用费舍尔碳化合物复合物对乙醇进行灾难选择性循环化
José Barluenga1, Marcos G Suero, Ivan Pérez-Sanchez
1Instituto Universitario de Química Organometálica "Enrique Moles" Unidad Asociada al CSIC, Universidad de Oviedo Julián Clavería 8, 33006 Oviedo, Spain. barluenga@uniovi.es
Journal of the American Chemical Society
|February 9, 2008
概括
这项研究引入了一种使用碳复合物和乙烯酸盐合成替代环醇的新型环化方法. 该过程为创建复杂的循环有机分子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
- 有机合成 有机合成
- 碳烯化学 碳烯化学
背景情况:
- 碳化合物复合物是有机合成中的多功能试剂.
- 循环化反应对于构建应变环系统至关重要.
- 开发用于循环醇合成的二元选择性方法是一个持续的挑战.
研究的目的:
- 开发一种新型的1,2,2,3-四替代环醇的二选择合成方法.
- 为了研究碳复合物的反应机制与基乙酸盐.
- 探索这种新型循环化方法的范围和局限性.
主要方法:
- 复合物与各种替代基乙烯酸盐的复合物的阿里尔/异阿里尔 methoxycarbene的反应.
- 控制温度反应范围从-78°C到室温.
- 通过使用MeOTf或Me3SiCl. quenching来分离环醇产品和相关中间体.
主要成果:
- 成功的二聚体选择合成1,2,2,3-四替代环醇.
- 观察了一种异常,即循环赫萨烯酸乙酸盐产生了双循环的2 - - - - - - - - - - - - - - - - - 化物.
- 作为副产品的1,2-dimethoxycyclopropanes和1-methoxy-2-trimethylsilyloxycyclopropanes的分离.
- (3-oxoalkyl) 五碳基酸盐中间体的鉴定.
结论:
- 反应是通过分子内添加碳基组到稳定中间体进行的.
- 这种方法代表了一种新的循环化途径,类似于费舍尔碳复合反应.
- 这项研究扩大了碳复合物的合成实用性,用于生成复杂的循环结构.
相关概念视频
01:19Types of Enols and Enolates
Aldehydes and ketones form enols, although only about 1% of the enol is present at the equilibrium for simple monocarbonyl compounds. The enol form is undetectable for acetaldehyde, present as only 1.5 × 10−4 % of acetone, and present as only 1.2% of cyclohexanone. Two kinds of regioisomeric enols are possible for unsymmetrical ketones, and their net composition is 1% at equilibrium. This instability is due to the lower bond energy of C=C than the C=O group. The additional instability of enols...
01:10α-Alkylation of Ketones via Enolate Ions
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01:12Stereochemical Effects of Enolization
The chiral α-carbon of the carbonyl compound is the stereocenter of the molecule. As shown in the figure below, when such a carbonyl compound undergoes racemization under an acidic or basic condition, an achiral enol is formed.
01:18Reactivity of Enols
Enols are a class of compounds where a hydroxyl group is attached to a carbon–carbon double bond, which implies that it is a vinyl alcohol. A carbonyl compound with an α hydrogen undergoes keto–enol tautomerism and remains in equilibrium with its tautomer, the enol form. Usually, the keto tautomer is present in a higher concentration than the enol tautomer due to the higher bond energy of C=O compared to C=C. Moreover, the direction of the keto–enol equilibrium is governed by factors like...
01:13Intramolecular Claisen Condensation of Dicarboxylic Esters: Dieckmann Cyclization
Dieckmann cyclization is an intramolecular Claisen condensation of diesters. The reaction occurs in the presence of a base and generates a cyclic β-ketoester as the final product. Commonly, 1, 6 and 1, 7-diesters are preferred substrates for the reaction since the generated five, and six-membered cyclic β-keto esters are particularly more stable.
01:07Alkylation of β-Ketoester Enolates: Acetoacetic Ester Synthesis
Acetoacetic ester synthesis is a method to obtain ketones from alkyl halides and β-keto esters. The reaction occurs in the presence of an alkoxide base that abstracts the acidic proton of the β-keto esters. The step results in an enolate ion which is doubly stabilized. The enolate then reacts with an alkyl halide via the SN2 process to produce an alkylated ester intermediate with a new C–C bond. The hydrolysis of the intermediate, followed by acidification, results in an alkylated β-keto acid.