マグネシウムビス ((ヘクサメチルジジラジル化) を媒介したケトンエノリゼーションの運動学とメカニズム)
Xuyang He1, J Jacob Morris, Bruce C Noll
1Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
Journal of the American Chemical Society
|October 13, 2006
まとめ
マグネシウムビス (hexamethyldisilazide) はプロピオフェノンと反応してエノラートを形成する. 鍵となる中間物質は,分子内プロトン移転を経験し,速度制限のステップでトンネリングが観察されます.
科学分野:
- 有機金属化学 有機金属化学
- 反応メカニズムの研究 反応メカニズムの研究
- 顕微鏡および結晶分析による分析
背景:
- ケトンエノ化のメカニズムを理解することは,有機合成において極めて重要です.
- マグネシウムアミド複合体は,デプロトネーション反応の効果的な基礎である.
- マグネシウム媒介反応における中間物質の役割は,詳細な調査を必要とする.
研究 の 目的:
- マグネシウムビス (hexamethyldisilazide) によって媒介されるプロピオフェノンエノリゼーションのメカニズムを解明する.
- 反応中間物質を特徴づけ,速度を制限するステップを決定する.
- 反応動力学における同位体置換の影響を調査する.
主な方法:
- プロピオフェノンとマグネシウムビス (hexamethyldisilazide) がトルーエンで反応する.
- 溶液NMR (1H,拡散順序によるNMR),UV対光譜,IR光譜,X線結晶学を用いた特徴付け.
- デウテリウムイソトープ効果測定や計算による調査を含む運動学的研究.
主要な成果:
- (E) -および (Z) -エノラート混合物の形成, [ ((HMDS) ((2) MG ((2) mu-HMDS) { mu-OC ((Ph) = CHCH ((3))) ].
- 三座標モノメア中間物質 (HMDS) の識別と特徴付け, (Mg{eta}1) -O=C{Ph}CH{2) CH{3) }である.
- 速度の制限段階として確認された陽子伝達は,主要なデュテリウム運動同位体効果 (k ⋅ H ⋅ k ⋅ D = 18.9) とトンネリングの証拠が顕著である.
結論:
- エノライゼーションは,分子内プロトン移転を含む単一の中間体を通じて行われます.
- 量子力学的トンネリングは,環境温度での反応速度に大きく貢献します.
- この研究は,マグネシウムアミドが促進するケトンエノライゼーションの詳細なメカニズム的な洞察を提供します.
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