1-(Trifluoromethyl)-1,2-benziodoxol-3(1H)-one

Abstract

[887144-94-7] C8H4F3IO2 (MW 316.02) InChI = 1S/C8H4F3IO2/c9-8(10,11)12-6-4-2-1-3-5(6)7(13)14-12/h1-4H InChIKey = XHEOXSQMBWJOKP-UHFFFAOYSA-N (reagent used for direct electrophilic trifluoromethylation1) Physical Data: mp 122.4–123.4 °C (decomposition accompanied by gas evolution). Solubility: sol in polar organic solvents (CH2Cl2, CHCl3, MeCN, MeOH, EtOH, acetone). Form Supplied in: colorless, crystalline solid. Not commercially available. Analysis of Reagent Purity: Anal. calcd (%) for C8H4F3IO2: C, 30.41; H, 1.28. Found: C, 30.56; H, 1.11. 1H NMR (250 MHz, CDCl3, 25 °C): δ = 7.26–7.85 (m, 3H; CHarom), 8.43–8.47 ppm (m, 1H; CHarom ortho to I). 13C NMR (63 MHz, CDCl3, 25 °C): δ = 107.1 (q, JC,F = 380.2 Hz; CF3), 114.8 (q, JC,F = 1.3 Hz; CI), 127.2 (q, JC,F = 3.1 Hz; CH ortho to CI), 131.9 (s; CH and CCO2), 133.7, 135.7 (CH), 165.9 ppm (CO). 19F NMR (188 MHz, CDCl3, 25 °C): δ = −33.8 ppm (s, JC,F = 380.2 Hz, as calculated from the 13C satellites; CF3). IR (CHCl3): v = 3621 (m), 3018 (m), 1660 (s), 1563 (w), 1444 (w), 1316 (w), 1220 (s), 1213 (s), 1158 (s), 1077 cm−1 (s). Preparative Methods: (1) 2-Iodobenzoic acid (25.3 g, 0.102 mol) was suspended in 300 mL of water, NaIO4 (49.0 g, 0.229 mol) was added in one portion, and the mixture was refluxed for 18 h. 100 mL of water and 3 mL of conc. H2SO4 were added and stirring was continued for 30 min. The precipitate was filtered off, washed with water (4 × 20 mL), and dried under reduced pressure to give 25.8 g (96%) of 1-hydroxy-1,2-benziodoxol-3-(1H)-one. mp 235°C (violent decomposition). 1-Hydroxy-1,2-benziodoxol-3-(1H)-one (6.00 g, 21.1 mmol) was refluxed in Ac2O (15 mL) for a few minutes until a clear solution was obtained. Upon cooling, white crystals began to separate and cooling was continued to −20 °C for 4 h. The solution was decanted and the crystals were dried under vacuum for 24 h under stirring. The resulting white powdery material was identified as 1-acetoxy-1,2-benziodoxol-3-(1H)-one. mp 162–165 °C. The powdered 1-acetoxy-1,2-benziodoxol-3-(1H)-one was dissolved in dry MeCN (50 mL) under argon. TMSCF3 (4.5 mL, 30.4 mmol) followed by dry CsF (0.05 g, 0.33 mmol) was added and the suspension was vigorously stirred at room temperature for 22 h. The solvent was evaporated under reduced pressure and the brown residue was purified by column chromatography (SiO2, CH2Cl2/MeOH = 15:1 v/v) giving 5.65 g of the title compound (79% yield over two steps, 76% from 2-iodobenzoic acid) (eq 1). mp 122–123 °C (decomposition).2, 3 Purification: flash column chromatography (SiO2, CH2Cl2/MeOH = 15/1) or sublimation (rt, HV, 1–2 days). Handling, Storage, and Precautions: the pure substance is stable at room temperature under air over several months. Due to violent decomposition (to mainly CF3I), it should not be heated beyond its melting point as a solid. Minor decomposition to trifluoromethyl 2-iodobenzoate and 2-iodobenzoyl fluoride has been observed after purification by recrystallization from acetonitrile. The title compound is incompatible with strong acids, strong bases, reducing agents, and THF (polymerization). Toxicity studies are lacking; therefore, appropriate precautions are strongly recommended.