フッ化物との複数の水素結合が触媒に与える影響:NMRスペクトロスコーピーの洞察
Francesco Ibba1, Gabriele Pupo1, Amber L Thompson1
1Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom.
Journal of the American Chemical Society
|November 9, 2020
まとめ
この研究では,核愛性フッ素化のためのBINAM由来ビスウレア触媒の水素結合を調査するためにNMRを使用しています. 最適化された触媒は安定したフッ素複合体を形成し,エナチオ選択性と相移転能力を高めます.
科学分野:
- カタリシス
- 有機化学
- 超分子化学
背景:
- 水素結合は触媒作用において極めて重要であり,複雑な化学的変換を可能にします.
- BINAM製ビスウレア触媒は,アルカリ金属フッ素を用いたエナンチオセレクティブな核性フッ素化を促進する.
- これらの触媒はフッ素源を溶解し,選択反応のためのキラル環境を作り出します.
研究 の 目的:
- NMR光学を用いて,BINAM由来ビスウレア触媒と溶液中のフッ素イオン間の水素結合ネットワークを解明する.
- これらの水素結合配列が核愛性化反応の効率とエナチオ選択性にどのように影響するかを理解する.
- フッ素複合化と触媒性能に対する触媒構造と対陽子の影響を調査する.
主な方法:
- 溶液中の水素結合相互作用を研究するために,H/F NMRスペクトロスコーピーを利用した.
- フッ化物への水素結合を定量化するために分析された診断結合定数 (1hJNH··F).
- 異なるフッ化物源 (例えば,TBAF,CsF) と二塩基メタンd2のカウンターイオンで触媒の振る舞いを調査した.
主要な成果:
- 13のビスウレア触媒のフッ化物に対する水素結合の数と強さを決定した.
- 非アルキル化触媒はエナチオセレクティブ性が低く,N-アルキル化触媒は硬直で三角形のフッ素複合体を形成することが観察された.
- フッ化物に対する3つの水素結合が触媒効果に不均等に寄与することを特定し,カウンターイオン効果も特徴づけられた.
結論:
- 触媒の構造は,核愛性フッ素化における水素結合ネットワークと触媒的結果に大きく影響する.
- ダイナミックに硬く,三角形の水素結合複合体は,効率的なエナチオ選択性フッ素供給の鍵です.
- 触媒の電子環境のチューニングは,相移転とエナチオ選択性を最適化するための戦略を提供します.
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