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首页> 外文期刊>Catalysis science & technology >Theoretical and experimental studies on the structure-property relationship of chiral N, N'dioxide-metal catalysts probed by the carbonylene reaction of isatin
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Theoretical and experimental studies on the structure-property relationship of chiral N, N'dioxide-metal catalysts probed by the carbonylene reaction of isatin

机译：理论和实验研究手性N的组织性能的关系N 'dioxide-metal催化剂的探索carbonylene靛红的反应

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The structure and electronic properties of metallic complexes formed by coordinating chiral N, N'-dioxide ligands with different amino acid skeletons or straight-chain alkyl spacers (linkage) to Mg2+ and Ca2+ are studied at the B3LYP-D3.BJ)/6-311G**(SMD, CH2Cl2)//ONIOM (B3LYP/6-31G*: UFF) (SMD, CH2 Cl-2) level. The N-oxide unit in the ligand exhibits a stronger O-donor ability than the carbonyl of the amide in the formation of the chiral N, N'-dioxide-Mg.II) catalyst. Coordination of the chiral N, N'-dioxide ligand to the metal center forms a pocket-like chiral environment ("chiral pocket"), which can be characterized by four structural descriptors, which are the bite angle alpha O-1-M-O-2, the average M-O distance, the torsion angle theta(2) (C1-O1 ... O2-C2) and the dihedral angle (DC1-N3-C7-C8 or DC2-N4-C9-C10). The Lewis acidity of the metal ion decreases when the number of -CH2 spacers between two N-oxide units increases from 1 to 5, which is attributed to increasing Pauli repulsion as well as deformation of fragments. The stereoselectivity of asymmetric carbonyl-ene reaction is dependent on the blocking effect of ortho-iPr of aniline on the reaction site of isatin, which could be adjusted by changing the linkage and chiral backbone as well as metal ion. An unfavorable steric arrangement in the re-face attack pathway translated into a more destabilizing activation strain of the ene substrate, enhancing the enantiodifferentiation of two competing pathways for the desired (R)-product. The counterion might change the catalytic species as well as the associated chiral pocket by taking part in coordination towards the metal center, consequently affecting the reaction mechanism and stereoselectivity.
机译：的结构和电子性质协调手性金属配合物形成N, N '二氧化碳配体与不同的氨基酸骨骼或直链烷基间隔器(链接)Mg2 +和Ca2 +进行了研究B3LYP-D3.BJ) / 6-311G * * (SMD,氯甲烷)/ / ONIOM(B3LYP /我感觉*:风浪)(SMD、CH2 Cl-2)水平。N-oxide单元配体的展品更强比的酰胺羰基O-donor能力手性的形成N, N ' -dioxide-Mg.II)催化剂。N的二氧化碳配体形成的金属中心pocket-like手性环境(“手性的口袋里”),可表现为四个结构描述符,咬角αO-1-M-O-2, M-O平均距离,扭转角θ(2)(C1-O1…角(DC1-N3-C7-C8或DC2-N4-C9-C10)。酸度的金属离子减少的时候数量的ch2两个N-oxide单元之间的间距器增加从1到5,这是归因于增加泡利斥力以及变形的碎片。依赖于carbonyl-ene反应阻塞ortho-iPr苯胺的效果靛红的反应网站,可以调整通过改变连杆和手性支柱金属离子。在重构攻击路径安排翻译成一个更不稳定的激活烯基板的应变,提高enantiodifferentiation两个相互竞争的途径对所需的(R)的产品。改变催化物种以及参与相关手性的口袋里对金属中心协调,因此影响了反应机理立体选择性。

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