アルキニルアリルエーテルを選択的オーソC-H活性化による内部アルキンとパラジアム触媒化されたサイクル添加
Yasunori Minami1, Yuki Shiraishi, Kotomi Yamada
1Research and Development Initiative, Chuo University, Kasuga, Tokyo 112-8551, Japan. yminami@kc.chuo-u.ac.jp
Journal of the American Chemical Society
|March 30, 2012
まとめ
この研究では,アルキニルアリルエーテルが,パラジアム触媒によるオルトC-H活性化によって内部アルキンと反応して,2-メチリデン-2H-クロメネを代用して生成することを示し,汎用性の高い合成経路を示しています.
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活性化は,有機合成における強力なツールである.
- クロメネのようなヘテロサイクリック化合物を構築するための効率的な方法の開発は,大きな関心を持っています.
- グループ支援のC-H機能化の指示は,地域選択的な制御を提供します.
研究 の 目的:
- 置換された2-メチリデン-2H-クロメノンの新しい合成経路を開発する.
- 内部アルキネを持つアルキニルアリルエーサーのパラジウム触媒によるオーソC-H活性化のメカニズムを調査する.
- 開発された変換の範囲と機能グループ耐性を調査する.
主な方法:
- アルキニルアリルエーテルと内部アルキネの反応.
- 選択的オーソC-H活性化のためのパラジウム (((0) カタリストを使用します.
- 反応メカニズムを明らかにするためにデウテリウムマーキング実験を行いました.
主要な成果:
- 置換された2-メチリデン-2H-クロメンの効率的な合成が達成されました.
- アルキノキシ群は,オーソC-H機能化を効果的に導いた.
- 証拠によると,アリルパラジウムヒドリド複合体は重要な中間物質である.
- この反応は,幅広い機能群の許容性を示す.
結論:
- 2-メチリデネ-2H-クロメネを合成するための新しい効率的なパラジウム触媒法が確立されました.
- アルキノキシ群は,オルソC-H活性化のための効果的な指向群として機能します.
- 反応は,機械学的研究によって支持されているように,アリルパラジウム水素中介物を含む酸化添加を経由して進行します.
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関連する概念動画
Alkynes 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.
Reduction 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.
Preparation 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.
Electrophilic 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.
Electrophilic 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.
Cycloaddition Reactions: Overview
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.


