终端基因与B2的Pt催化对抗选择性二氧化解 (Pt-catalyzed enantioselective diboration of terminal alkenes with B2 (((pin) 2) 进行了催化
Laura T Kliman1, Scott N Mlynarski, James P Morken
1Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA.
Journal of the American Chemical Society
|August 26, 2009
概括
催化对基的酶选择性玻利化产生了性二醇. 这种高效的方法使用较低的催化剂负载,并提供多功能产品形成途径.
科学领域:
- 有机金属化学 有机金属化学
- 不对称的催化剂.
- 合成有机化学 合成有机化学
背景情况:
- 的1,2-和1,4-二醇是有机合成中有价值的构建模块.
- 为它们的不对称合成开发高效的催化方法仍然是一个关键的挑战.
- 催化为C-B键形成提供了独特的反应性.
研究的目的:
- 描述一种新的催化简单单基单替代的酶选择性玻利化.
- 在这种转换中探索易于获得的性斯酸联体的实用性.
- 为了证明从基基前体中合成的1,2-和1,4-二醇.
主要方法:
- 在催化后的终端基中加入 bis (((pinacolato) diboron 的反选择性添加.
- 为了立体化学控制,使用了一种性素酸联体.
- 使用的催化剂负载仅为1mol%的.
- 随后的氧化中介1,2-bis(甲酸) Ester 成为的1,2-diols.
- 介质的同质化/氧化,使其成为的1,4-二醇.
主要成果:
- 成功的Pt-催化对各种单替代基的反选择性玻利化.
- 在低催化剂负载 (1 mol % Pt) 时观察到高效率.
- 证明了从同一中间体中合成性1,2-二醇和性1,4-二醇的合成.
结论:
- 已经开发出一种新的,高效的Pt-催化方法,用于从烯中合成奇拉二醇的酶选择性合成.
- 该方法非常通用,可以访问1,2-和1,4-二醇结构.
- 使用低催化剂负载和易于获得的配体使这种方法对合成应用具有吸引力.
相关概念视频
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.
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
03:08Hydroboration-Oxidation of Alkenes
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
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.
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.
02:24Reduction 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.