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フォスフィン結合アルキルパラジウムからの還元性除去 (II) アミド複合体から sp³ 炭素-窒素結合を形成する

D Matthew Peacock¹, Quan Jiang², Patrick S Hanley¹

¹Department of Chemistry , University of California , Berkeley , California 94720 , United States.

Journal of the American Chemical Society

|March 15, 2018

まとめ

研究者らは,リン酸塩と結合したアルキルパラジウム (II) アミド複合体を調査し,リガンド特性がアルキル-窒素結合を形成するための還元性除去率に著しく影響することを発見した. ステリカルに阻害されたまたは電子が少ないリガンドは反応を遅らせます.

科学分野:

有機金属化学
カタリシス
反応メカニズム

背景:

パラジウム触媒によるクロスカップリング反応は有機合成において極めて重要です.
効率的な触媒システムの設計には還元性除去の理解が重要です
パラジウム複合体からの還元性除去によるアルキル-窒素結合形成は重要な変換である.

研究の目的:

フォスフィン結合アルキルパラジウム (II) アミド複合体の形成を調査する.
還元性排除反応の速度を制御する要因を決定する.
還元性排除における異なるリガンドシステムの反応性を比較する.

主な方法:

フォスフィン結合アルキルパラジウム (II) アミド複合体の合成
反応速度を測定するための実験的運動研究.
反応経路とエネルギーバリアを解明するための計算式 (DFT) 研究.
アニリドとフォスフィンリガンドの電子およびステリック特性が異なる.

主要な成果:

t-Bu3P結合複合体からの還元性排除は,NHC結合複合体と比較してより低い自由エネルギーバリアを示した.
反応速度は,電子が少ないか,ステリックに阻害されたアニリドリガンドで減少した.
P,O リガンドを持つ4座標複合体は,3座標複合体よりも減速性排除を示した.
P,O リガンドの柔軟なリンクは,リガンド解離を可能にすることで,より迅速な還元性排除を容易にした.

結論:

リガンド・エレクトロニクスとステリックは,還元性排除の速度を決定的に影響する.
3座標のパラジウム複合体は,一般的に4座標の複合体よりも反応性が高い.
柔軟なP,Oリガンドは,Pd-O結合の延長または解離を含む協調したメカニズムを通じて,還元性の除去率を高めることができます.

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