ボロンから炭素への急進的なアリル移動
Dinghai Wang1, Christian Mück-Lichtenfeld1, Constantin G Daniliuc1
1Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstraße 40, 48149 Münster, Germany.
Journal of the American Chemical Society
|June 21, 2021
まとめ
この研究は,新しい有機変換である,アリルボロナート複合体における,ボロンから炭素への根源的な1,5アリル移行を導入する. この方法により,高度なダイアステレオ選択性を有する温和な条件下での多様なアリレート製品にアクセスできます.
科学分野:
- 有機化学
- 激進 的 な 反応
- オーガノボロン化学
背景:
- アリル基の移動は,アリル基の移動を含む有機的変換として知られています.
- 以前の研究では N,O,Si,P,S,Sn,Ge,Seなどの元素が 移動していることが報告されています
- ボロン中心からの過激なアリル移動は以前には記録されていません.
研究 の 目的:
- ボロンから炭素への原始的1,5アリル移動に関する最初の報告を提出する.
- 関連製品を合成する際にこの反応の有用性を実証する.
- この新しい変容の範囲とメカニズムを探求する.
主な方法:
- アルケニル・アリル・ボロナート複合体へのラジカル添加による炭素中心のラジカルの生成.
- ボールから炭素への1,5アリル移行の調査.
- アルケニルボロン酸エステルとアリルリチウム反応剤からボロナート複合体の局所生成
- 提案されたメカニズムをサポートするためにDFT計算を使用します.
主要な成果:
- ボロンから炭素への 1,5-アリル基の移行を成功裏に実証した.
- 高いダイアステロ選択性を持つ4アルキルボロンエステルの合成
- アリル分子を変化させることで 分散合成を容易にする.
- 類似の1,4-アリルシフトの実現可能性
結論:
- ボロンからのラジカル1,5アリル移行は,新しい効率的な合成方法論です.
- この反応は,様々なアリレートされたアルキルボロンエステルへの多用途の経路を提供する.
- 発見は,既知の根性アリル移動反応の範囲を拡大する.
関連する概念動画
03:08Hydroboration-Oxidation of Alkenes
9.6K
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.
9.6K
01:07Radicals: Electronic Structure and Geometry
4.5K
This lesson delves into the geometry of a radical, which is influenced by the electronic structure of the molecule. The principle is similar to that of a lone pair, where the unpaired electron influences the geometry at the radical center.
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
4.5K
01:27Radical Substitution: Allylic Bromination
5.9K
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...
5.9K
00:47Radical Formation: Addition
2.0K
Radicals can be formed by adding a radical to a spin-paired molecule. This is typically observed with unsaturated species, where the addition of a radical across the π bond leads to the production of a new radical by dissolving the π bond. For example, the addition of a Br radical to an alkene yields a carbon-centered radical.
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an...
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an...
2.0K
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
19.4K
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.
19.4K
02:36Regioselectivity and Stereochemistry of Hydroboration
8.7K
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.
8.7K