パラジウム触媒によるダイアステロセレクティブ sp3 C-H 結合活性化における反応性とステレオ選択性の理解:中間的特徴化と計算的研究
Ramesh Giri1, Yu Lan, Peng Liu
1Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
Journal of the American Chemical Society
|July 27, 2012
まとめ
この研究は,オクサゾリン誘導基を用いたPd (II) -触媒化C-H結合機能化における高い反応性とダイアステロ選択性を説明しています. 移行状態におけるステリック効果は,これらの重要な有機反応におけるステレオ化学的結果を決定する.
科学分野:
- 有機金属化学 有機金属化学
- カタリシス カタリシス カタリシス
- ステレオ化学 ステレオ化学
背景:
- オクサゾリン誘導のパラジウム触媒は,選択的なsp3 C-H機能化を可能にします.
- 高い反応性およびダイアステレオ選択性は,ヨウ素化およびアセトキシル化反応で観察されています.
研究 の 目的:
- オクサゾリン誘導 Pd (II) -触媒化 C-H 機能化の高反応性およびダイアステロ選択性の起源を調査する.
- C-Hの活性化と挿入のステップのメカニズムを解明する.
主な方法:
- キラルの中間物質のX線特性を含む実験的調査.
- 密度関数理論 (DFT) を用いた計算研究で,移行状態と中間を分析する.
- t-Bu-およびi-Pr-置換オクサゾリンに対する理論的予測と実験結果の比較.
主要な成果:
- 三核性キラルC-H挿入中間物質は,X線結晶学によって特徴づけられました.
- DFTの計算は,実験的反応性とダイアステレオ選択性を正確に予測しました.
- C-H活性化の最も安定した移行状態は,反ポジションの巨大なt-Buグループを含み,主要なダイアステロエーマーにつながります.
- C-H 結合と Pd-OAc 結合の間の最小二面角は,C-H 結合の割れには極めて重要です.
結論:
- この研究は,オクサゾリン誘導のC-H機能化における観察された立体化学的制御のメカニズム的説明を提供する.
- ステリック排斥と電子的要因は,C-H活性化経路とダイアステレオ選択性を支配する.
- DFT計算は,これらの触媒系における反応性を理解し予測するための貴重なツールです.
さらに関連する動画
関連する概念動画
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.
Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
Regioselectivity and Stereochemistry of Hydroboration
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Thermal Electrocyclic Reactions: Stereochemistry
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.

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