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Updated: Oct 17, 2025

Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators

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Published on: November 27, 2015

ケトンエノライゼーション用ナトリウムヘクサメチルジサイラジド:溶媒および基質依存性E-Z選択性および関連メカニズム

Ryan A Woltornist¹, 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

|October 13, 2021

まとめ

ナトリウムヘクサメチルジサイラジド (NaHMDS) 媒介によるケトンエノライゼーションは,E/ Z選択性に影響を与える,有意な溶媒および基板依存性を示す. 溶媒の影響は,聚合状態と反応運動を左右し,エノラート捕獲効率に影響する.

科学分野:

有機化学
物理化学
コンピュータ化学

背景:

ケトンエノライゼーションは有機合成における基本的な反応である.
エノライゼーションのステレオ化学的結果は,塩基,溶媒,添加物を含む反応条件によって影響を受けます.
選択性を制御するには,エノライゼーションのメカニズムを理解することが重要です.

研究の目的:

ナトリウムヘクサメチルジサイラジド (NaHMDS) を用いてケトンエノリゼーションの溶剤と基質依存性を調査する.
様々な溶媒におけるエノラートのメカニズム的経路と集積状態を解明する.
E/Zの選択性の理論的予測と実験的観測の関係を探求する.

主な方法:

溶媒の範囲でNaHMDSを用いた2メチル3ペンタノンのエノライゼーション (Et3N/トロール,MTBE,PMDTA/トロール,TMEDA/トロール,ディグライム,DME,THF).
Me3SiClとMe3SiOTfを用いたエノレート捕獲実験
反応速度と集積状態を決定するための運動研究.
密度関数理論 (DFT) の計算により,移行構造をモデル化し,選択性を予測する.

主要な成果:

異なった溶媒系において,E/Zエノ化選択性の有意な変化が観察された.
THFを除くほとんどの溶媒では,ステレオ化学的均衡が遅かった.
Me3SiOTfは迅速に反応し,Me3SiClは加熱または特定の条件を必要とする.
率の研究は,溶媒によって異なる結合状態 (モノマー,ジマー,自由イオン) を示した.
DFTの計算はE/Zの選択性についての洞察を提供したが,イオン断片の実験データとの相違はかなりあった.
基質を2メチルサイクロヘキサノンに変更することで,THFのトリソルバテドモノマーベースのエノリゼーションのメカニズムは根本的に変化しました.

結論:

溶媒の選択は,NaHMDS媒介によるケトンエノリゼーションのメカニズム,結合状態,およびステレオ選択性を決定する.
溶媒の調整,集積,および基板構造の相互作用がエノライゼーション経路を支配する.
現在の理論モデルは,特にイオン断片に関する実験結果を正確に予測する上で限界があります.

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