对于不稳定的酸有一个通用的解决方案:从稳定的MIDA酸盐到空气稳定的缓释交叉合
David M Knapp1, Eric P Gillis, Martin D Burke
1Roger Adams Lab, Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Journal of the American Chemical Society
|May 2, 2009
概括
不稳定的酸现在可以储存和有效使用. 一种新方法将它们从稳定的MIDA酸盐中缓慢释放出来,使各种化学合成能够进行高效的交叉合反应.
科学领域:
- 有机化学 有机化学
- 合成化学 合成化学
- 药用化学 医学化学
背景情况:
- 许多有价值的酸衍生物,如2-异环,乙烯基和环类型,表现出固有的不稳定性.
- 这种不稳定性限制了它们在实验室环境中的实际用途,限制了桌面存储,并阻碍了有效参与交叉合反应.
研究的目的:
- 开发一种通用且强大的方法来克服各种酸衍生物的不稳定性.
- 为了将不稳定的酸转化为有机合成的耐用且易于使用的构建模块.
主要方法:
- 该研究引入了一种新的方法,涉及不稳定的酸在现场缓慢释放.
- 这种释放是从它们相应的N-甲基氨基酸 (MIDA) 酸前体中获得的,这些前体是稳定的.
主要成果:
- 开发的方法成功地稳定了三类以前不稳定的酸:2-异环,乙烯基和环衍生物.
- 这些稳定酸,在现场从MIDA酸盐生成,作为高效的构建模块.
- 它们表现出高效的交叉合能力与多种类型的化和化.
结论:
- MIDA 酸盐的 in situ 缓释策略为处理不稳定的酸提供了一个通用的解决方案.
- 这种方法显著提高了这些重要的合成中间体的可访问性和实用性.
- 该方法扩大了涉及具有挑战性的酸基质的交叉合反应的范围.
相关概念视频
Hydroboration-Oxidation of Alkenes
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.
Regioselectivity 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.
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
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.
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.
Crossed Aldol Reaction Using Weak Bases
This lesson deals with the crossed aldol reaction using weak bases. The self-condensation of an aldehyde having α hydrogen is prevented by adding it slowly to a mixture of formaldehyde and weak bases like hydroxide and alkoxide. Upon slow addition of the aldehyde, the base deprotonates the α carbon of the aldehyde to form the corresponding enolate. The enolate subsequently attacks the formaldehyde to form a single crossed product. Figure 1 depicts the aforementioned reaction.
Preparation of Alcohols via Addition Reactions
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...
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...
Alkylation of β-Diester Enolates: Malonic Ester Synthesis
Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.


