“On-water” Hiyama coupling catalyzed by CNC pincer complexes of Pd(II)

Raul Sanmartin,Esther Domínguez,Maria Teresa Herrero,Blanca Inés,Isabel Moreno,María Jesús Moure,Martin A Iglesias-Arteaga

doi:10.3998/ark.5550190.0012.315

Abstract

The catalytic activity of two hydrophilic CNC-type palladium pincer complexes is evaluated in the coupling between trimethoxyphenylsilane and aryl bromides. A wide range of assays is performed for each palladium source, and alkaline aqueous conditions turn out to be the most efficient for the target Hiyama coupling, which is applied to the synthesis of several biaryls. In addition, the direct reuse of the aqueous layer containing the catalyst is also conducted with good yield.

Highlights

The palladium-catalyzed C-C bond formation between aryl, alkenyl, or alkyl halides or pseudohalides and organosilanes, first reported by Yasuo Hatanaka and Tamejiro Hiyama in 1988, is a powerful, alternative procedure to other established procedures like Suzuki or Stille couplings.[1]
The presence of fluoride ions (KF, Bu4NF, etc.) was a requirement for the transmetallation step in the initial reports, later it was discovered that sodium or potassium hydroxide could replace the later reagents/additives for this task.1b,2 several improvements to the initial conditions have been made in the last decades, and several palladium sources and ligands have been employed so far in this context.[3]
In contrast with other palladium-catalyzed cross-coupling reactions, very scarce examples of the use of pincer complexes in Hiyama couplings can be found in the literature.[4]

Summary

Introduction

The palladium-catalyzed C-C bond formation between aryl, alkenyl, or alkyl halides or pseudohalides and organosilanes, first reported by Yasuo Hatanaka and Tamejiro Hiyama in 1988, is a powerful, alternative procedure to other established procedures like Suzuki or Stille couplings.[1]. Following our research on the application of sustainable media to cross coupling reactions,[7] most of the assays based on hydroxide bases were conducted in aqueous media, and polyethylene glycol 400 (PEG 400)[8] was employed in this context.

Results

Conclusion