关键词: 二氟卡宾, 硫代氟光气, 三氟甲硫基化, 芳基碘化物, 烯基碘化物

Difluorocarbene has found widespread applications in the synthesis of fluorine-containing molecules. We have previously found that difluorocarbene can react with elemental sulfur to produce thiocarbonyl fluoride, which is of great value for the new discoveries of difluorocarbene chemistry and the investigations of synthetic utilities of thiocarbonyl fluoride. We have developed the transformation of difluorocarbene into thiocarbonyl fluoride as a synthetic tool to achieve trifluoromethylthiolation of terminal alkynes and alkyl halides. In continuation of our research interest in this chemistry, herein we further apply the difluorocarbene transformation to the trifluoromethylthiolation of aryl and alkenyl iodides. Trifluoromethylthiolation is an active research area in organofluorine chemistry, and the commonly used trifluoromethylthiolation methods usually require the use of expensive CF₃S-containing reagents. In contrast, in our protocol the CF₃S group is generated in situ from difluorocarbene, elemental sulfur and a fluoride anion, all of which are cheap and easily available reagents. The general experimental procedure is shown as follows. Into a 5 mL sealed tube were added 4-phenyl phenyl iodide (1a, 56.0 mg, 0.2 mmol), S (57.8 mg, 1.8 mmol), Ph₃P⁺CF₂CO₂^– (PDFA) (213.8 mg, 0.6 mmol), AgF (0.5 mmol, 63.4 mg), ligand L₁ (0.6 mmol, 158.9 mg), CuI (76.2 mg, 0.4 mmol), and dioxane (1.0 mL) under a N₂ atmosphere. The reaction mixture was stirred at 110 ℃ for 8 h. After the reaction system was cooled to room temperature, Et₃N (0.5 mL) was added to remove the excess elemental sulfur by a redox reaction (the final product would be contaminated by elemental sulfur if elemental sulfur was not removed). The mixture was diluted with 10 mL of saturated brine, and then the product was extracted with ethyl acetate. The combined organic layers were washed with brine, dried over sodium sulfate, and concentrated to 1 mL. The residue was subjected to flash column chromatography to afford the pure product.

Key words: difluorocarbene, thiocarbonyl fluoride, trifluoromethylthiolation, aryl iodide, alkenyl iodide