フォスフォニウム塩における退化核性置換は,フォスフォニウム塩における退化核性置換である
Elizabeth V Jennings1, Kirill Nikitin, Yannick Ortin
1Centre for Synthesis and Chemical Biology, School of Chemistry and Chemical Biology, University College Dublin , Dublin 4, Ireland.
Journal of the American Chemical Society
|November 12, 2014
まとめ
ハロフォスフォニウムカチオンに対する退化ハリド置換は,ペンタコーディネート中間体を含む2段階のメカニズムによって発生します. 実験的および計算的研究は,この重要な化学反応に影響を与えるエネルギーバリアとステリック効果を明らかにしています.
科学分野:
- オーガノフォスファルス 化学 化学
- 反応メカニズム 反応メカニズム
- コンピューティング・ケミストリー
背景:
- テトラコーディネートハロフォスフォニウムカチオンに対する退化ハリド置換反応は,有機リン化学において根本的なものです.
- そのメカニズムとエネルギーバリアを理解することは,反応性を予測し,新しい合成経路を設計する上で極めて重要です.
研究 の 目的:
- ハロフォスフォニウムカチオンに対する変性ハリド置換のメカニズムを解明し,エネルギーバリアを決定する.
- 代用剤が反応速度とステレオ化学に及ぼす影響を調査する.
- 機械的洞察のための計算上の予測と実験的発見を比較する.
主な方法:
- 変化温度 (VT) と交換スペクトロスコピー (EXSY) 核磁気共振 (NMR) の技術が採用されました.
- 変性塩を分解するためにキラル置換剤 ((s) Bu) を利用した新しい実験設計.
- 反応システムをモデル化し,エネルギープロファイルを分析するために,計算化学のアプローチが開発されました.
主要な成果:
- バックサイド攻撃と解離を伴う2段階のメカニズムは,ペンタコーディネートディハロフォスフォラン中間物質を形成するために強く支持されました.
- 実験的に決定されたエネルギーバリアは,ベリーの擬似回転を除いて,<9からほぼ20kcalmol (−1) までの範囲であった.
- クロロロフォスフォニウム塩化物は,ペンタコーディネート中間物質のより容易なアクセシビリティのために,ブローム類比よりも低いエネルギーバリアを示した.
- 大量の置換物 (Me < Et < (i) Pr < (t) Bu) は反応を遅らせ,関連メカニズムとステリック障害と一致する.
- 溶液中のイオンペアの存在に起因する1次流動学が観察されました.
- もっと多くのO'Ferrall-Jencksプロットは,三角二ピラミッド中間物質の浅い潜在的な井戸を示した.
結論:
- この研究は,ハロフォスフォニウムカチオンに対する変性ハリド置換の2段階の関連メカニズムを確認した.
- エネルギーバリアは,ハリド同一性および置換物のステリック量によって影響を受けます.
- 計算および実験データは,反応経路と中間構造の包括的な理解を提供します.
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