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Synlett 2005(20): 3083-3086  
DOI: 10.1055/s-2005-922756
LETTER
© Georg Thieme Verlag Stuttgart · New York

Water-Promoted Suzuki Reaction in Room Temperature Ionic Liquids

Bingwei Xina,b, Yuhong Zhang*a, Leifang Liua, Yanguang Wanga
a Department of Chemistry, Zhejiang University, Hangzhou 310027, P. R. of China
Fax: +86(571)87951512; e-Mail: yhzhang@zjuem.zju.edu.cn;
b Department of Chemistry, Dezhou University, Dezhou 253023, P. R. of China
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Publication History

Received 22 August 2005
Publication Date:
28 November 2005 (online)

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Abstract

The Suzuki reaction was successfully performed by using Pd(OAc)2 as the catalyst in a mixture of water and ionic liquids in a short reaction time in air. Water was found to have a remarkable rate accelerating effect on the Suzuki reaction in ionic liquids. The Pd(OAc)2-[bmim][PF6] can be reused seven times only with a small deactivation of reactivity.

Key words

Suzuki reaction - ionic liquid - palladium acetate

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General Procedure for Suzuki Reaction. To a mixture of [bmim][PF6] and H2O (3:1 g) {or [bmim][BF4]-H2O = 3:3 g} was added Na2CO3 (0.212 g,
2 mmol) and Pd (OAc)2 (4 mg, 1.8 mol%).Then, the mixture was heated to 100 °C under stirring. Afterward, aryl halides (1 mmol) and arylboronic acid (1.5 mmol) was added in the solution and the reaction carried out at 100 °C for the indicated time. After the reaction, the reaction solution was cooled to r.t. and the resulting suspension was extracted with Et2O (4 × 5 mL). In the recycle experiment, the residue after the extraction was washed with H2O (3 × 6 mL) and then was subjected to a second run of the Suzuki reaction by charging with the same substrates (bromotoluene, phenylboronic acid, H2O and Na2CO3) without further addition of Pd(OAc)2 or ILs. The combined diethyl ether phase was analyzed by GC/MS and then concentrated. The further purification of the product was achieved by flash chromatography on a silica gel column. In the recycle experiments, the amount of the [bmim][PF6]-H2O was doubled.