アルファ,ベータ不飽和チオアミドに端末アルキンの直接触媒非対称結合添加
Ryo Yazaki1, Naoya Kumagai, Masakatsu Shibasaki
1Institute of Microbial Chemistry, Tokyo, 3-14-23 Kamiosaki, Shinagawa-ku, Tokyo 141-0021, Japan.
Journal of the American Chemical Society
|July 29, 2010
まとめ
この研究は,チオアミドのエナチオセレクティブアルキニレーションを生み出すための新しい触媒的方法を導入しています. このアプローチは,価値あるβ-アルキニルチオアミドの効率的な合成のために協力的触媒を使用します.
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・カタリシス
- 合成方法論 合成方法論
背景:
- 結合添加反応は,有機合成において根本的なものです.
- 不飽和化合物を機能化するためのエナチオセレクティブの方法の開発は,依然として重要な課題です.
- チオアミドは独特の反応性を持っていますが,非対称的結合添加ではあまり探求されていません.
研究 の 目的:
- アルファ,ベータ不飽和チオアミドに端末アルキンの直接触媒非対称結合添加を開発する.
- ベータ-アルキニルチオアミドの形成において高いエナンチオ選択性を達成する.
- 結果となる製品の合成的有用性を探求する.
主な方法:
- 柔らかいルイス酸/硬いブロンステッド塩基の協同触媒を用いた.
- 反応のためにプロトン伝送条件を採用した.
- 制御実験を通じて反応メカニズムを調査した.
主要な成果:
- アルファ,ベータ不飽和チオアミドに端末アルキンの直接触媒的非対称結合添加を達成した.
- ベータ-アルキニルチオアミドの合成において高いエナチオ選択性を示した.
- 銅チオアミドエノラートを,ブレンステッド塩基として作用する重要な中間物質として特定した.
結論:
- 協同触媒は,アルキンとチオアミドの同時活性化を可能にします.
- プロトンの移転は,触媒サイクルを駆動するために不可欠です.
- アルキニル化製品は,合成の有用性を示し,異なった変換可能性を露呈する.
関連する概念動画
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.
01:09Conjugate Addition to α,β-Unsaturated Carbonyl Compounds
α,β-Unsaturated carbonyl compounds are molecules bearing a carbonyl and alkene functionality in conjugation with each other. The conjugation in the molecule leads to three resonance structures. The hybrid form exhibits two probable electrophilic sites: the carbonyl carbon and the β carbon.
02:27Preparation of Alkynes: Alkylation Reaction
Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
01:27Conjugate Addition (1,4-Addition) vs Direct Addition (1,2-Addition)
α,β-Unsaturated carbonyl compounds with two electrophilic sites, the carbonyl carbon, and the β carbon, are susceptible to nucleophilic attack via two modes: conjugate or 1,4-addition and direct or 1,2-addition.
Conjugate addition results in a thermodynamically stable product. The reaction retains the stronger C=O bond at the expense of the weaker C=C π bond. The process is slow as the β carbon is less electrophilic than the carbonyl carbon.
Direct addition products are formed faster owing to...
Conjugate addition results in a thermodynamically stable product. The reaction retains the stronger C=O bond at the expense of the weaker C=C π bond. The process is slow as the β carbon is less electrophilic than the carbonyl carbon.
Direct addition products are formed faster owing to...
02:38Electrophilic Addition to Alkynes: Halogenation
Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.