检查排放的原子转移催化剂苏胺--的活性
Cheng Yang1, Luke A Farmer2, Derek A Pratt2
1Willard Henry Dow Laboratory, Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
Journal of the American Chemical Society
|April 26, 2024
概括
苏胺-N-oxyl (SINO) 与胺-N-oxyl (PINO) 相比,其作为原子转移 (HAT) 催化剂的性能优于电化学分析. 这一发现挑战了先前的评估,并强调了催化剂设计中的过渡状态两极分化的重要性.
科学领域:
- 有机化学
- 催化剂
- 电化学
背景情况:
- 胺-N-oxyl (PINO) 和相关的基因是C-H功能化的关键催化剂.
- 由于合成和评估的困难,开发超越PINO的优质N-oxyl催化剂是具有挑战性的.
- 目前的催化剂评估通常使用化学氧化剂,可能会掩盖真正的催化活性.
研究的目的:
- 通过电化学方法重新评估胺-N-oxyl (SINO) 作为原子转移 (HAT) 催化剂.
- 除了热力学考虑之外,了解影响N-oxyl HAT催化剂反应性的因素.
- 设计和描述新型,高反应性的N-oxyl HAT催化剂.
主要方法:
- 用潜在控制的电化学分析来评估催化剂.
- 对SINO和PINO HAT催化活性进行比较研究.
- 一种化SINO衍生物的合成和表征.
主要成果:
- 电化学分析表明SINO是一种比PINO更有效的HAT催化剂,这与之前的评估相矛盾.
- HAT催化剂的反应性受到热力学之外的因素的显著影响,例如过渡态极化.
- 一种新的化SINO衍生物成为迄今为止报告的最强大的N-oxyl HAT催化剂.
结论:
- 电化学评估可以更准确地评估N-oxyl HAT催化剂的性能.
- 过渡状态极化是设计高活性N-oxyl HAT催化剂的关键因素.
- 新开发的化SINO衍生物代表了C-H功能化催化学的重大进步.
相关概念视频
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
5.8K
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.
5.8K
02:25SN1 Reaction: Mechanism
11.8K
Kinetic studies of ionization of a tertiary halide in a protic solvent suggest that only the substrate participates in the rate-determining step (slow step). The nucleophile is involved only after the slowest step. The SN1 reaction takes place in a multiple-step mechanism.
Firstly, the haloalkane ionizes to generate a carbocation intermediate and a halide ion. This heterolytic cleavage is highly endothermic with large activation energy. The ionization of the substrate, facilitated by a...
Firstly, the haloalkane ionizes to generate a carbocation intermediate and a halide ion. This heterolytic cleavage is highly endothermic with large activation energy. The ionization of the substrate, facilitated by a...
11.8K
02:44Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
10.1K
Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
10.1K
02:26Preparation and Reactions of Sulfides
4.8K
Sulfides are the sulfur analog of ethers, just as thiols are the sulfur analog of alcohol. Like ethers, sulfides also consist of two hydrocarbon groups bonded to the central sulfur atom. Depending upon the type of groups present, sulfides can be symmetrical or asymmetrical. Symmetrical sulfides can be prepared via an SN2 reaction between 2 equivalents of an alkyl halide and one equivalent of sodium sulfide.
4.8K
01:29Preparation of Amines: Reduction of Oximes and Nitro Compounds
3.6K
Oximes can be reduced to primary amines using catalytic hydrogenation, hydride reduction, or sodium metal reduction. The reduction of aliphatic and aromatic nitro compounds to primary amines takes place by either catalytic hydrogenation or by using active metals like Fe, Zn, and Sn in the presence of an acid.
Though catalytic hydrogenation can reduce nitrobenzenes, the reduction is nonselective in the presence of other functional groups. For instance, if nitrobenzene contains an aldehyde group,...
Though catalytic hydrogenation can reduce nitrobenzenes, the reduction is nonselective in the presence of other functional groups. For instance, if nitrobenzene contains an aldehyde group,...
3.6K
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
3.3K
Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
3.3K