アルケンの非金属光誘発C ((sp3) -Hボリル化
Chao Shu1, Adam Noble2, Varinder K Aggarwal3
1School of Chemistry, University of Bristol, Bristol, UK.
Nature
|October 29, 2020
まとめ
この研究では,新しい金属無C ((sp3) -Hボリレーション法が導入されています. 光誘導による水素原子移転を用いて,非反応性アルカンを有価なオルガノボロン反応剤に選択的に機能化します.
科学分野:
- 有機化学
- カタリシス
- 材料科学
背景:
- ボロン酸は医薬品,農薬,材料に不可欠です.
- 触媒性C-Hボリレーションにより,C-H結合の直接機能化が可能である.
- 伝統的な方法は貴金属を使用し,アロマティックC ((sp2) -HをアリファティックC ((sp3) -H結合よりも好む.
研究 の 目的:
- 金属のないC ((sp3) -Hボリレーション法を開発する.
- 非反応性アルカンの選択的機能化を実現する.
- 既定の金属触媒プロトコルと 選択性を比較する
主な方法:
- クロリド触媒による水素原子移転触媒を用いる.
- バイオレット光による電子移転.
- ホモリティックなC ((sp3) -H結合の割れがアルキル基を形成し,その後にボリル化が行われます.
主要な成果:
- 軽度な条件下で無金属C ((sp3) -Hボリレーションを達成する.
- 弱いものよりも強いメチルC-H結合に異常な選択性を示します.
- 塩素基-ボロン"アテ"複合体を特定し,ステリック選択性を決定する.
結論:
- この光誘導による水素原子移転戦略は,オルガノボロン化合物への新しい経路を提供します.
- 金属のないアプローチは,反応しないアルカンを有価な反応剤に変換します.
- 観測された選択性は,金属触媒によるボリル化に明確な代替手段を提供している.
![[DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59739.jpg&w=3840&q=50)
関連する概念動画
03:08Hydroboration-Oxidation of Alkenes
10.4K
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.
10.4K
01:26Radical Substitution: Hydrogenolysis of Alkyl Halides with Tributyltin Hydride
2.1K
Radical substitution reactions can be used to remove functional groups from molecules. The hydrogenolysis of alkyl halides is one such reaction, where the weak Sn–H bond in tributyltin hydride reacts with alkyl halides to form alkanes. Here, the reagent Bu3SnH yields tributyltin halide as a byproduct.
The bonds formed in this reaction are stronger than the bonds broken, making it energetically favorable. The reaction follows a radical chain mechanism similar to radical halogenation reactions,...
The bonds formed in this reaction are stronger than the bonds broken, making it energetically favorable. The reaction follows a radical chain mechanism similar to radical halogenation reactions,...
2.1K
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
20.1K
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.
20.1K
01:27Radical Substitution: Halogenation of Alkanes and Alkyl Substituents
9.5K
In the presence of heat or light, alkanes react with molecular halogens to form alkyl halides by a substitution reaction called radical halogenation. This reaction has three steps: initiation, propagation, and termination, as seen in the radical chlorination of methane to produce methyl chloride.
In the initiation step of the reaction, the chlorine molecule undergoes homolytic cleavage in the presence of light or heat, forming two highly reactive chlorine radicals. Propagation occurs in two...
In the initiation step of the reaction, the chlorine molecule undergoes homolytic cleavage in the presence of light or heat, forming two highly reactive chlorine radicals. Propagation occurs in two...
9.5K
02:36Regioselectivity and Stereochemistry of Hydroboration
9.2K
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.
9.2K
02:46Halogenation of Alkenes
17.9K
Halogenation is the addition of chlorine or bromine across the double bond in an alkene to yield a vicinal dihalide. The reaction occurs in the presence of inert and non-nucleophilic solvents, such as methylene chloride, chloroform, or carbon tetrachloride.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
17.9K