末端アルキンのマルコヴニコフニコフ選択型分子間ヒドロチオレーションの触媒としてのオルガノジルコニウム複合体:範囲とメカニズム
Charles J Weiss1, Tobin J Marks
1Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
Journal of the American Chemical Society
|July 13, 2010
まとめ
オルガノジルコニウム (IV) 触媒は,アルキンがチオールで分子間ヒドロチオル化を効率的に媒介し,高マルコヴニコフ選択性と収穫率を達成します. ラジカル経路は抑制され,運動学的研究は,速度を制限するステップとしてZr-SR結合にアルキンの挿入を明らかにします.
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
- オーガニック・シンセシス オーガニック・シンセシス
背景:
- アルキンのヒドロチオレーションは,有機硫黄化合物を合成するための重要な反応です.
- 効率的で選択的な触媒システムの開発は,ヒドロチオレーションのための活発な研究分野であり続けています.
研究 の 目的:
- 末端アルキンの効率的で選択的なオルゴンジルコニウム (((IV) 媒介の分子間ヒドロチオレーションを報告する.
- 様々なオルゴジルコニウム前触媒を用いて反応機構,選択性,範囲を調査する.
主な方法:
- 使用されたCGCZrMe,Cp*ZrBn,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl,Cp*ZrCl
- 動力学的研究,デウテリウムラベリング,アクティベーションパラメータ測定を行いました.
- ラジカル阻害剤の効果を調査し,反応中間物質を分析した.
主要な成果:
- 高マルコヴニコフ選択性 (最大99%) と,様々なチオールによる末端アルキンの水素溶解で高収量 (>90%) を達成した.
- 72%の単離収量と99%のマルコヴニコフの選択性を有する準備的スケール合成が実証されました.
- ターンオーバーを制限するステップとして,Zr-SR結合にアルキンを挿入し,チオール誘発のZr-Cプロトノリシスが続くことを特定しました.
結論:
- オルガノジルコニウム (IV) 前触媒は,選択的分子間ヒドロチオレーションに非常に効果的です.
- 反応は,アルキンの挿入とプロトノリシスを含むメカニズムを通じて進行し,二次触媒の静止状態の可能性があります.
- 根本的な経路は抑制され,高マルコヴニコフの選択性を確保することができます.
関連する概念動画
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
Electrophilic Addition to Alkynes: Hydrohalogenation
Electrophilic addition of hydrogen halides, HX (X = Cl, Br or I) to alkenes forms alkyl halides as per Markovnikov's rule, where the hydrogen gets added to the less substituted carbon of the double bond. Hydrohalogenation of alkynes takes place in a similar manner, with the first addition of HX forming a vinyl halide and the second giving a geminal dihalide.
Alkynes to Aldehydes and Ketones: Acid-Catalyzed Hydration
Introduction
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.
Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Radical Anti-Markovnikov Addition to Alkenes: Overview
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl bromides.
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.


