Suzuki-Miyaura Cross-Coupling of Aryl Chlorides in Water Using Ligandless Palladium on Activated Carbon

Abstract

Aqueous reaction conditions that activate various aryl chlorides in Suzuki-Miyaura cross-coupling have been developed. These environment friendly conditions utilize ligandless Pd/C (Pd concentrations 0.2-2 mol%) that allow easy separation of the catalyst at the end of the reaction.

Key words: aryl chlorides - water - palladium - cross-coupling - ­biaryls

References

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Representative Procedure.
A pressure tube was charged with Pd/C (0.2 mol%; commercially available E105CA/W 5% Pd, product of Degussa AG, or self-prepared [14] ), TBAB (2 mmol), NaOH (10 mmol), phenylboronic acid (4.4 mmol) and 4-chloro-acetophenone (4 mmol). Then, H₂O (6 mL) was added and the flask was sealed with a Teflon screw cap and stirred at 100 °C for 2 h. After cooling to r.t., CH₂Cl₂ (15 mL) was added and the reaction was filtered through a plug of celite to remove the catalyst. The filter was flushed with CH₂Cl₂ (2 × 15 mL) and the combined organic phase was dried (MgSO₄), evaporated on Celite and purified by flash chromatography to yield 1-biphenyl-4-yl-ethanone (entry 2a, 776 mg, ca. 99%).