Synthesis of Xylyl-Linked Bis-Benzimidazolium Salts and Their Application in the Palladium-Catalyzed Suzuki–Miyaura Cross-Coupling Reaction of Aryl Chlorides

Tsui Wang,Yu-Ting Lai,Shu-Jyun Huang,Ta-Jung Lu,Ting-Rong Wei,Dong-Sheng Lee

doi:10.3390/catal11070817

Tsui Wang, Yu-Ting Lai + Show 4 more

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https://doi.org/10.3390/catal11070817

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Abstract

A new series of xylyl-linked bis-benzimidazolium salts were efficiently prepared using a simple preparation method from bis-benzimidazolium precursors featuring highly tunable linkers and wingtips. A highly efficient Suzuki–Miyaura cross-coupling reaction of aryl chlorides within the range of 0.5–2.0 mol% Pd-catalyst loading was observed. Also, di-ortho-substituted biaryl synthesis was achieved.

Highlights

The palladium-catalyzed Suzuki–Miyaura cross-coupling reaction (SMC), which involves the combination of an aryl halide with an arylboronic acid in the presence of a Pd catalyst, is one of the most practical protocols by which to achieve C–C bond formation [1,2,3,4,5]
According to Scheme 1, the bis-benzimidazolium salts 3 were prepared by the combiAccording to Schemeof1,the thecorresponding bis-benzimidazolium salts 3 were prepared by the comnation of two equivalents
A series of new xylyl-linked bis-benzimidazolium salts 3a–3f were effectively synthesized via a simple synthetic route using cheap reactants

Summary

Introduction

The palladium-catalyzed Suzuki–Miyaura cross-coupling reaction (SMC), which involves the combination of an aryl halide with an arylboronic acid in the presence of a Pd catalyst, is one of the most practical protocols by which to achieve C–C bond formation [1,2,3,4,5]. Aryl chlorides, which are less expensive and more diverse than aryl bromides and iodides, are challenging compounds to use in SMC reactions due to their low C–Cl bond reactivity [6]. Numerous successful examples using a combination of phosphine ligands with Pd have been reported, the disadvantages of using such ligands are their difficult preparation, air-sensitivity, expense, and toxicity [7,8,9]. Compared with bulky tertiary phosphines, these new NHC ligands exhibit strong σ-donor but poor π-acceptor properties [10]

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Conclusion