Meerwein’s Reagent Mediated, Significantly Enhanced Nucleophilic Fluorination on Alkoxysilanes

Abstract

We developed a new facile method to fluorosilanes from alkoxysilanes using Meerwein’s reagent. Our protocol afforded fluo­rosilanes in excellent yields in various organic solvents including acetonitrile under mild reaction conditions at room temperature. We also proposed a reaction mechanism with the probable silyloxonium intermediates.

Key words

Meerwein’s reagent - nucleophilic fluorination - silyl­oxonium - fluorine - silicon

• References and Notes

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• 30 Typical Procedure for the Synthesis of Fluorosilanes: A dry and nitrogen-flushed 10 mL screw-capped vial was charged with alkoxysilane (1, 1.0 mmol), MeCN (5.0 mL) followed by the addition of Me₃OBF₄ (147.9 mg, 1.0 mmol) or Et₃OBF₄ (189.9 mg, 1.0 mmol). The reaction mixture was stirred at 50 °C for 30 min and quenched by dropwise addition of H₂O. It was then diluted with CH₂Cl₂; the organic layer was washed with brine, dried over anhyd MgSO₄, and evaporated under reduced pressure. The crude mixture was purified by chromatography on silica gel (5% EtOAc–hexane as eluent) to give the corresponding fluorosilane as a colorless liquid.(4-Bromophenyl)di(prop-2-enyl)fluorosilane (2a): colorless liquid. ¹H NMR (270 MHz, CDCl₃): δ = 1.96–2.01 (m, 4 H), 4.97–5.06 (m, 4 H), 5.70–5.86 (m, 2 H), 7.44 (d, J = 8.1 Hz, 2 H), 7.56 (d, J = 8.1 Hz, 2 H). ¹³C NMR (68 MHz, CDCl₃): δ = 21.0, 21.2, 116.3, 125.6, 130.8, 130.85, 131.2, 135.06, 135.09. ¹⁹F NMR (376 MHz, CDCl₃): δ = –171.93. HRMS (FAB⁺): m/z [M – H]⁺ calcd for C₁₂H₁₃BrFSi: 282.9954; found: 282.9935.Fluoro[phenyldi(prop-2-enyl)]silane (2b): colorless liquid. ¹H NMR (270 MHz, CDCl₃): δ = 1.98–2.04 (m, 4 H), 4.97–5.06 (m, 2 H), 5.74–5.89 (m, 2 H), 7.38–7.50 (m, 3 H), 7.58–7.62 (m, 2 H). ¹³C NMR (68 MHz, CDCl₃): δ = 21.1, 21.3, 115.9, 128.0, 130.6, 131.3, 133.5, 133.6. ¹⁹F NMR (470 MHz, CDCl₃): δ = –172.82. HRMS (FAB⁺): m/z [M – H]⁺ calcd for C₁₂H₁₅FSi: 206.0927; found: 206.0921.Fluoro[diphenyl(prop-2-enyl)]silane (5): colorless liquid. ¹H NMR (400 MHz, CDCl₃): δ = 2.22–2.25 (m, 2 H), 4.95–5.04 (m, 2 H), 5.79–5.86 (m, 1 H), 7.38–7.47 (m, 6 H), 7.61–7.63 (m, 4 H). ¹³C NMR (100 MHz, CDCl₃): δ = 21.7, 21.8, 116.2, 128.0, 130.7, 131.2, 132.7, 132.8, 134.25, 134.27. ¹⁹F NMR (376 MHz, CDCl₃): δ = –170.8. HRMS (EI⁺): m/z [M]⁺ calcd for C₁₅H₁₅FSi: 242.0927; found: 242.0927.Fluorotri(prop-2-enyl)silane (7): colorless liquid. ¹H NMR (400 MHz, CDCl₃): δ = 1.76–1.79 (m, 6 H), 4.97–5.02 (m, 6 H), 5.75–5.82 (m, 3 H). ¹³C NMR (100 MHz, CDCl₃): δ = 20.5, 20.7, 115.6, 131.4. ¹⁹F NMR (376 MHz, CDCl₃): δ = –170.2. CAS registry no. 429-89-0
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