TAILIEUCHUNG - Suzuki reactions of aryl halides with phenylboronic acid using imidazolium-based ionic liquid as a green solvent under microwave irradiation
Using the ionic liquid as the reaction solvent in conjunction with microwave irradiation, the reaction rate was dramatically enhanced, with 99% conversion being achieved within 2 minutes, while less than 5% conversion was observed after 8 hours for the reaction under conventional heating condition. Furthermore, the ionic liquid could be reused without significant degradation in activity. | Journal of Chemistry, Vol. 47 (5), P. 596 - 602, 2009 SUZUKI REACTIONS OF ARYL HALIDES WITH PHENYLBORONIC ACID USING IMIDAZOLIUM-BASED IONIC LIQUID AS A GREEN SOLVENT UNDER MICROWAVE IRRADIATION Received 26 December 2008 PHAN THANH SON NAM, TRUONG VU THANH, NGUYEN THI DUY HIEN, VO THI NGUYET Ho Chi Minh City University of Technology abstract An easily accessible ionic liquid, 1-hexyl-3-methylimidazolium bromide, was synthesized from n-hexyl bromide and N-methylimidazole under microwave irradiation condition, and characterized by 1H and 13C NMR, and MS. The ionic liquid was demonstrated to be an efficient and recyclable solvent for the Suzuki cross-coupling reaction between several aryl halides and phenylboronic acid under microwave irradiation to form biphenyls as the principal products. The most commonly used base in several Suzuki reactions, Na2CO3, was found to be significantly less effective than triethylamine for the reaction carried out in the ionic liquid. Using the ionic liquid as the reaction solvent in conjunction with microwave irradiation, the reaction rate was dramatically enhanced, with 99% conversion being achieved within 2 minutes, while less than 5% conversion was observed after 8 hours for the reaction under conventional heating condition. Furthermore, the ionic liquid could be reused without significant degradation in activity. I - INTRODUCTION Palladium-catalyzed Suzuki cross-coupling reactions have gained popularity in organic synthetic chemistry, as they have exhibited practical applications in the production of pharmaceuticals, herbicides, as well as engineering materials such as conducting polymers and liquid crystals [1 - 3]. Room temperature ionic liquids have been increasingly employed as green solvents since they are easy to recycle they possess a remarkably high thermal stability and show no effective vapour pressure, thus providing a way of avoiding the generation of contaminated waste and its subsequent treatment [4-6]. During the .
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