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ヘクサデヒドロ・ダイエルス・アルダー・サイクロイソメリゼーション反応は,段階的なメカニズムで進行する

Tao Wang¹, Dawen Niu¹, Thomas R Hoye¹

¹Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States.

Journal of the American Chemical Society

|June 9, 2016

まとめ

ヘクサデヒドロ・ディエルス・アルダー反応は,段階的に進み,中間基を介して,協調的に進まない. 置換効果は電子を取り除く性質ではなく根幹の安定化を示しヘクサデヒドロ・ディエルス・アルダー反応性を決定する

科学分野:

有機化学
反応メカニズム
サイクル添加反応

背景:

ヘクサデヒドロ・ディエルス・アルダー反応 (HDDA) は,複雑なサイクルシステムを構築するための強力なツールです.
HDDAサイクロイソメリゼーションの正確なメカニズムを理解することは,その合成応用にとって極めて重要です.

研究の目的:

ヘクサデヒドロ・ディエルス・アルダー反応の段階的または協調的な性質を明らかにする.
HDDA反応速度とメカニズムに対する置換剤の影響を調査する.

主な方法:

異なるリモートアルキン置換剤 (R群) を含む一連のトラインHDDA基質の合成.
古典的なダイエルス-アルダー (DA) 反応のための類似のディエノフィルアルキンの準備.
HDDAサイクルとDAサイクル添加の両方の相対反応速度の測定.

主要な成果:

反応性の傾向は,R群による有意な差異を示した.
トリフローロメチル (CF3) 置換基質は最も遅いHDDAと最も速いDA反応を示した.
1- プロピニル置換基質は,最も速いHDDAと最も遅いDA反応を示した.

結論:

ヘクサデヒドロ-ディエルス-アルダー反応は,ダイラジカル中間物質を含む段階的なメカニズムによって進行する.
HDDAの反応性を支配する要因は,電子を取り除く効果ではなく,ラジカル安定化エネルギーである.

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