从高旋转铁的imido复合体中催化C-H键氨基化
Evan R King1, Elisabeth T Hennessy, Theodore A Betley
1Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, USA.
Journal of the American Chemical Society
|March 17, 2011
概括
新的铁复合物与重的二甲基甲联体催化了C-H氨基化和烯酸亚化. 确定了一种高旋转铁 (III) imido基中间体,解释了这些反应中的催化活性.
科学领域:
- 有机金属化学 有机金属化学
- 催化剂是一种催化剂.
- 合成化学 合成化学
背景情况:
- 二甲基连接物是过渡金属复合体的多功能支架.
- 铁复合物越来越多地被探索为有机转换的催化剂.
- 了解反应机制,特别是涉及激素中间体的反应机制,对于催化剂设计至关重要.
研究的目的:
- 通过对硬质要求高的二甲基甲联体合成新型铁复合物.
- 研究这些复合物在C-H氨基化和氨酸亚齐里迪化中的催化活性.
- 阐明催化机制,包括确定关键中间体.
主要方法:
- 合成1,9-异位-5-美西二甲基连接物与重的基或基组.
- 使用NMR,X射线晶体学和莫斯巴尔光谱学等技术,制备和描述四坐标和三坐标铁复合体.
- 催化反应包括C-H氨基化和奥莱芬亚齐里丁化,包括动力学研究和同位素效应测量.
主要成果:
- 成功合成了三种新的二氧化甲配体及其相应的铁复合物.
- 隔离了一种独特的三坐标,高旋转铁复合体,其中有一个固态负载的基替代联结体.
- 在室温下在C-H氨基化 (12个基的回转率) 和olefin亚齐里丁化 (>85%转化为 styrene) 中表现出催化活性.
- 通过光谱数据和动态同位素效应 (12.8 ((5) 和 24 ((3)) 证实,确定了一种高旋转的Fe ((III) imido基中间体.
结论:
- 硬质要求高的二甲基甲基连接物使得不寻常的铁协调复合物的形成成为可能.
- 已分离的高旋转Fe (III) imido基被提议作为催化氨化和亚齐里丁化通路中的关键中间体.
- 这些铁像素复合物的独特电子结构有助于它们观察到的催化反应性.
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Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
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Various carboxylic acid derivatives (such as acid chlorides, esters, and anhydrides) can be used for the acylation of amines to yield amides. The reaction requires two equivalents of amines. The first amine molecule functions as a nucleophile and attacks the carbonyl carbon to produce a tetrahedral intermediate. This is followed by the loss of the leaving group and restoration of the C=O bond.
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The Hofmann and Curtius rearrangement reactions can be applied to synthesize primary amines from carboxylic acid derivatives such as amides and acyl azides. In the Hofmann rearrangement, a primary amide undergoes deprotonation in the presence of a base, followed by halogenation to generate an N-haloamide. A second proton abstraction produces a stabilized anionic species, which rearranges to an isocyanate intermediate via an alkyl group migration from the carbonyl carbon to the neighboring...


