Synthesis of β-CF₃ Ketones through Copper/Silver Cocatalyzed Oxidative Coupling of Enol Acetates with ICH₂CF₃

Abstract

A simple method for the synthesis of β-CF₃ ketones through copper/silver cocatalyzed oxidative coupling of enol acetates with ICH₂CF₃ has been developed. Enol acetates were chosen as the source of carbonyl group, giving the β-CF₃ ketones in moderate yields. Control experiments imply that a radical process maybe involved in this reaction.

Key words

β-CF₃ ketone - oxidative coupling - radical reaction - enol ­acetate

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• 10 Typical Procedure: To a sealed tube were added enol acetate (0.75 mmol), ICH₂CF₃ (0.5 mmol, 105 mg), Cu(OAc)₂·H₂O (0.05 mmol, 10 mg), Ag₂SO₄ (0.1 mmol, 31 mg), Et₃N (0.5 mmol, 50 mg), TBHP (1.5 mmol, 193 mg, 70% in water), and CH₃CN (1 mL), then the tube was stirred at 100 °C for 24 h. After completion of the reaction, the resulting mixture was diluted with dichloromethane and washed with water. The separated aqueous phase was washed with CH₂Cl₂. The combined organic layers were washed with brine, dried over Na₂SO₄, filtered, and concentrated under vacuo. The crude mixture was purified by column chromatography on silica gel (petroleum ether/ethyl acetate) to afford the desired product 3. 4,4,4-Trifluoro-1-phenylbutan-1-one (3a) Yield: 71 mg (70%); white solid; mp 56–58 °C; ¹H NMR (400 MHz, CDCl₃): δ = 7.98 (d, J= 7.6 Hz, 2 H), 7.61 (t, J= 7.2 Hz, 1 H), 7.49 (t, J= 7.6 Hz, 2 H), 3.27 (t, J= 7.6 Hz, 2 H), 2.66–2.54 (m, 2 H); ¹³C NMR (100 MHz, CDCl₃): δ = 196.3, 136.1, 133.6, 128.8, 128.0, 127.1 (q, J= 274.2 Hz), 31.2 (d, J= 2.9 Hz), 28.3 (q, J = 29.9 Hz); ¹⁹F NMR (376 MHz, CDCl₃): δ = –66.45.