ターミナルアルキンの非対称な反選択的ボリラルキル化
Chengmi Huang1, Dong Wu1, Yangyang Li1
1The Institute for Advanced Studies, Wuhan University, Wuhan, Hubei 430072, People's Republic of China.
Journal of the American Chemical Society
|August 15, 2023
まとめ
この研究は,アルキンから代替アルケンを生成するための新しいニッケル触媒反応を導入する. この方法は,価値あるエナチオ濃縮化合物への実用的な経路を提供して,3つの構成要素の結合において高い選択性を達成します.
科学分野:
- 有機化学
- カタリシス
- 非対称合成
背景:
- アルキンをアルケンに選択的に変換することは,代替アルケンの合成に不可欠である.
- 高い選択性を持つ多成分エナチオセレクティブ反応を達成することは,有機合成における重要な課題です.
研究 の 目的:
- ターミナルアルキンの非対称的反ステレオ選択性ボリルカルボ機能化を開発する.
- ニッケル触媒を用いた効率的な3つのコンポーネントのクロスカップリング反応を確立する.
主な方法:
- ターミナルアルキン,ディボロン反応体,およびプロキラルアルキル電ophilesのニッケル触媒化された三成分クロスカップリング.
- 選択性を制御するために安価なキラル・ダイアミン・リガンドを使用した.
主要な成果:
- ボリル炭水化物の機能化反応で高い地域性,ステレオ性,およびエナチオ選択性を達成した.
- α-ステロゲン中心を持つエナチオ濃縮アルケニルエステルへのアクセスのための効率的なプロトコルを開発した.
- 幅広い範囲と優れた機能群の互換性を証明した.
結論:
- 開発された方法は,複雑な分子を合成するための実用的で汎用的なアプローチを提供します.
- この反応は,ステレオレテント派生および薬物分子の合成に有用である.
関連する概念動画
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02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
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02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
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The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
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02:27Preparation of Alkynes: Alkylation Reaction
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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.
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02:36Regioselectivity and Stereochemistry of Hydroboration
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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...
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...
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02:42Acidity of 1-Alkynes
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The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.
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