作为终端基因的马尔科夫尼科夫选择性分子间化催化剂的有机复合物:作用范围和机制
Charles J Weiss1, Tobin J Marks
1Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
Journal of the American Chemical Society
|July 13, 2010
概括
有机 ((IV) 催化剂有效地调解基因与醇的分子间水解,实现高马尔科夫尼科夫的选择性和产量. 激素通路被抑制,动力学研究显示,基因插入Zr-SR键是限制速度的步骤.
科学领域:
- 有机金属化学 有机金属化学
- 催化剂是一种催化剂.
- 有机合成 有机合成
背景情况:
- 酸盐的化是合成有机硫化合物的关键反应.
- 开发高效和有选择性的催化系统用于水电化仍然是一个活跃的研究领域.
研究的目的:
- 报告终端基因的高效和选择性的有机基介导的分子间水合.
- 通过使用各种有机前催化剂,研究反应机制,选择性和范围.
主要方法:
- 使用了CGCZrMe2 ,Cp*ZrBn3 ,Cp*ZrCl2 ,NMe2 ,Cp*Zr2 ,ZrMe2和ZrNMe2 的催化剂,用于化.
- 进行了动力学研究,标记和激活参数测量.
- 研究了激素抑制剂的作用,并分析了反应中间体.
主要成果:
- 获得高马尔科夫尼科夫的选择性 (高达99%) 和收益率 (>90%) 用各种类硫醇对终端基因进行化.
- 证明了准备性规模合成,具有72%的孤立产量和99%的马尔科夫尼科夫选择性.
- 确定了基因插入Zr-SR键,其次是醇诱导的Zr-C质解,作为限制周转的步骤.
结论:
- 有机 ((IV) 预催化剂在选择性分子间化中非常有效.
- 反应通过一种涉及基内插入和质溶解的机制进行,具有二维催化剂静止状态的潜力.
- 可以抑制激进路径,确保高马尔科夫尼科夫的选择性.
相关概念视频
02:47Alkynes 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.
02:35Electrophilic 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.
02:40Alkynes 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.
02:24Reduction 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.
01:25Radical 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.
02:36Regioselectivity 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.