JoVE - Journal of Visualized Experiments
JoVE Visualize
Contact Us
这页已由机器翻译。其他页面可能仍然显示为英文。 View in English

通过催化非对称基化N-基α,β-不和乳酸的C19-Oxo Eburnane类化合物的分离选择合成

  • 0Department of Chemistry , Stanford University , Stanford , California 94305-5080 , United States.
Journal of the American Chemical Society +

|

2019年三月9日

在PubMed上查看摘要

概括

此摘要是机器生成的。

相关概念视频

Alkylation of β-Ketoester Enolates: Acetoacetic Ester Synthesis 01:07

4.6K

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...

Alkylation of β-Diester Enolates: Malonic Ester Synthesis 01:14

4.2K

Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.

The reaction proceeds via abstraction of the acidic α hydrogen from a ꞵ-diester to produce a doubly stabilized enolate ion. The nucleophilic enolate attacks the alkyl halide in an SN2 manner to form an alkylated malonic ester intermediate with a new C–C bond. Further treating the intermediate with aqueous acid or base results in the hydrolysis of the...

α-Alkylation of Ketones via Enolate Ions 01:10

3.8K

Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by resonance, and its hybrid structure exhibits negative charges on the carbonyl oxygen and the α carbon. This ambident nucleophile can attack an electrophile via two possible sites: the carbonyl oxygen, known as O-attack, or the α carbon, known as C-attack. The nucleophilic attack via the carbanionic site is preferred. This is due to the...

Factors Affecting α-Alkylation of Ketones: Choice of Base 01:10

3.6K

α-Alkylation of ketones is achieved in the presence of alkyl halides and a base. The reaction proceeds via the formation of an enolate ion followed by nucleophilic substitution. The choice of base employed is essential as it is the key factor in determining the reaction outcome.
The reaction involving bases like EtO− whose conjugate acid EtOH (pKa = 15.9) is stronger than the ketone (pKa = 19.2) results in an equilibrium mixture with higher ketone concentration. As a consequence,...

Conjugate Addition to α,β-Unsaturated Carbonyl Compounds 01:09

5.5K

α,β-Unsaturated carbonyl compounds are molecules bearing a carbonyl and alkene functionality in conjugation with each other. The conjugation in the molecule leads to three resonance structures. The hybrid form exhibits two probable electrophilic sites: the carbonyl carbon and the β carbon.

A simple nucleophilic attack at the carbonyl center results in an alkoxy intermediate, which gives the direct or 1,2-addition product upon further protonation.

When the nucleophile attacks the β carbon,...

Alkyl Halides 02:45

19.8K

Structural Properties
Alkyl halides are halogen-substituted alkanes wherein one or more hydrogen atoms of an alkane is replaced by a halogen atom such as fluorine, chlorine, bromine, or iodine. The carbon atom in an alkyl halide is bonded to the halogen atom, which is sp3-hybridized and exhibits a tetrahedral shape.
Unlike alkyl halides, compounds in which a halogen atom is bonded to an sp2 -hybridized carbon atom of a carbon-carbon double bond (C=C) are called vinyl halides. Whereas aryl...