Related Experiment Video
Updated: Sep 12, 2025
08:12
A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
10.1K
A Potassium Base-Promoted Intramolecular Enolate-Olefin Metathesis
Kazuma Sugimoto1, Takaaki Nagao1, Kazuma Kurokawa1
1Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto, 606-8501, Japan.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|August 6, 2025
Summary
This study introduces a new transition-metal-free method for creating hydroxy-substituted polycyclic aromatic hydrocarbons (PAHs). The novel approach utilizes base-promoted intramolecular enolate-olefin-metathesis chemistry for efficient synthesis.
Area of Science:
- Organic Chemistry
- Synthetic Chemistry
- Materials Science
Background:
- Polycyclic aromatic hydrocarbons (PAHs) possess unique electronic and optical properties.
- Existing synthetic methods often rely on transition metals, posing environmental and cost concerns.
Purpose of the Study:
- To develop a novel, transition-metal-free synthetic route for hydroxy-substituted PAHs.
- To explore the utility of base-promoted intramolecular enolate-olefin-metathesis chemistry in PAH synthesis.
Main Methods:
- Utilized 2-acyl-2'-alkenylbiaryl substrates.
- Employed base-promoted intramolecular enolate-olefin-metathesis.
- Incorporated [2+2]/retro-[2+2] cycloaddition sequences.
- Performed Density Functional Theory (DFT) calculations to elucidate reaction mechanisms.
Main Results:
- Successfully synthesized functionalized PAH derivatives, including enantiomerically enriched [7]helicenes.
- Demonstrated the conversion of various biaryl substrates, including heteroatom-containing compounds.
- Achieved the synthesis of π-extended arenols.
- DFT calculations indicated a stepwise process involving ionic and radical intermediates.
Conclusions:
- The developed method provides a sustainable and efficient alternative to transition-metal-catalyzed processes for PAH synthesis.
- The methodology is versatile, applicable to a range of biaryl substrates.
- Offers a new pathway for accessing complex PAH structures and functionalized arenols.
Related Concept Videos
01:10α-Alkylation of Ketones via Enolate Ions
3.3K
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...
3.3K
00:51Base-Promoted α-Halogenation of Aldehydes and Ketones
3.7K
α-Halogenation of aldehydes and ketones is a reaction involving the substitution of α hydrogens with halogens in the presence of a base. The reaction begins with the abstraction of α hydrogen by the base to produce a nucleophilic enolate ion. This intermediate undergoes a subsequent nucleophilic substitution with the halogen to produce a monohalogenated carbonyl compound. If the starting substrate has more than one α hydrogen, it is difficult to stop the reaction...
3.7K
01:23Reactivity of Enolate Ions
2.7K
Enolate ions are formed by the acid–base reaction of a carbonyl compound with a base. This leads to deprotonation of the α hydrogen atom, leading to a resonance-stabilized enolate ion where one of the contributing structures is an oxyanion, which imparts additional stability. Therefore, the proton on the α carbon is more acidic in nature than that of other sp3-hybridized C–H bonds but less acidic than those in O–H bonds where the negative charge in the conjugate...
2.7K
01:13Olefin Metathesis Polymerization: Overview
2.2K
Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists...
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists...
2.2K
01:33Regioselective Formation of Enolates
2.8K
As depicted in the figure below, the unsymmetrical ketones can form two possible enolates: less substituted or more substituted enolates. Usually, the thermodynamic enolates are formed from the more substituted α-carbon atom, while the kinetic enolates are formed faster by deprotonation from the less substituted position. The thermodynamic enolates have lower energy, so they are more stable. But the energy required to form kinetic enolates is less.
2.8K
01:10Factors Affecting α-Alkylation of Ketones: Choice of Base
3.3K
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,...
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,...
3.3K