent structural motif in drugs. Their highly enantioselective generation is hence of technical importance. An attractive strategy is the arylation of imines with organoboron reagents. Chiral Rh complexes have reached a high level of productivity for this reaction type. In this article we describe that an electron rich PdII catalyst also performs well in the arylation of aldimines, comparable to the best Rh catalysts. The ferrocenyl palladacycle-acetate catalyst allows for a broad substrate scope and very high enantioselectivities. Commonly observed side reactions like aryl-aryl homocouplings and imine hydrolysis could be blocked. Mechanistic studies implicate that a) the acetate ligand is crucial for transmetallation, b) the active catalyst is most likely a palladacycle-OAc monomer, c) the rate limiting step is probably the product release. By added KOAc the arylation could also be applied to ketimines.