ピリジンN酸化物 vs ピリジン基質 Rh ((III) 催化酸化C−H結合機能化
Sharon R Neufeldt1, Gonzalo Jiménez-Osés1, John R Huckins2
1†Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States.
Journal of the American Chemical Society
|July 22, 2015
まとめ
ピリジンのN酸化基質は,より強いRh相互作用により,Rh(III) 触媒による解消反応において,反応性とC(2) 部位選択性が強化されている. 計算による研究は,選択性に影響を与える異なる速度制限ステップと重要な相互作用を明らかにしています.
科学分野:
- 有機化学
- 有機金属化学
- コンピュータ化学
背景:
- ピリジン誘導体は,アルキンとRh (III) 触媒による無効反応を経験する.
- ピリジン基板は,N酸化物と比較して,反応速度が遅く,サイト選択性が低い (C(2) -H対C(4) -H).
- 基質の反応性と選択性を理解することは,合成アプリケーションにとって極めて重要です.
研究 の 目的:
- ピリジンN酸化物基板における高反応性および部位選択性の起源を計算的に調査する.
- ピリジンのN酸化物とピリジンの誘導体の反応機構をRh (III) 触媒式無効化で比較する.
- C-Hの活性化とアルキンの挿入ステップを制御する要因を解明する.
主な方法:
- 密度関数理論 (DFT) の計算を使用した.
- 反応経路,移行状態,エネルギーバリアを分析した.
- 運動同位体効果の研究とH/D交換実験は実験的検証を提供した.
主要な成果:
- ピリジンのN酸化物は,より強い指向群Rh相互作用により,より反応性がある.
- アルキンの挿入は,ダイアルキルアルキンのN酸化物を制限し,選択性を決定する.
- C-H活性化はピリジンのC(2) -機能化を制限し,アルキンの挿入はC(4) -機能化を制限する.
- N-オキシドの高いC2選択性は,協力的な電子とステリック効果から生じる.
- ピリジンの基板は,C ((2)) とC ((4) の機能化にほぼ同一のエネルギーバリアを示し,選択性が低下する.
結論:
- ピリジンN酸化物の反応性およびC2選択性の向上は,Rh触媒との良好な相互作用に起因する.
- C-Hの活性化とアルキンの挿入段階の相互作用は,全体的な反応性と選択性を決定する.
- 計算上の発見は実験的証拠によって支持され,反応機構の包括的な理解を提供します.
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