Unexpected Substitution Reaction of 1,1-Dichloro-2,2,2-trifluoroethane (HCFC-123) with Phenolates

Abstract

An unexpected substitution reaction of HCFC-123 with phenolates is reported. During the reaction, fluorine atoms in HCFC-123 are removed one by one in the presence of phenolates.

Key words

dichlorotrifluoroethane - phenolates - elimination - substitution

• References and Notes

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• 19 (2,2-Dichloro-1,1-difluoroethoxy)benzene (2a): Typical Procedure A 20 mL Schlenk tube was charged with DMF (10 mL) and 1a (5 mmol, 470 mg). KOH (5 mmol, 280 mg) was added, and the mixture was stirred at 40 °C until the KOH disappeared. The mixture was then cooled to r.t. Precooled HCFC-123 (10 mmol, 1.52 g) was added to the solution, and the mixture was stirred at 90 °C for 2 h, then cooled to r.t. The mixture was then poured into Et₂O (100 mL), washed with H₂O, dried (Na₂SO₄), and concentrated by rotary evaporation under vacuum. The residue was purified by flash column chromatography [silica gel, PE–CH₂Cl₂ (20:1)] to give a colorless oil; yield: 994 mg (88%). ¹H NMR (300 MHz, CDCl₃): δ = 7.35–7.40 (m, 2 H), 7.21–7.29 (m, 3 H), 5.91 (t, J = 4.4 Hz, 1 H). ¹³C NMR (100 MHz, CDCl₃): δ = 149.5, 129.6, 126.4, 121.7, 119.7 (t, J = 270 Hz), 67.8 (t, J = 42 Hz). ¹⁹F NMR (282 MHz, CDCl₃): δ = –80.2 (d, J = 5.8 Hz). MS (EI): m/z (%) = 226 (M⁺, 21.51), 77 (100), 143 (50.87), 65 (38.96), 94 (30.34), 226 (21.51).