Synlett 2005(1): 176-178  
DOI: 10.1055/s-2004-836033
LETTER
© Georg Thieme Verlag Stuttgart · New York

Intramolecularly Activated Vinylsilanes: Fluoride-Free Cross-Coupling of (Z)-β-(Trialkylsilyl)acrylic Acids

Mitsuru Shindo*, Kenji Matsumoto, Kozo Shishido
Institute of Health Biosciences, The University of Tokushima Graduate School, Sho-machi 1, Tokushima 770-8505, Japan
Fax: +81(88)6337294; e-Mail: shindo@ph.tokushima-u.ac.jp.;
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Publikationsverlauf

Received 13 October 2004
Publikationsdatum:
29. November 2004 (online)

Abstract

The fluoride-free palladium-catalyzed cross-coupling reaction of trialkyl(vinyl)silanes activated by the intramolecular pentacoordination of carboxylic acid at the Z-β-position is described.

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General Procedure for the Cross-Coupling Reaction of a ( Z )-β-(Trimethylsilyl)acrylic Acid 1a with Iodobenzene. To a solution of 1a (35 mg, 0.141 mmol) and Cs2CO3 (230 mg, 0.705 mmol) in DME (10 mL) were added sequentially iodobenzene (43 mg, 0.211 mmol) and Pd2 (dba)3·CHCl3 (7 mg, 0.00705 mmol) at room temperature. After the mixture was stirred at 60 °C for 22 h, the solvents were evaporated to give a residue, which was diluted with CH2Cl2 and acidified with 6 M HCl (aq). The mixture was extracted with CH2Cl2, and the combined organic layer was washed with H2O and brine, and dried over MgSO4. The organic phase was concentrated in vacuo to give a crude product, which was purified by silica gel column chromatography (hexane-EtOAc, 10-25%) to afford 27 mg of a mixture of 2a (72%) and 3a (6%). After recrystallization from CCl4-hexane, compound 2a was isolated as colorless needles. (Z)-2-Methyl-3,4-diphenyl-2-butenoic acid (2a): [6] mp 107.6-108.0 °C. 1H NMR (400 MHz, CDCl3): δ = 2.14 (s, 3 H), 3.83 (s, 2 H), 7.01-7.08 (m, 4 H), 7.13-7.24 (m, 6 H). IR (CHCl3): 3062, 1691 cm-1.