同位体効果とロジウム触媒によるサイクロプロパナーションにおける選択性の性質
Daniel T Nowlan1, Timothy M Gregg, Huw M L Davies
1Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842, USA.
Journal of the American Chemical Society
|December 18, 2003
まとめ
ディロジウムテトラカルボキシラート触媒は,ロジウムカルベノイド中間体を通じたアルケンのサイクロプロパナーションを促進します. 動的同位体効果とDFT計算は,非同期的な移行状態を明らかにし,この重要な有機変異のカルベノイド機構を確認します.
科学分野:
- 有機金属化学 有機金属化学
- アシンメトリック・カタリシス
- 反応メカニズム研究 反応メカニズム研究
背景:
- ディロジウムテトラカルボキシラート複合体は,サイクロプロパネーション反応の触媒として広く使用されています.
- 移行状態の幾何学と中間物質を含む正確なメカニズムを理解することは,触媒の設計と最適化に不可欠です.
- 動的同位体効果と計算方法は,反応経路の解明のための強力なツールです.
研究 の 目的:
- 様々なダイアゾアセテートを使用したアルケンのジロジウムテトラカルボキシラートの催化サイクロプロパネーションのメカニズムを調査する.
- 移行状態の性質 (例えば,シンクロン対非シンクロン) を決定し,鍵となる中間を特定します.
- 密度関数理論 (DFT) の計算を,実験的な運動同位体効果データに対して検証するために.
主な方法:
- 異なるオレフィンの位置での炭素13の動性同位体効果 (KIEs) の測定.
- 密度関数理論 (DFT) の計算,特にB3LYP関数を使用しています.
- 提案されたメカニズムを検証するために,理論的に予測された値と実験的なKIEsの比較.
主要な成果:
- 大量の (13) C KIE は,高度に非同期的なサイクロプロパネーション移行状態を示します.
- 実験データと計算データは,ロジウムカルベノイド中間物質を含むメカニズムを強く支持しています.
- DFT計算は,反応障壁,ステレオ選択性,および反応性傾向を正確に予測し,理論モデルを検証します.
結論:
- サイクロプロパネーションのメカニズムは,ロジウムカルベノイドの形成を経て,その後,非同期的な協調した移行状態を経て進行します.
- チラルディロジウム触媒は,似たような移行状態の幾何学を維持し,ステレオ選択性に影響を与えます.
- Rh ((2) ((S-DOSP)) ((4) -触媒化されたサイクロプロパナーションにおけるエナチオ選択性の新しいモデルが提案されています.
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