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Synlett 2008(19): 3041-3045  
DOI: 10.1055/s-0028-1087345
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Sila-Sonogashira Cross-Coupling Reactions of Activated Aryl Chlorides with Alkynylsilanes

Yasushi Nishihara*, Eiji Inoue, Yoshiaki Okada, Kentaro Takagi
Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, 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 5 July 2008
Publication Date:
12 November 2008 (online)

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Abstract

The palladium/copper-cocatalyzed sila-Sonogashira cross-coupling reactions of activated aryl chlorides with alkynyl­silanes under strictly nonbasic conditions yield the unsymmetrical diarylethynes in moderate to good yields.

Key words

palladium - copper - Sonogashira reaction - alkynyl­silane - aryl chloride - diarylethynes

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Typical Procedure for the Sila-Sonogashira Cross-Coupling Reactions of Aryl Chlorides 2 with Alkynylsilanes 1
To a solution of Pd(OAc)2 (45 mg, 0.2 mmol, 10 mol%) and (-)-DIOP (100 mg, 0.2 mmol, 10 mol%) in dry DMF (8 mL) were added 1-(4-methoxypheny)-2-trimethylsilylethyne (1b, 519 µL, 2.4 mmol), 4-cyanophenyl chloride (2b, 275 mg, 2 mmol), and CuCl (20 mg, 0.2 mmol, 10 mol%) at r.t. The dark red suspension was heated for 12 h at 120 ˚C and monitored by GC and TLC. After completion of the reaction, the reaction mixture was quenched with 1 M HCl and extracted with Et2O (3 × 20 mL). The combined organics were washed with brine and dried over anhydrous MgSO4. Filtration and concentration with a rotary evaporator gave a viscous oil. The residue was purified by flash column chromatography on SiO2 (hexane-Et2O, 8:2, R f  = 0.39), 3h (331 mg, 1.42 mmol, 71%) was obtained as a white solid. ¹H NMR (300 MHz, CDCl3): δ = 3.84 (s, 3 H), 6.89-6.92 (m,
2 H), 7.47-7.50 (m, 2 H), 7.56-7.64 (m, 4 H).