非对称的有机催化三组件1,3-双极循环添加:通过一种性布伦斯特德酸激活双极控制立体化学
Xiao-Hua Chen1, Wen-Quan Zhang, Liu-Zhu Gong
1Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemistry, University of Science and Technology of China, Hefei 230026, China.
Journal of the American Chemical Society
|April 5, 2008
概括
一种新型的双酸催化了三组分反应,有效地产生具有高反选择性的替代性罗利丁. 这种方法为合成复杂的性分子提供了一种温和而有效的途径.
科学领域:
- 有机化学 有机化学
- 不对称的催化剂.
- 合成方法论 合成方法论
背景情况:
- 三组分反应为复杂分子提供了高效的合成路径.
- 不对称的催化对于产生质纯化合物至关重要.
- 罗利丁支架在药品和天然产品中普遍存在.
研究的目的:
- 开发一种用于不对称的三组分反应的新型布伦斯特德酸催化剂.
- 为了合成具有高反选择性的多重置换型罗利丁.
- 为这种转化建立温和的反应条件.
主要方法:
- 作为催化剂,利用了从链接的BINOL中衍生出的新型双酸.
- 采用了涉及化物,氨基和双极的三组分反应.
- 优化反应参数,包括温度,溶剂和催化剂负载.
主要成果:
- 实现了多重替代型罗利丁的高产量.
- 产品表现出优异的抗选择性 (高 ee 值).
- 在温和的条件下,反应有效地进行.
结论:
- 开发的双酸是不对称的1,3-双极循环添加的有效催化剂.
- 这种方法提供了一个容易和enantioselective获取有价值的pyrrolidine衍生物.
- 温和的条件使这种方法对更广泛的合成应用具有吸引力.
相关概念视频
01:25Radical Anti-Markovnikov Addition to Alkenes: Overview
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl bromides.
02:36Regioselectivity and Stereochemistry of Hydroboration
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
01:28Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.
02:05Prochirality
The concept of prochirality leads to the nomenclature of the individual faces of a molecule and plays a crucial role in the enantioselective reaction. It is a concept where two or more achiral molecules react to produce chiral products. A typical process is the reaction of an achiral ketone to generate a chiral alcohol. Here, the achiral reactant reacts with an achiral reducing agent, sodium borohydride, to generate an equimolar mixture of the chiral enantiomers of the product. For example, an...
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.