离子催化完全化西兰的代基化
Tao He1, Hendrik F T Klare2, Martin Oestreich3
1Institut für Chemie, Technische Universität Berlin, Berlin, Germany.
Nature
|October 11, 2023
概括
化学家开发了一种新的方法来功能化化合物,将简单的基转化为有价值的衍生物. 这种创新的化反应为合成复杂的有机分子提供了一种多功能途径.
科学领域:
- 有机化学
- 合成有机化学
背景情况:
- 碳化合物或有机在现代化学中至关重要,但它们的选择性合成,特别是功能化和替代,仍然具有挑战性.
- 传统方法通常从基开始,导致复杂的分离问题,完全化基 (四级基) 通常被认为是无反应的合成中间体.
研究的目的:
- 引入一种新的,高效的方法,用于从易于获得的四级中合成功能化的有机化合物.
- 展示一种多功能"自上而下的"方法,克服现有的"自下而上的"合成策略的局限性.
主要方法:
- 离子催化代基化反应的发展.
- 使用基化物作为化物来源和基作为共同溶剂,它们也通过弗里德尔-克拉夫特化再生催化剂.
- 离子作为布伦斯特德酸来促进原代基化步骤.
主要成果:
- 成功地将四甲基 (Me4Si) 和相关的四级转化为多种功能化有机衍生物.
- 展示了含有的药物前体的合成,强调了该方法的实用性.
- 实现了三甲基 (Me3Si) 基的化学选择性甲基化,为Tamao-Fleming类型的酒精形成提供了途径.
结论:
- 开发的基化方法为传统的有机合成提供了有效和多功能替代方案.
- 这种"自上而下的"方法在合成可访问性和前体利用方面具有显著的优势,特别是对于复杂的分子.
- 该方法为制备功能化开辟了新的途径,包括那些与制药应用和基于的材料相关的途径.
相关概念视频
02:34Preparation of Alkynes: Dehydrohalogenation
15.9K
Introduction
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ammonia. The reaction proceeds with the loss of two equivalents of hydrogen halide (HX) via two successive E2 elimination reactions.
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ammonia. The reaction proceeds with the loss of two equivalents of hydrogen halide (HX) via two successive E2 elimination reactions.
15.9K
02:38Electrophilic Addition to Alkynes: Halogenation
8.3K
Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
8.3K
01:21Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
3.8K
By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
3.8K
01:10α-Alkylation of Ketones via Enolate Ions
3.1K
Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by resonance, and its hybrid structure exhibits negative charges on the carbonyl oxygen and the α carbon. This ambident nucleophile can attack an electrophile via two possible sites: the carbonyl oxygen, known as O-attack, or the α carbon, known as C-attack. The nucleophilic attack via the carbanionic site is preferred. This is due to the...
3.1K
02:27Preparation of Alkynes: Alkylation Reaction
10.2K
Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
10.2K
01:33Carboxylic Acids to Methylesters: Alkylation using Diazomethane
2.2K
Carboxylic acids react with diazomethane in an ether solvent via alkylation at the carboxylate oxygen atom to give methyl esters of the corresponding acid with excellent yields.
2.2K