Cp2Zr(H) Clを用いてアミドをアルデヒドに軽度かつ選択的に水酸化する:範囲とメカニズムに関する洞察
Jared T Spletstoser1, Jonathan M White, Ashok Rao Tunoori
1Department of Medicinal Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, Kansas 66045-7582, USA.
Journal of the American Chemical Society
|February 24, 2007
まとめ
シュワルツ (Schwartz) とは
科学分野:
- 有機化学 オーガニック・ケミストリー
- 有機金属化学 有機金属化学
背景:
- アミド還元は,有機合成における基本的な変換である.
- 選択的および軽度の還元方法の開発は,複雑な分子合成に不可欠です.
研究 の 目的:
- アミド還元のためのCp2Zr(H) Cl (シュワルツの反応剤) の有効性を調査する.
- この変換の化学選択性と反応条件を調査する.
主な方法:
- シュワルツの反応剤を用いて,様々なアミド基板を還元した.
- 原子核磁気共振 (NMR) スペクトロスコーピーを用い,反応中介物質を研究した.
- 基板の選択性を決定する競争実験を実施した.
主要な成果:
- 温和な条件下でアルデヒドに,ワインレブのアミドを含む三次性アミドの還元で高い収量を達成した.
- エステルに対するアミドの化学選択性が実証されている.
- 安定した18電子ジルコナサイクルの中間物質を特定しました.
結論:
- Cp2Zr(H) Clは,アミドをアルデヒドに軽く選択的に還元するための非常に効果的な反応剤です.
- 反応はジルコナサイクルの中間体経由で進行し,選択性は窒素単一ペアの異地化によって影響を受けます.
- この方法は,有機化学におけるアルデヒド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
02:35Electrophilic Addition to Alkynes: Hydrohalogenation
Electrophilic addition of hydrogen halides, HX (X = Cl, Br or I) to alkenes forms alkyl halides as per Markovnikov's rule, where the hydrogen gets added to the less substituted carbon of the double bond. Hydrohalogenation of alkynes takes place in a similar manner, with the first addition of HX forming a vinyl halide and the second giving a geminal dihalide.
02:40Alkynes to Aldehydes and Ketones: Acid-Catalyzed Hydration
Introduction
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.
01:07Acid Halides to Amides: Aminolysis
Aminolysis is a nucleophilic acyl substitution reaction, where ammonia or amines act as nucleophiles to give the substitution product. Acid halides react with ammonia, primary amines, and secondary amines to yield primary, secondary, and tertiary amides, respectively.
In the first step of the aminolysis mechanism, the amine attacks the carbonyl carbon of the acyl chloride to form a tetrahedral intermediate. In the second step, the carbonyl group is re-formed with the elimination of a chloride...
In the first step of the aminolysis mechanism, the amine attacks the carbonyl carbon of the acyl chloride to form a tetrahedral intermediate. In the second step, the carbonyl group is re-formed with the elimination of a chloride...
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.
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...
01:10Aldehydes and Ketones with HCN: Cyanohydrin Formation Mechanism
Cyanohydrins are formed when cyanide nucleophiles and carbonyl compounds like aldehydes and ketones react. A strong base, the cyanide ion, catalyzes cyanohydrin formation. The ions are generated from HCN under aqueous conditions. Once the cyanide ions are generated, the first step involves the nucleophilic attack of the cyanide ions on the electrophilic carbonyl carbon. This attack shifts the π electrons from the C=O to the oxygen atom forming the alkoxide ion intermediate. The alkoxide anion...