POLAR EFFECTS IN FREE-RADICAL REACTIONS - HOMOLYTIC AROMATIC AMINATION BY THE AMINO RADICAL CATION, .+NH3 - REACTIVITY AND SELECTIVITY
POLAR EFFECTS IN FREE-RADICAL REACTIONS - HOMOLYTIC AROMATIC AMINATION BY THE AMINO RADICAL CATION, .+NH3 - REACTIVITY AND SELECTIVITY
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DOI：
10.1021/jo00197a030
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发表时间：
1984-01-01
影响因子：
3.6
通讯作者：
VENTURA, S
中科院分区：
文献类型：
--
作者：
CITTERIO, A;GENTILE, A;VENTURA, S
因此，为了最大限度地减少这些竞争过程，我们使用了溶剂乙酸，由于极性原因，对+ NH3的反应性较低，并且使用了足以维持先前研究3中均裂胺化（方案I）中已经建议的氧化还原链的最少量的Fe（II）盐。实际上，在这些条件下，使用未活化的芳香族底物也获得了令人满意的胺化产率，而使用失活的底物，产率较低，但仍然很重要。值得注意的是，该反应仅用极少量的 Fe (II) 盐 (< 1%) 即可发生。在Fe(II)盐的0.5-5%范围内，芳香胺化的产率实际上没有变化，而反应速率随着Fe(II)盐的量的增加而增加。在较高的 Fe (II)/HSA 比率下，速率进一步增加，但胺化产率降低，因为方案 I 链的终止步骤 (eq 5) 变得更加重要。在没有Fe(II)盐的情况下，在相同的条件下，不发生胺化反应。因此，方案I的链显得相当长；因此，基于 HSA 的产量低于定量，必须归因于竞争性方程式 6，因为溶剂无法形成氧化还原链。不能排除的另一种建议是水解产生的一些羟胺（式 6）与 HSA 反应，产生还原物质，例如 NH= NH，这有助于通过将 Fe (III) 转化为 Fe (II) 盐来维持方案 I 的链。通过在所有情况下使用进行了定量研究
Thus in order to minimize these competitive processes we have used a solvent, acetic acid, less reactive toward•+ NH3 for polar reasons and the smallest amount of Fe (II) salt sufficient to sustain the redox chain already suggested in the previous studies3 for the homolytic amination (Scheme I). Actually, under these conditions, satisfactory amination yields were obtained also with unactivated aromatic substrates, whereas with deactived substrates the yields were lower but still significant. The remarkable fact is that the reaction takes place with a very small amount of Fe (II) salt (< 1%). The yields of aromatic amination are practically unchanged in the range of 0.5-5% of Fe (II) salt, whereas the reaction rate increases with the amount of Fe (II) salt. At higher Fe (II)/HSA ratios the rate further increases, but the yields of amination decrease because the termination step (eq 5) of the chain of Scheme I becomes more important. In the absence of Fe (II) salt, under the same conditions, no amination re-action occurs.Thus it would appear that the chains of Scheme I are rather long; the yields less than quantitative, based on HSA, must be therefore ascribed to the competitive eq 6 because the solvent cannot contribute to a redox chain. An alternate proposal that cannot be excluded is some hy-droxylamine from hydrolysis (eq 6), reacts with HSA, producing a reducing species, such as NH= NH, which contributes to sustain the chain of the Scheme I by transforming Fe (III) to Fe (II) salt. A quantitative study was carried out by using in all cases