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ディフェニルプロリノールシリルエーテルでステレオ制御 触媒 マイケル添加:ステリックシールドまたはカートン・ハメットシナリオ?
Tamás Földes1, Ádám Madarász1, Ágnes Révész1
1Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences , Magyar tudósok körútja 2, H-1117 Budapest, Hungary.
Journal of the American Chemical Society
|November 2, 2017
まとめ
エナチオセレクティブ・アミン触媒は,しばしばステリック阻害によって説明される. この研究では,マイケルの反応におけるステレオ選択性はC−C結合形成によって制御され,反応速度はプロトネーションに依存し,既存のモデルに異議を唱える.
科学分野:
- 有機化学
- コンピュータ化学
- 反応メカニズム
背景:
- アミン触媒反応におけるエナチオ選択性は,通常,ステリックシールドモデルによって説明される.
- 最近の発見は,安定した下流の中間物質がステレオ制御に影響を与え,伝統的なステリック議論に挑戦することを示唆しています.
- Curtin-Hammettシナリオでは,反選択性は中間の安定性と反応性に関連している.
研究 の 目的:
- プロパナルとβ-ニトロチレン間の触媒ミカエル反応を計算的に調査する.
- ステレオ選択性モデルに関連するC−C結合形成とプロトネーションのステップを調べる.
- アミン触媒における反応速度とステレオ決定段階の関係を解明する.
主な方法:
- 密度関数理論 (DFT) の計算
- 反応経路の自由エネルギープロファイルの分析
- 実験データと質量スペクトロメトリの研究との計算結果の比較.
主要な成果:
- 速度決定段階 (プロトネーション) とステレオ決定段階 (C−C結合形成) は同一ではない.
- ステレオ選択性は主にC−C結合形成段階によって制御される.
- 計算結果は,前向きと裏向きの反応の選択性が一致しない実験観察結果と一致する.
結論:
- この研究は,C-C結合形成がステレオ選択性を制御し,陽子化が反応速度を決定する運動的スキームを提案している.
- これは,従来のステリックシールドと,アミン触媒によるエナンチオセレクティブ反応の単純なカルトン-ハメットモデルに異議を唱える.
- この発見は,複雑な触媒システムにおけるステレオ制御メカニズムの詳細な理解を提供します.
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