催化区域和选择性化三基替代以构建α-四度乳酸
在PubMed上查看摘要
概括
此摘要是机器生成的。一种新的Rh催化不对称的水合形成方法从具有挑战性的烯酸制造出奇拉性α-四度性乳酸. 这一突破为药物发现和材料科学提供了有效的合成.
科学领域
- 有机化学
- 不对称的催化
- 医学化学
背景情况
- 在药物发现和材料科学方面,开发对α-四元乳的立体选择方法至关重要.
- 在非对称的甲基化 (AHF) 反应中,三替代的甲基通常是不活性的.
- 凯勒曼的规则通常限制了AHF反应的范围.
研究的目的
- 开发一种新型立体选择性方法来合成α-四元乳酸盐.
- 为了克服AHF中三替代烯的惰性.
- 为了规避基勒曼规则所规定的限制.
主要方法
- 三替代烯的催化不对称化 (AHF).
- 使用特定的配体和反应条件来实现高选择性.
- 使用计算研究来阐明反应机制.
主要成果
- 成功合成了具有α-四分体立体中心的多种β-和γ-乳酸盐.
- 实现了特殊的区域和反选择性 (高达>20:1 rr,99% ee).
- 证明了广泛的基板范围,功能组耐受性,可扩展性和原子经济性.
结论
- 开发的Rh催化AHF是一种温和而高效的方法来获取有价值的性乳酸.
- 这种反应克服了重要的合成挑战,包括素惰性和凯勒曼法则.
- 计算洞察力表明特定的相互作用控制了选择性,为进一步的催化剂设计铺平了道路.
相关概念视频
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...
If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
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...
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
Borane as a reagent is very reactive, as the...
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.
The reaction proceeds with the slow protonation of an alkene by a hydronium ion to form a carbocation, which is the rate-determining step.
The reaction involving a tertiary carbocation intermediate is faster than a reaction proceeding through a secondary or primary carbocation. This can be justified by comparing their...
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
Mechanism
The hydroboration-oxidation reaction is a two-step...

