リチウムヘクサメチルジサイラジドによるケトンエノリゼーション:トライアキラミンの加速効果の構造と速度に関する研究
1Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14853-1301, USA.
Journal of the American Chemical Society
|November 20, 2003
まとめ
リチウムヘクサメチルジジラジライド (LiHMDS) の2メチルサイクロヘクサノンのエノリゼーションは,アミンによって加速されます. LiHMDSの集積および移行構造に対するアミンのステリック効果は反応速度を決定し,単純なステリック影響からの複雑な依存性を明らかにします.
科学分野:
- 有機化学 オーガニック・ケミストリー
- 反応メカニズム 反応メカニズム
- スペクトロスコーピーは,スペクトロスコーピーを用います.
背景:
- エノライゼーションは基本的な有機反応です.
- リチウムヘキサメチルジサイラジド (LiHMDS) は,強い非核愛基である.
- 塩基集積と溶解を理解することは,反応制御に不可欠です.
研究 の 目的:
- LiHMDSによって媒介される2メチルサイクロヘクサノンエノリゼーションのメカニズムを解明する.
- LiHMDSの集積と反応性に対するアミン添加物の影響を調査する.
- アミンの構造と濃度を反応運動学と相関させるため.
主な方法:
- 核磁共振 (NMR) スペクトロスコーピーは,LiHMDS/ケトン集積を研究する.
- 運動速度の研究のためのインシット赤外線 (IR) スペクトロスコーピー.
- アミンの構造と濃度の体系的な変化.
主要な成果:
- LiHMDSはトルーエンのケトン複合体ジマーを形成する.
- アミンは混合ジマーを形成し,ジマーベースの移行状態を経由してエノ化を加速する.
- アミンステリック障害は,集積,溶解,および速度加速に顕著な影響を及ぼします (>3000倍観察).
結論:
- エノライゼーション率は,LiHMDSの集積と移行状態の構造におけるアミン誘発の変化によって左右されます.
- 電子的効果ではなく,ステリック効果が,観察された複雑な速度依存性を支配しています.
- サブストラット・ベース・プレコンプレクセーションと混合集積は,反応性を媒介する上で重要な役割を果たします.
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