通过激活实现对酸的分子间激素添加
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在PubMed上查看摘要
概括
此摘要是机器生成的。研究人员开发了一种使用可见光和激活来添加碳基的新方法. 这种方法在温和,无金属条件下有效合成多种乳酸盐和制药前体.
科学领域
- 有机化学
- 合成化学
- 摄影化学
背景情况
- 由于醇基碎片化,对碳基的分子间激素添加具有挑战性.
- 通过激素添加基来构建四元碳中心仍然是一个合成障碍.
研究的目的
- 开发一种可见光诱导的新方法,用于分子间激素添加到α-酸中.
- 能够合成各种乳酸盐和制药前体.
主要方法
- 可见光光还原催化与易斯酸激活相结合
- 使用基酸作为激素前体.
- 在现场形成复合物以稳定中间体.
主要成果
- 在可见光下成功将分子间基酸添加到α-酸中
- 在室温下合成多种替代乳酸盐.
- 在无金属流条件下证明了制药前体合成的可扩展性.
结论
- 激活策略克服了对碳酸的激进添加的挑战.
- 这种方法提供了一种温和,高效和可扩展的途径,
- 这种方法是多用途的,适用于各种基前体.
相关概念视频
Overview
The acid-catalyzed addition of water to the double bond of alkenes is a large-scale industrial method used to synthesize low-molecular-weight alcohols. An acidic atmosphere is required to allow the hydrogen in the water molecule to act as an electrophile and attack the double bond in an alkene. The addition of a proton to the double bond creates a carbocation intermediate. The proton preferentially bonds to the less substituted end of the double bond to create a more stable carbocation...
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...
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...
The reaction of hydrogen bromide with alkenes in the presence of hydroperoxides or peroxides proceeds via anti-Markovnikov addition. The radical chain reaction comprises initiation, propagation, and termination steps.
The mechanism starts with chain initiation, which involves two steps. In the first chain initiation step, a weak peroxide bond is homolytically cleaved upon mild heating to form two alkoxy radicals. In the second initiation step, a hydrogen atom is abstracted by the alkoxy...
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.
The observed...
The aldol reaction of a ketone under acidic conditions successfully forms an unsaturated carbonyl as the final product instead of an aldol. The acid-catalyzed aldol reaction is depicted in Figure 1.
Figure 1. The acid-catalyzed aldol addition reaction of ketones.
First, as shown in Figure 2, the acid protonates the ketone molecule to form the protonated ketone. The conjugate base of the acid deprotonates the α carbon of the protonated ketone to form the enol.
Figure 2. Formation of the enol.