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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Constrained geometry aminooxazolinate ligands giving chiral zirconium guanidinates; catalytic cyclohydroamination
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Constrained geometry aminooxazolinate ligands giving chiral zirconium guanidinates; catalytic cyclohydroamination

机译：几何形状受限的氨基恶唑啉酸酯配体，得到手性锆胍;催化环氢化胺化

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DFT calculations indicate that contrary to a prior report, N-heterocycle-augmented constrained geometry ligands e. g. Cp '-SiMe2-NR (Cp ' = Me4C5, R = 2-pyridine) should be capable of binding both atoms of the diazaallyl fragment at zirconium. This was confirmed by a molecular structure of a previously reported complex. Similar R = 2-oxazoline complexes were also shown to be feasible, although an additional N,O binding mode was accessible. The proligands HCp '-SiMe2-NHR (R = chiral non-racemic 2-oxazoline) were readily synthesised in high yield via base mediated reaction of 2-aminooxazolines and Cp '-SiMe2Cl. Subsequent reaction with Zr(NMe2)(4) gave, rather than the desired complexes, configurationally stable chiral-at-zirconum guanidinate/alkoxide chelate products; the aminooxazolinate units had undergone ring-opening and migratory insertion of -NMe2. Trends in the level diastereoselection follow the steric demand of the oxazoline substituent, with the larger groups (Bu-t, Pr-i) giving single diastereomers. The modest performance of these guanidinate compounds in enantioslective catalytic cyclohydroamination of aminoalkenes follows the expected trends for metal accessibility in a sigma-amido insertative mechanism.
机译：DFT计算表明，与先前的报道相反，N-杂环增强的约束几何配体e。 G。 Cp′-SiMe2-NR（Cp′＝ Me4C5，R ＝ 2-吡啶）应能够结合锆上二氮烯丙基片段的两个原子。先前报道的复合物的分子结构证实了这一点。相似的R = 2-恶唑啉配合物也被证明是可行的，尽管可以使用其他的N，O结合模式。通过2-氨基恶唑啉和Cp′-SiMe2Cl的碱介导反应，容易以高收率合成配体HCp′-SiMe2-NHR（R ＝手性非外消旋2-恶唑啉）。随后与Zr（NMe2）（4）反应，得到所需构型稳定的手性锆锆胍/醇盐螯合物产物，而不是所需的络合物。氨基恶唑啉酸酯单元经历了-NMe 2的开环和迁移插入。非对映体选择性的趋势遵循恶唑啉取代基的空间需求，较大的基团（Bu-t，Pr-i）给出单一的非对映体。这些胍盐化合物在氨基烯烃的对映体催化环加氢胺化反应中的适度性能遵循了sigma-amido插入机制中金属可及性的预期趋势。

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