リチウムオポルザーエノラート:溶液構造,アルキル化機構,およびステレオ選択性の起源
Nathan M Lui1, Samantha N MacMillan1, David B Collum1
1Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca, New York 14853-1301, United States.
Journal of the American Chemical Society
|December 19, 2022
まとめ
オッポルザーエノラートは,溶媒と集積状態に影響されるメカニズムによってアルキル化されます. ステレオセレクティビティはスルタンリングから発生します.
科学分野:
- 有機化学
- ステレオ化学
- 物理有機化学
背景:
- カンフルスルタムベースのリチウムエノラートまたはオポルザーエノラートは,非対称合成において極めて重要です.
- ステレオ選択性を制御する鍵となるのは,それらの集積と反応性を理解することです.
- これまでの研究で 合成の有用性について調べましたが 機械的な詳細は不明です
研究 の 目的:
- オッポルザーエノラートのアルキル化メカニズムを解明する.
- これらの反応におけるステレオ選択性の起源を特定する.
- エノラート構造と反応性に対する溶媒と集積の影響を調査する.
主な方法:
- エノラート構造を決定するスペクトル分析と結晶分析.
- 反応メカニズムの探査のための運動研究.
- 密度関数理論 (DFT) を用いた計算モデリング.
- トロウエール,THF,HMPAでの溶媒依存性試験
主要な成果:
- サブストラットと溶媒によって異なる結合状態 (テトラメール,ジメール,モノメール) が観察された.
- HMPA (ヘクサメチルフォスフォラミド) の調整は,結合と反応性に影響する.
- アルキル化はHMPA溶解イオンペアを通して行われ,溶媒の効果は二次的である.
- 密度関数理論 (DFT) の計算は,ステレオ選択性がスラムリングのキラリティから生じるモデルをサポートする.
結論:
- オポルザーエノラートアルキル化のステレオ化学的結果は,スルタンリングの固有のキラリティによって決定される.
- ケレーションもリチウムカウンターイオンも,ステレオ選択性を制御する上で重要な役割を果たさない.
- 溶媒と集積状態は反応性を調節しますが,ステレオ制御の基本的な源ではありません.
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