削弱C-O键:Ti(III),是一种新的试剂,用于酒精脱氧和碳结合的olefination
Horacio R Diéguez1, Armando López, Victoriano Domingo
1Department of Organic Chemistry, Institute of Biotechnology, University of Granada, Avda. Fuentenueva, 18071 Granada, Spain.
Journal of the American Chemical Society
|December 17, 2009
概括
纽根特的试剂含有 (III) 复合物,可显著降低C-O键裂解的激活能量. 这使得酒精的新型去氧化降解成为可能,并揭示了 (III) 在麦克默里油性化中的参与.
科学领域:
- 有机化学 有机化学
- 有机金属化学 有机金属化学
- 计算化学计算化学
背景情况:
- 麦克默里反应通常涉及Ti(II) 或Ti(0) 物种.
- 纽根特的试剂是低价值的来源.
- 以为媒介的降解机制是复杂的.
研究的目的:
- 研究在C-O键同解中的作用.
- 为了探索纽根特试剂的新合成应用.
- 为了阐明以为媒介的麦克默里油精加工的机制.
主要方法:
- 密度函数理论 (DFT) 的计算.
- 使用Nugent的试剂进行实验性有机合成.
- 对介导反应的机制研究.
主要成果:
- 氧-或氧-Ti (III) 复合物降低了C-O键同解的激活能量.
- 开发了一种单步脱氧降低酒精的方法.
- Ti(III) 皮纳科拉特被确定为纽根特的试剂介导麦克默里烯酸精细化中的关键中间体,挑战了以前的假设.
- 使用Cp(2) TiCl(2) 和TMSCl实现了这些反应的催化版本.
结论:
- (III) 在C-O键激活和还原过程中起着至关重要的作用.
- 努根特的试剂在有机合成中提供了多样化的应用,包括酒精脱氧和新的麦克默里炼途径.
- 对介导反应的机理学理解,特别是麦克默里油性化反应,已经得到了显著的进展.
相关概念视频
02:37Oxidation of Alcohols
In this lesson, the oxidation of alcohols is discussed in depth. The various reagents used for oxidation of primary and secondary alcohols are detailed, and their mechanism of action is provided.
The process of oxidation in a chemical reaction is observed in any of the three forms:
The process of oxidation in a chemical reaction is observed in any of the three forms:
01:27Vicinal Diols via Reductive Coupling of Aldehydes or Ketones: Pinacol Coupling Overview
Wilhelm Rudolph Fittig discovered the pinacol coupling reaction in 1859. It is a radical dimerization reaction and involves the reductive coupling of aldehydes or ketones in the presence of hydrocarbon solvent to yield vicinal diols.
02:35Acid-Catalyzed Dehydration of Alcohols to Alkenes
In a dehydration reaction, a hydroxyl group in an alcohol is eliminated along with the hydrogen from an adjacent carbon. Here, the products are an alkene and a molecule of water. Dehydration of alcohols is generally achieved by heating in the presence of an acid catalyst. While the dehydration of primary alcohols requires high temperatures and acid concentrations, secondary and tertiary alcohols can lose a water molecule under relatively mild conditions.
01:27Aldol Condensation with β-Diesters: Knoevenagel Condensation
The Knoevenagel condensation is an aldol-type reaction involving the condensation of aldehydes or ketones with active methylene compounds such as β-diesters to produce substituted olefins.
01:19Aldehydes and Ketones with Alcohols: Hemiacetal Formation
Similar to water, alcohols can add to the carbonyl carbon of the aldehydes and ketones. The addition of one molecule of alcohol to the carbonyl compound forms the hemiacetal or half acetal. As depicted below, in a hemiacetal, the carbon is directly linked to an OH and OR group.
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.