用铜催化,用基二甲酸取代二甲酸的反选择性基替代
Yoshinori Shido1, Mika Yoshida, Masahito Tanabe
1Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Japan.
Journal of the American Chemical Society
|October 31, 2012
概括
这项研究引入了使用基化合物进行的第一个催化酶选择性基替代. 这种新的方法有效地产生带有功能化的基群的奇拉性基,推进非对称合成.
科学领域:
- 有机化学 有机化学
- 不对称的合成方法
- 有机金属化学 有机金属化学
背景情况:
- 基替代反应是有机合成的基础.
- 开发用于创建奇拉中心的enantioselective方法至关重要.
- 基化合物具有独特的反应性,但在反选择性基替代中尚未得到充分研究.
研究的目的:
- 为了实现第一个利用基化合物的催化酶选择性基替代反应.
- 开发一种用于合成终端基因的协议,其立体中心与sp(3) - 基团分支.
- 建立一个有效的策略,以对奇拉性基基基基基基基基基基基基合成.
主要方法:
- 使用了基-9-BBN试剂和初级化.
- 采用一个铜(I) -DTBM-SEGPHOS催化系统.
- 研究了用γ-替代的化的反应.
主要成果:
- 在基替代中获得了优秀的γ-选择性和高的enantioselectivities.
- 成功制造出具有基立体中心的终端基,具有功能化的sp{3}-基团.
- 证明了一种有效的策略,用于α-类固醇性奇拉性基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基
结论:
- 开发的催化系统代表了用基试剂对基选择性基替代的突破.
- 这个协议提供了一条通往有价值的性构建块的多功能路线.
- 这些发现为合成具有高立体化学控制的复杂有机分子开辟了新的途径.
相关概念视频
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.
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In organic synthesis, the formation of products can be altered by changing the reaction conditions. For example, a dibromo addition product is formed when propene is treated with bromine at room temperature. In contrast, propene undergoes allylic substitution in non-polar solvents at high temperatures to give 3-bromopropene. In order to avoid the addition reaction, the bromine concentration must be kept as low as possible throughout the reaction. This can be achieved using N-bromosuccinimide...
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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.
α-Alkylation of Ketones via Enolate Ions
Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by resonance, and its hybrid structure exhibits negative charges on the carbonyl oxygen and the α carbon. This ambident nucleophile can attack an electrophile via two possible sites: the carbonyl oxygen, known as O-attack, or the α carbon, known as C-attack. The nucleophilic attack via the carbanionic site is preferred. This is due to the strong interaction...
Radical 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.


