多个相邻的C-H键的电光催化氧化
Tao Shen1,2,3, Yi-Lun Li3, Ke-Yin Ye4
1Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, USA.
Nature
|December 6, 2022
概括
研究人员开发了一种新的电光催化方法,用于选择性C-H键氧化. 这种技术有效地将多个氧原子安装到分子中,避免多种应用的过氧化.
科学领域:
- 有机化学
- 催化剂
- 合成方法
背景情况:
- 含有氧的功能组在复杂的小分子中是必不可少的.
- 通过并发的C-H键氧化选择性安装具有挑战性,通常仅限于生物合成.
- 过度氧化是合成氧化反应的一个重大风险.
研究的目的:
- 开发一种用于选择性氧化两个或三个连续的C-H键的合成方法.
- 为了使简单的基或三乙转化为二或三基酸盐.
- 在没有破坏性过氧化的情况下实现选择性氧化.
主要方法:
- 使用电光催化,将光和电力结合起来驱动化学反应.
- 在精心控制的条件下使用强氧化催化剂.
- 研究了酸选择在指导选择性的作用.
主要成果:
- 成功实现了两个或三个连续的C-H键的选择性氧化.
- 证明了烯和三乙的转化为二氧化和三氧化.
- 通过明智的酸选择来控制氧化程度 (di- vs.
结论:
- 开发的电光催化方法为选择性C-H氧化提供了强大的新途径.
- 这种方法克服了同步C-H键功能化的过氧化挑战.
- 这种方法为合成有氧化有机分子提供了多功能工具.
相关概念视频
01:26Photochemical Electrocyclic Reactions: Stereochemistry
1.9K
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
1.9K
01:46Oxidative Cleavage of Alkenes: Ozonolysis
10.8K
In ozonolysis, ozone is used to cleave a carbon–carbon double bond to form aldehydes and ketones, or carboxylic acids, depending on the work-up.
Ozone is a symmetrical bent molecule stabilized by a resonance structure.
Ozone is a symmetrical bent molecule stabilized by a resonance structure.
10.8K
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
6.0K
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
6.0K
01:17Thermal Electrocyclic Reactions: Stereochemistry
2.1K
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
2.1K
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
2.4K
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
2.4K
01:21Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
4.0K
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...
4.0K