通过容易和选择性的诱导的B-H激活,前所未有的功能化碳衍生物
Zhaojin Wang1, Hongde Ye, Yuguang Li
1State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, Jiangsu 210093, China.
Journal of the American Chemical Society
|July 10, 2013
概括
这项研究揭示了新型的17电子复合物,作为多功能中间体. 这些复合物能够通过介导的B-H激活来有效合成独特的功能化碳酸衍生物.
科学领域:
- 有机金属化学 有机金属化学
- 化学 化学 化学
- 碳化合物合成的方法
背景情况:
- 16电子复合体在有机金属合成中作为前体.
- 碳衍生物具有独特的结构和电子特性.
- 目前正在开发功能化碳酸的新型合成途径.
研究的目的:
- 为了合成和描述新型的17电子复合物.
- 为了研究这些偏磁复合物的反应性和合成效用.
- 为功能化碳衍生物开发高效的介导路径.
主要方法:
- CpCoS2C2B10H10与各种基因的反应.
- 描述17电子复合物及其衍生物.
- 密度函数理论 (DFT) 计算以阐明反应机制.
- 在不同的条件下 (空气,湿度,,AlCl3,加热) 探索反应性.
主要成果:
- 形成两种类型的17电子复合物 (2a-d和3a-d) 与norbornyl carborane部分.
- 证明C-S债券裂变导致没有的碳衍生物 (4a-d,5a-d).
- 在Co-S键中插入基因,产生乙烯硫化碳酸 (7a-d, 8a-d).
- 在特定条件下观察到的Retro-Diels-Alder产品 (9a-d) 和[1,2]-H转移产品 (10b,c).
结论:
- 17电子复合体是有价值的合成中间体.
- 以为媒介的B-H激活提供了对各种功能化碳酸的有效访问.
- 对于传统方法无法获得的碳衍生物,已经建立了新的合成途径.
相关概念视频
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.
02:36Regioselectivity 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.
02:47Alkynes 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.
02:15Preparation of Alcohols via Addition Reactions
Overview
The acid-catalyzed addition of water to the double bond of alkenes is a large-scale industrial method used to synthesize low-molecular-weight alcohols. An acidic atmosphere is required to allow the hydrogen in the water molecule to act as an electrophile and attack the double bond in an alkene. The addition of a proton to the double bond creates a carbocation intermediate. The proton preferentially bonds to the less substituted end of the double bond to create a more stable carbocation...
The acid-catalyzed addition of water to the double bond of alkenes is a large-scale industrial method used to synthesize low-molecular-weight alcohols. An acidic atmosphere is required to allow the hydrogen in the water molecule to act as an electrophile and attack the double bond in an alkene. The addition of a proton to the double bond creates a carbocation intermediate. The proton preferentially bonds to the less substituted end of the double bond to create a more stable carbocation...
01:15α-Bromination of Carboxylic Acids: Hell–Volhard–Zelinski Reaction
The method to achieve α-brominated carboxylic acids using a mixture of phosphorus tribromide and bromine is known as the Hell–Volhard–Zelinski reaction. The reaction is catalyzed by phosphorus tribromide, which can be used directly or produced in situ from red phosphorus and bromine. The mechanism comprises PBr3 catalyzed conversion of acid to acid bromide and hydrogen bromide. The acid bromide enolizes to its enol form in the presence of HBr. The nucleophilic enol attacks the bromine molecule...
02:10Carbocations
Carbocations are one of the reaction intermediates formed during several nucleophilic substitutions or elimination reactions. A carbocation is an electron-deficient species with the central carbon atom having six electrons and three bonded atoms. The central carbon in a carbocation is sp2 hybridized with trigonal planar geometry. It has an empty p orbital perpendicular to the plane of the structure that can accept electrons. Thus, carbocations act as strong electrophiles and may react with any...