Related Experiment Video
Updated: Feb 10, 2026
05:07
Microwave-Assisted Preparation of 1-Aryl-1H-pyrazole-5-amines
Published on: June 23, 2019
7.1K
The first samarium(II)-mediated aryl radical cyclisation onto an aromatic ring
Hiroaki Ohno1, Hiroki Iwasaki, Toru Eguchi
1Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan.
Chemical Communications (Cambridge, England)
|October 7, 2004
Summary
Samarium(II) iodide mediated intramolecular arylation of aryl radicals offers a novel route to spirocycles and fused rings. Reaction conditions dictate product formation, yielding either reduced cine-cyclised products or rearomatised fused systems.
Area of Science:
- Organic Chemistry
- Radical Reactions
- Synthetic Methodology
Background:
- Intramolecular arylation is a key transformation in organic synthesis.
- Aryl radical cyclizations provide access to complex molecular architectures.
- Controlling the outcome of radical reactions remains a significant challenge.
Purpose of the Study:
- To investigate the use of samarium(II) iodide (SmI2) and hexamethylphosphoramide (HMPA) for intramolecular arylation of aryl radicals.
- To explore the influence of reaction conditions, specifically the presence or absence of isopropanol (i-PrOH), on the cyclization pathway and product formation.
- To develop a novel synthetic route to spirocycles and fused ring systems.
Main Methods:
- Generation of aryl radicals using SmI2/HMPA.
- Intramolecular cyclization reactions in the presence and absence of i-PrOH.
- Analysis of reaction products using spectroscopic techniques.
Main Results:
- SmI2/HMPA mediated intramolecular arylation of aryl radicals.
- In the presence of i-PrOH, spirocycles and/or reduced cine-cyclised products were obtained.
- In the absence of i-PrOH, rearomatised fused rings were exclusively formed.
Conclusions:
- The SmI2/HMPA system effectively mediates intramolecular arylation of aryl radicals.
- Reaction conditions, particularly the presence of a proton source like i-PrOH, are crucial for controlling the cyclization pathway and product selectivity.
- This study presents a versatile method for synthesizing diverse spirocyclic and fused aromatic compounds.
More Related Videos
14:22Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
Published on: April 15, 2013
20.8K
12:22Preparation and Use of Samarium Diiodide SmI2 in Organic Synthesis: The Mechanistic Role of HMPA and NiII Salts in the Samarium Barbier Reaction
Published on: February 4, 2013
34.2K
Related Concept Videos
01:27Radicals
747
Roots, often written as radicals, identify the quantity that must be raised to a specific exponent to produce a given value. A radical expression consists of two main components: the radicand, which is the value placed inside the root symbol, and the index, which indicates the degree of the root being taken. The notation n√a indicates the principal nth root of a. If n equals 2, the operation is the square root, while n = 3 defines the cube root. When n is even, a negative radicand does...
747
01:10Nomenclature of Aryl and Heterocyclic Amines
3.2K
The simplest aromatic amine is phenylamine, which contains an –NH2 functionality directly attached to an aromatic ring. The name aniline is designated for this skeleton. As shown in Figure 1, the common names of the functionalized anilines involve prefixes ortho-, meta-, and para- to indicate the substitution position. Different functionalized aniline derivatives also have notable trivial names.
3.2K
01:14Nucleophilic Aromatic Substitution of Aryldiazonium Salts: Aromatic SN1
2.8K
Treating arylamines with nitrous acid gives aryldiazonium salts that are effective substrates in nucleophilic aromatic substitution reactions. The diazonio group in these salts can be easily displaced by different nucleophiles, yielding a wide variety of substituted benzenes. The leaving group departs as nitrogen gas, and this easy elimination is the driving force for the substitution reaction.
In the Sandmeyer reaction, for example, the diazonio group is replaced by a chloro, bromo,...
In the Sandmeyer reaction, for example, the diazonio group is replaced by a chloro, bromo,...
2.8K
01:16Radical Reactivity: Nucleophilic Radicals
2.7K
Radicals adjacent to electron-donating groups are called nucleophilic radicals. These radicals readily react with electrophilic alkenes. The SOMO–LUMO interactions are the driving force for the reaction, where the high-energy SOMO of the electron-rich, nucleophilic radicals interacts with the low-energy LUMO of the electron-deficient, electrophilic alkenes. Such SOMO–LUMO interactions are the basis of reactive radical traps, affecting the selectivity in radical reactions. For...
2.7K
01:02Radical Reactivity: Electrophilic Radicals
2.5K
Radicals adjacent to electron‐withdrawing groups are called electrophilic radicals. These radicals readily react with nucleophilic alkenes. For example, the malonate radical, in which the radical center is flanked by two electron‐withdrawing groups, reacts readily with butyl vinyl ether, which consists of an electron‐donating oxygen substituent. The reaction between electrophilic malonate radical and nucleophilic vinyl ether is favored because the radical has a...
2.5K
01:20Radical Autoxidation
3.2K
The oxidation of an organic compound in the presence of air or oxygen is called autoxidation. For example, cumene reacts with oxygen to form hydroperoxide. Autoxidation involves initiation, propagation, and termination steps. Many organic compounds are susceptible to autoxidation—especially ethers in the presence of oxygen, which form hydroperoxides. Even though this reaction is slow, old ether bottles contain small amounts of peroxide, which leads to laboratory explosions during ether...
3.2K