関連する実験動画
Updated: Jul 16, 2026
12:06
Synthesis of High Purity Nonsymmetric Dialkylphosphinic Acid Extractants
Published on: October 19, 2017
ディアルキルボロンブロミドを用いたタルト酸エセタルの開封:リング分裂から下流にステレオ選択性の証拠
Yvan Guindon1, William W Ogilvie, Josée Bordeleau
1Boehringer Ingelheim (Canada) Ltd., Bio-Méga Research Division, 2100 rue Cunard, Laval Québec, Canada H7S 2G5.
Journal of the American Chemical Society
|January 9, 2003
まとめ
この研究は,高度なダイアステロ選択性を持つ二次アルコールを合成するためにジョンソン型アセタルを用いた新しい方法を導入しています. このプロセスには,ルイス酸の参加と,効率的な合成のためのステレオ特異的変換が含まれています.
科学分野:
- 有機化学 オーガニック・ケミストリー
- アシンメトリック・シンセシス
背景:
- チラルの補助物質は,ステレオ選択的合成に不可欠である.
- ディメチルタルトラートは,多用途のキラルプールの出発材料です.
研究 の 目的:
- 二次アルコールの新しいダイアステロセレクティブ合成を開発する.
- ステレオ選択性誘導のメカニズムを解明する.
主な方法:
- アルデヒドとジメチルタルトラートからジョンソン型アセタルを調製する.
- リングはダイメチルボロンブロミド (Me2BBr) で開き,次いでクプラートが移動する.
- 結果となる二次アルコールの立体化学分析.
主要な成果:
- 二次アルコールの合成で高いダイアステロ選択性 (>30:1) を達成した.
- ルイス酸の参加とステレオ特異的なブロモアセタルの変換を含むメカニズムを提案した.
- SmI2還元またはメトオキシド処理による補助除去が実証されています.
結論:
- 開発された方法は,二次アルコールへの高度なダイアステレオセレクティブの経路を提供します.
- このメカニズムは,ルイス酸の役割と温度に依存するステレオスペシフィシティを強調しています.
- このアプローチは,非対称合成のための貴重なツールを提供します.
関連する概念動画
02:35Regioselectivity of Electrophilic Additions-Peroxide Effect
In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.
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.
01:57Preparation of Diols and Pinacol Rearrangement
Compounds bearing two hydroxyl groups are known as diols. When the hydroxyl groups are located on adjacent carbon atoms, the diols are called vicinal diols or glycols. Under acidic conditions, vicinal diols undergo a specific reaction called pinacol rearrangement.
The reaction begins with transferring a proton from the acid catalyst to one of the hydroxyl groups, producing an oxonium ion.
The reaction begins with transferring a proton from the acid catalyst to one of the hydroxyl groups, producing an oxonium ion.
02:24Acid-Catalyzed Ring-Opening of Epoxides
Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...
02:26Base-Catalyzed Ring-Opening of Epoxides
Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...
01:01Acid Halides to Carboxylic Acids: Hydrolysis
Hydrolysis of acid halides is a nucleophilic acyl substitution reaction in which acid halides react with water to give carboxylic acids. The reaction occurs readily and does not require acid or a base catalyst.
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic acid...
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic acid...