Carbon–Heteroatom Bond Formation via Coupling Reactions Performed on a Magnetic Nanoparticle Bed

Mahmood Tajbakhsh,Ali Ramezani,Carlos J Durán-Valle,Ignacio M López-Coca,Mohammad Qandalee,Mobina Falahati,Silvia Izquierdo

doi:10.3390/appliedchem1020007

Abstract

Cross-coupling reactions leading to carbon–heteroatom bonds yield compounds that attract substantial interest due to their role as structural units in many synthetic protocols for bioactive and natural products. Therefore, many research works aim at the improvement of heterogeneous catalytic protocols. We have studied the use of magnetite nanoparticles and solid base compounds in organic synthetic reactions in carbon–heteroatom bond formation because they can be flocculated and dispersed, and reversibly controlled by applying a magnetic field. In this work, we have developed an efficient and simple synthetic approach for the C–O/C–N cross-coupling reaction under ligand-free conditions by using CuI as a catalyst and KF/Fe3O4 as a base. We performed the nucleophilic aromatic substitution of electron-deficient aryl halides and phenols. It was found that both the solvent nature and the base have a profound influence on the reaction process. This approach affords good to excellent yields of arylated products. KF/Fe3O4 displayed convenient magnetic properties and could be easily separated from the reaction using a magnet and recycled several times without significant loss of catalytic activity. This method has been successfully investigated for the Ullmann coupling reaction.

Highlights

Copper chemistry is extremely important because it can form Cu0, CuI, CuII, and CuIII oxidation states allowing one-electron or two-electron exchange
Nucleophilic aromatic substitution (SNAr) reaction is an important methodology for the preparation of diaryl ethers from activated aryl halides or phenols [6,7]; for example, the coupling of activated aryl halides with different phenolic substrates in the presence of potassium fluoride/Clinoptilolite (KF/CP) was studied by Hosseini et al [8]
Our interest in organic synthetic reactions developed by magnetite nanoparticle conditions prompted us to study the application of solid base compounds in carbon–heteroatom bond formation because they can be flocculated and dispersed and reversibly controlled by applying a magnetic field

Summary

Introduction

Copper chemistry is extremely important because it can form Cu0, CuI, CuII, and CuIII oxidation states allowing one-electron or two-electron exchange. The different oxidation states can make useful interactions with different functional groups as Lewis acid or π-coordination These features show remarkable activities allowing copper to catalyze different reactions [1]. Zhang and co-workers used nanoparticle Fe3O4-encapsulated CuO as a heterogeneous catalyst in the synthesis of diaryl ethers by the cross-coupling reaction; they found that Fe3O4 alone did not show any catalytic effect [28]. The base catalyst KF/CaO–Fe3O4 was used to catalyze the transesterification of Stillingia oil and methanol for biodiesel production [29] Using this method, we tried to prepare a nanomagnetic solid base catalyst KF/Fe3O4 that has an average particle diameter of ca. To the best of our knowledge, this is the first report on the use of KF/Fe3O4 in the C–N bond formation in the arylation of amides, carbazoles, and indoles and the synthesis of diaryl ethers

Methods

Results

Conclusion