Suzuki-Miyaura C-C Coupling Reactions Catalyzed by Supported Pd Nanoparticles for the Preparation of Fluorinated Biphenyl Derivatives

Roghayeh Erami,Sanjiv Prashar,Diana Díaz-García,Mehdi Amirnasr,Mariano Fajardo,Antonio Rodríguez-Diéguez,Santiago Gómez-Ruiz

doi:10.3390/catal7030076

Abstract

Heterogeneous recyclable catalysts in Suzuki-Miyaura C-C coupling reactions are of great interest in green chemistry as reusable alternatives to homogeneous Pd complexes. Considering the interesting properties of fluorinated compounds for the pharmaceutical industry, as precursors of novel materials, and also as components of liquid crystalline media, this present study describes the preparation of different fluorinated biphenyl derivatives by Suzuki-Miyaura coupling reactions catalyzed by a heterogeneous system (G-COOH-Pd-10) based on Pd nanoparticles supported onto COOH-modified graphene. The catalytic activity of the hybrid material G-COOH-Pd-10 has been tested in Suzuki-Miyaura C–C coupling reactions observing excellent versatility and good conversion rates in the reactions of phenylboronic acid, 4-vinylphenylboronic acid, 4-carboxyphenylboronic acid, and 4-fluorophenylboronic acid with 1-bromo-4-fluorobenzene. In addition, the influence of the arylbromide has been studied by carrying out reactions of 4-fluorophenylboronic acid with 1-bromo-2-fluorobenzene, 1-bromo-3-fluorobenzene, 1-bromo-4-fluorobenzene, 2-bromo-5-fluorotoluene, and 2-bromo-4-fluorotoluene. Finally, catalyst recyclability tests show a good degree of reusability of the system based on G-COOH-Pd-10 as the decrease in catalytic activity after five consecutive catalytic cycles in the reaction of 1-bromo-4-fluorobenzene with 4-florophenylboronic acid at 48 hours of reaction is lower than 8% while in the case of reactions at three hours the recyclability of the systems is much lower.

Highlights

Palladium-catalyzed reactions have been one of the main methods for C-C cross-coupling processes [1]
Supported palladium nanoparticles were prepared by the reaction of commercial COOH-modified graphene (G-COOH) with different amounts of [PdCl2] in toluene for 48 hours
This synthetic method requires the reduction of the organometallic palladium complex which is achieved by toluene and the carbon atoms at the surface of the graphene which presumably act as the reducing agents

Summary

Introduction

Palladium-catalyzed reactions have been one of the main methods for C-C cross-coupling processes [1]. Suzuki-Miyaura are one of the most widely used reactions for the preparation of biphenyl derivatives [2] These reactions have been principally carried out using homogeneous catalysts based on simple or sophisticated Pd complexes [2,3,4,5]. The current needs of industry and the search for greener alternatives to these catalyst are pushing the development of new heterogeneous and recyclable systems [6]. These heterogeneous C-C coupling catalysts are based on either supported palladium complexes [7,8] or supported palladium nanoparticles [9].

Methods

Results

Conclusion