ケトンとリチウムヘクサメチルジジラジラジドの反応:競争的なエノリゼーションと1,2-添加
Pinjing Zhao1, Anthony Condo, Ivan Keresztes
1Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
Journal of the American Chemical Society
|March 12, 2004
まとめ
溶媒は,2-メチルサイクロヘクサノンがリチウムヘクサメチルジジラジル化物 (LiHMDS) とどのように反応するかに影響します. 溶媒によって,LiHMDSはエノライゼーションまたは1,2-添加反応を促進します.
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:
- リチウムヘキサメチルジサイラジド (LiHMDS) は,有機合成で一般的に使用される強い非核性塩基です.
- LiHMDSを含む反応の化学選択性は,溶媒の選択と反応条件によって影響を受けます.
- これらの影響を理解することは,合成結果を制御するために非常に重要です.
研究 の 目的:
- LiHMDS.と2メチルサイクロヘキサノンの反応の溶媒依存化学選択性を調査する.
- これらの変換に関与する反応経路と中間物質の解明.
- 異なる反応結果の間の分割の運動制御を決定する.
主な方法:
- 速度研究のためのインシット赤外線 (IR) スペクトロスコピー.
- 構造の解明のために,核磁共振 (NMR) スペクトロスコーピ ((6) Li, (15) N,および (13) C) を使用する.
- 反応経路を分析するための運動学的研究.
主要な成果:
- THF/トルーエンの場合,LiHMDSはエノ化を促進し,反応速度はTHF濃度に依存し,モノマーベースの経路を経由します.
- ピロリジン/トロウエンの場合,LiHMDSは1,2添加のみを生成し,アルファアミノアルコキシド-LiHMDS混合ジマーを形成する.
- ダイマーは,高度なNMR技術によって特徴づけられるコンフォームのペアとして存在します.
- 運動学的研究は,1,2-加法経路のためのモノマーベースの移行構造を示唆しています.
結論:
- 反応結果 (エノライゼーション対1,2加法) は,溶媒システムによって決定されます.
- 反応経路は濃度に依存し,両方の観察例では単体種を介して進行します.
- 観察された化学選択性は運動制御下にあるため,合成結果の指示において反応条件の重要性を強調しています.
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