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Synlett 2005(15): 2309-2312  
DOI: 10.1055/s-2005-872661
LETTER
© Georg Thieme Verlag Stuttgart · New York

Room-Temperature Palladium-Catalyzed and Copper(I)-Mediated Coupling Reactions of Acid Chlorides with Boronic Acids under Neutral Conditions

Yasushi Nishihara*, Yoshiaki Inoue, Mamoru Fujisawa, Kentaro Takagi
Department of Chemistry, Faculty of Science, Okayama University, 3-1-1 Tsushimanaka, Okayama 700-8530, Japan
Fax: +81(86)2517855; e-Mail: ynishiha@cc.okayama-u.ac.jp;
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Publication History

Received 24 June 2005
Publication Date:
08 August 2005 (online)

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Abstract

The palladium-catalyzed cross-coupling reactions of acid chlorides with arylboronic acids in the presence of copper(I) thiophene-2-carboxylate (CuTC) as an activator under strictly non-basic and mild reaction conditions afford the unsymmetrical ­ketones in moderate to excellent yields. A wide range of substrates bearing an electron-donating or an electron-withdrawing substi­tuent on the aromatic ring is compatible.

Key words

palladium - cross-coupling reaction - boronic acid - ­copper - ketones

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Typical Procedure for the Cross-Coupling Reactions of Acid Chlorides 1 with Boronic Acids 2.
To phenylboronic acid (1a, 244 mg, 2 mmol), CuTC (191 mg, 1 mmol), Pd(dba)2 (29 mg, 0.05 mmol), and PPh3 (26.2 mg, 0.1 mmol), were added dry Et2O (30 mL) and benzoyl chloride (2a, 116 µL, 1 mmol) at r.t. The reddish brown suspension was stirred for 1 h at r.t. and monitored by GC and TLC. After completion of the reaction, the reaction mixture was passed briefly through a Celite pad. Further, the pad was washed with Et2O (2 × 10 mL). The combined organics were concentrated with a rotary evaporator to give a viscous oil or solid. The residue was purified by flash column chromatography on silica gel (hexane-EtOAc = 9:1, R f = 0.47), compound 3a (142 mg, 0.78 mmol, 78%) was obtained as a white solid. 1H NMR (300 MHz, CDCl3): δ = 7.46-7.51 (m, 4 H), 7.56-7.62 (m, 2 H), 7.79-7.83 (m, 4 H). 13C{1H} NMR (75 MHz, CDCl3): δ = 128.1, 129.9, 132.3, 137.4, 196.5.