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Rh ((DPEPhos) -β-カルボニル置換アルデヒドを用いたカタライズされたアルキン水酸化:メカニズム洞察は,グラムスケールで選択的触媒を可能にする低触媒負荷につながる
James Barwick-Silk1, Simon Hardy2, Michael C Willis1
1Department of Chemistry, Chemistry Research Laboratories , University of Oxford , Mansfield Road , Oxford OX1 4TA , U.K.
Journal of the American Chemical Society
|May 16, 2018
まとめ
この研究では,ロジウム触媒を用いたβ-アミドアルデヒドの水酸化機構を詳細に説明しています. 触媒の負荷を下げると,アルキンサイクロトリメリゼーションよりも水酸化の選択性が向上する.
科学分野:
- 有機金属化学
- カタリシス
- 反応メカニズム
背景:
- 水酸化は炭素結合形成の重要な反応である.
- 反応メカニズムの理解は,触媒の最適化に不可欠です.
- サイクロトリメリゼーションのような競合する副作用は,製品の産出量と選択性を低下させる可能性があります.
研究 の 目的:
- β-アミドアルデヒドと1-オクチンのロジウム触媒化水酸化の詳細なメカニズムを解明する.
- 水酸化とアルキンのサイクロトリメリゼーション経路の相互作用を調査する.
- 反応条件を最適化して,高い選択性と,低触媒負荷での産出率を実現する.
主な方法:
- [Rh(cis-κ2-P,P-DPEPhos) ((アセトン) ]2[BArF4]ベースの触媒を用いた詳細なメカニズム研究
- 初期速度測定と運動同位体効果 (KIE) を含む運動研究
- 反応経路を追跡するための標識実験.
- 触媒の負荷と反応剤の濃度の体系的な変化
主要な成果:
- アチルヒドリド複合体は,水酸化過程における持続的な静止状態として識別される.
- β-アミドアルデヒドの四次置換はデカルボニレーションを阻害する.
- 移動式挿入は,ターンオーバーを制限し,選択性を決定するステップです.
- アルキンのサイクロトリメリゼーションは,アルデヒド濃度がゼロに近い場合にのみ競争力を持つ.
- 触媒の負荷を 20 mol% から 0.5 mol% に減らすと,選択性は 96% から ~ 100% に増加します.
結論:
- 反応メカニズムは,競合する水酸化とサイクロトリメリゼーション経路を含む.
- 触媒の負荷は,自由アルデヒドの可用性を制御することによって,選択性に重大な影響を及ぼします.
- 最適な条件により,水酸化製品のグラムスケール合成が,最小限の廃棄物で量的に可能になります.
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