两者同时挫败了易斯对/三 (pentafluorophenyl) 酸催化二氧化碳的脱氧化化
Andreas Berkefeld1, Warren E Piers, Masood Parvez
1Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4.
Journal of the American Chemical Society
|August 5, 2010
概括
一个丧的易斯对系统有效地通过强大的双联催化过程将二氧化碳 (CO2) 转化为甲 (CH4). 这种方法利用水化来减少二氧化碳的去氧化,为碳利用提供了一条新的途径.
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.
- 二氧化碳利用利用情况
背景情况:
- 挫败的易斯对 (FLP) 是由于硬质阻碍而保持反应的易斯酸和.
- FLPs可以激活像CO2这样的小分子,但高效的催化降解途径仍在开发中.
研究的目的:
- 通过使用丧的易斯对系统,研究二氧化碳 (CO2) 到甲 (CH4) 的脱氧降解.
- 阐明催化机制,并确定二氧化碳减排过程中的关键中间体.
主要方法:
- 使用一个丧的易斯对系统,其中包括2,2,6,6-四甲 (TMP) 和三 (pentafluorophenyl) [B(C6F5) 3].
- 采用三甲基 (Et3SiH) 作为减少剂和源.
- 使用光谱方法对反应中间体进行了表征,并分析了最终产品.
主要成果:
- 该FLP系统激活了CO2,形成了一个酸碳酸盐-TMPH离子对.
- 建立了一个双联催化循环,涉及连续的水化步骤.
- 该系统成功地将二氧化碳减少为甲 (CH4),并将 (Et3Si) 2O作为副产品,证明了活的催化系统.
结论:
- 丧的易斯对系统提供了一种强大而有效的方法,用于去氧化降低CO2到CH4.
- 鉴定到的双重催化途径突出了开发用于二氧化碳转换的新催化系统的潜力.
- 这项研究通过提供一种新的合成途径,为碳捕获和利用领域做出了贡献.
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.
02:44Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with 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...
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01:16[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.