![[(DPEPhos)(bcp)Cu]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)
アレンのPd触媒による酸化オーソ-C-HボリレーションによるアレンのPd触媒による酸化オーソ-C-Hボリレーション
1Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
Journal of the American Chemical Society
|December 14, 2011
まとめ
この研究は,N-アリルベンザミドのオーソ-C-Hボリル化のための新しいパラジウム触媒反応を導入しています. この方法は,改変された二ベンジリデネアセトン (dba) リガンドを使用し,様々な基板で良好な収量を達成します.
科学分野:
- 有機化学 オーガニック・ケミストリー
- カタリシス カタリシス カタリシス
- 合成方法論 合成方法論
背景:
- パラジウムによって触媒化されたC-H機能化は,有機合成の強力なツールです.
- 直接的なC-Hボリレーションのための効率的な方法の開発は,依然として活発な研究分野です.
- N-アリルベンザミドは,新しい合成変換を開発するための汎用的なプラットフォームを提供します.
研究 の 目的:
- パラジウム触媒による新型酸化オルト・C・Hボリレーション反応の発展を報告する.
- N-アリルベンザミドを用いたこの新しいボリレーション法の範囲と限界を調査する.
- 合成されたボリラ酸性製品の有用性を,さらなる合成用途で実証する.
主な方法:
- 改変されたダイベンジリデネアセトン (dba) リガンドを含むパラジウム触媒を使用した.
- 酸化性ボリレーションを促進するために,弱い塩基と強い酸化剤を使用します.
- ベンゾ酸から派生した一連の電子欠乏および電子豊富なN-アリルベンザミドとの反応を調査した.
主要な成果:
- N-アリルベンザミドの効率的なパラジウム触媒による酸化オートホー-C-Hボリレーションを達成しました.
- 修正されたdbaリガンド,弱い塩基,強力な酸化剤を含む,最適な収穫量を得るための重要な反応成分を特定しました.
- ベンザミド基板の多様な電子特性に対する耐性が実証されています.
- ボリラ化製品の変換を,その後の変換を通じて,様々な有価なシントンに示した.
結論:
- N-アリルベンザミドの新たなPd触媒によるオルトC-Hボリレーションを成功裏に開発した.
- この反応は頑丈で,ベンザミド誘導体の幅広い配列に適用できます.
- 生成されるボリル酸中介物質は,さらなる合成多様化のための多用途な構成要素として機能します.
関連する概念動画
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
02:36Regioselectivity 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.
01:11ortho–para-Directing Activators: –CH3, –OH, –NH2, –OCH3
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
03:08Hydroboration-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.
02:47Alkynes 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.
02:44Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.