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

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.

Key words

alkenes - carboxylic acids - cross-coupling - palladium - silicon

References

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9

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.