催化对甲基C-H键的特定区域化
Jaclyn M Murphy1, Joshua D Lawrence, Kazumori Kawamura
1Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, USA.
Journal of the American Chemical Society
|October 19, 2006
概括
催化剂使基中和的C-H键的区域特异性玻рили化成为可能. 这一过程有效地产生基酸盐,反应有利于受到阻碍最小的甲基组.
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.
- 有机合成 有机合成
背景情况:
- 选择性功能化C-H键仍然是有机化学的一个重大挑战.
- 催化反应为新型合成转化提供了潜力.
- 与烯相比,和碳化合物的玻里化研究较少.
研究的目的:
- 开发一种特定区域的方法,用于催化化的和终端C-H键.
- 调查影响基化区域选择性的固体和电子因素.
- 合成和表征-复合物作为潜在的催化剂前体.
主要方法:
- 使用各种和有机基质 (,胺,醇,醇) 催化的化反应.
- 对反应产物的分析以确定产量和区域选择性.
- 新型-玻利化合物的合成和X射线晶体学特征.
主要成果:
- 基酸盐通过和终端C-H键的区域特异性玻里化来合成高产量 (78-98%).
- 玻里化优先发生在最少受到固态阻碍和最缺电子的甲基组中.
- 基反应的产量高于基,与典型的有机金属C-H激活趋势形成鲜明对比.
结论:
- 已经建立了一种新且高效的催化化的和C-H键.
- 该反应表现出高的区域选择性,由硬体和电子因素控制.
- 合成的鲁-玻利尔复合物,包括一个具有桥接玻利尔连接体的复合物,显示出作为催化剂前体的前途.
相关概念视频
02:10Carbocations
Carbocations are one of the reaction intermediates formed during several nucleophilic substitutions or elimination reactions. A carbocation is an electron-deficient species with the central carbon atom having six electrons and three bonded atoms. The central carbon in a carbocation is sp2 hybridized with trigonal planar geometry. It has an empty p orbital perpendicular to the plane of the structure that can accept electrons. Thus, carbocations act as strong electrophiles and may react with any...
02:35Regioselectivity of Electrophilic Additions-Peroxide Effect
In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.
02:34Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
01:10Aldehydes and Ketones with HCN: Cyanohydrin Formation Mechanism
Cyanohydrins are formed when cyanide nucleophiles and carbonyl compounds like aldehydes and ketones react. A strong base, the cyanide ion, catalyzes cyanohydrin formation. The ions are generated from HCN under aqueous conditions. Once the cyanide ions are generated, the first step involves the nucleophilic attack of the cyanide ions on the electrophilic carbonyl carbon. This attack shifts the π electrons from the C=O to the oxygen atom forming the alkoxide ion intermediate. The alkoxide anion...
01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.