Azulene Functionalization by Iron-Mediated Addition to a Cyclohexadiene Scaffold
Petter Dunås1, Lloyd C Murfin2, Oscar J Nilsson1
1Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-41296 Gothenburg, Sweden.
The Journal of Organic Chemistry
|October 21, 2020
Summary
This study demonstrates the functionalization of azulenes using iron carbonyl complexes, yielding valuable substituted azulene products with unique halochromic properties. These methods open pathways to novel conjugated ketones and fused tetracycles.
Area of Science:
- Organic Chemistry
- Organometallic Chemistry
Background:
- Azulenes are non-benzenoid aromatic compounds with unique electronic properties.
- Functionalization of azulenes is crucial for developing new materials and pharmaceuticals.
Purpose of the Study:
- To develop a novel method for azulene functionalization using cationic iron carbonyl diene complexes.
- To explore the synthesis of diverse 1-substituted azulenes.
Main Methods:
- Reaction of various azulenes with electrophilic η5-iron carbonyl diene complexes.
- Characterization of products using UV-vis/fluorescence spectroscopy.
- Decomplexation and derivatization of iron-azulene adducts.
Main Results:
- Successful functionalization of azulenes under mild conditions.
- Coupling products obtained in yields ranging from 43-98%.
- Observed interesting halochromic properties in the synthesized products.
Conclusions:
- The developed method provides efficient access to diverse 1-substituted azulenes.
- The synthesized compounds exhibit tunable electronic and optical properties.
- This work expands the synthetic utility of azulenes in organic synthesis.
Related Concept Videos
01:27Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
2.6K
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, β-ketoesters, or β-diketones) and α,β-unsaturated carbonyl acceptors. Named after Sir Robert Robinson, who discovered it, this reaction yields a six-membered ring with three new C–C bonds (two σ bonds and one π bond).
2.6K
![[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12417.jpg&w=3840&q=75)
01:16[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
11.7K
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.
11.7K
01:16Cycloaddition Reactions: Overview
3.2K
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
3.2K
01:18Benzene to 1,4-Cyclohexadiene: Birch Reduction Mechanism
2.5K
Birch reduction uses solvated electrons as reducing agents. The reaction converts benzene to 1,4-cyclohexadiene. The reaction proceeds by the transfer of a single electron to the ring to form a benzene radical anion. This anion is highly basic—it abstracts a proton from the alcohol to form a cyclohexadienyl radical. Another single electron transfer gives the cyclohexadienyl anion. A proton transfer from the alcohol forms 1,4-cyclohexadiene. Since this reduction occurs via radical anion...
2.5K
01:28Reduction of Benzene to Cyclohexane: Catalytic Hydrogenation
5.4K
Unlike the easy catalytic hydrogenation of an alkene double bond, hydrogenation of a benzene double bond under similar reaction conditions does not take place easily. For example, in the reduction of stilbene, the benzene ring remains unaffected while the alkene bond gets reduced. Hydrogenation of an alkene double bond is exothermic and a favorable process. In contrast, to hydrogenate the first unsaturated bond of benzene, an energy input is needed; that is, the process is endothermic. This is...
5.4K
01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
2.4K
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
2.4K