具有Co(III) 复合物的亚齐里丁的立体选择性识别:一种潜在的过渡状态模拟物,用于催化环氧化
Rhiana Bobb1, Gamil Alhakimi, Lisa Studniki
1Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.
Journal of the American Chemical Society
|April 25, 2002
概括
这项研究表明, (III) 复合物与联体有选择性地结合性亚齐里丁. (S,S) (III) 复合体表现出与阿齐里丁的结合更强,揭示了立体选择性识别机制.
科学领域:
- 协调化学 协调化学
- 立体选择性合成 立体选择性合成
- 有机金属化学 有机金属化学
背景情况:
- 奇拉尔亚齐里丁是有价值的合成中间体.
- 盐联体在不对称催化中被广泛使用.
- 了解立体选择性协调对于催化剂设计至关重要.
研究的目的:
- 为了研究合性亚齐里丁与 (III) 复合物的立体选择性协调.
- 阐明 (S,S) L-Co (III) 和 (R,R) L-Co (III) 复合物的结合偏好.
- 了解立体选择性识别的结构基础.
主要方法:
- 合成 (III) 复合物与联体.
- 1H NMR光谱测试以评估结合亲和力.
- 用X射线晶体学来确定协调结构.
- 用于结构分析的分子力学计算.
主要成果:
- 观察到1-(R) -phenyl-2-(S) -methylaziridine的可逆和立体选择性协调.
- 与 (R,R) L-Co(III) 复合物相比, (S,S) L-Co(III) 复合物与阿齐里丁结合的强度大约是 (R,R) L-Co(III) 复合物的三倍.
- 晶体结构揭示了阿齐里丁与 (III) 中心的精确协调模式.
结论:
- 这项研究表明,性亚齐里丁和 (III) - 盐复合物之间存在显著的立体选择性识别.
- 结构和计算数据为观察到的选择性提供了分子层面的理解.
- 这些发现有助于开发用于非对称合成的性催化剂.
相关概念视频
02:44Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
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.
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
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.
03:00Preparation of Epoxides
Overview
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
02:57Sharpless Epoxidation
The conversion of allylic alcohols into epoxides using the chiral catalyst was discovered by K. Barry Sharpless and is known as Sharpless epoxidation. The use of a chiral catalyst enables the formation of one enantiomer of the product in excess. This chiral catalyst is mainly a chiral complex of titanium tetraisopropoxide and tartrate ester (specific stereoisomer). The stereoisomer used in the chiral catalyst dictates the formation of the enantiomer of the product. In other words, the use of...
02:24Acid-Catalyzed Ring-Opening of Epoxides
Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...
02:26Base-Catalyzed Ring-Opening of Epoxides
Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...