We report a simple protocol for (ethoxycarbonyl)difluoromethylthiolation of nucleophilic compounds using a difluoroalkyl sulfonium salt which can be in situ prepared via Tf2O triggered electrophilic activation of a benzyl difluoroalkyl sulfoxide. With the protocol, difluoroalkylthiolated arenes, heteroarenes and α-difluoroalkylthiolated carbonyl compounds etc. were obtained smoothly with good to excellent yields. Merits of the reaction include the readily available difluoroalkylthiolation reagent and substrates, mild conditions, and excellent regioselectivity.
Unless otherwise indicated, all glassware was oven dried by a heat air gun before use and all reactions were performed under an atmosphere of nitrogen. All solvents were distilled from appropriate drying agents prior to use. All reagents were used as received from commercial suppliers unless otherwise stated. Reaction progress was monitored by thin layer chromatography (TLC) performed on plastic plates coated with silica gel GF254 with 0.2 mm thickness. Chromatograms were visualized by fluorescence quenching with UV light at 254 nm or by staining using potassium permanganate. Flash column chromatography was performed using silica gel 60 (160-200 mesh). Neat infra-red spectra were recorded using a NEXUS670 FT-IR spectrometer. Wavelengths (ν) are reported in cm-1. Mass spectra were obtained using a TOF MS instrument. All 1H NMR, 13C NMR spectra were recorded on Bruker AV-400 or AV-600.Chemical shifts were reported in parts per million (ppm), and the residual solvent peak was used as an internal reference: proton (chloroform δ 7.26), carbon (chloroform δ 77.16). Multiplicity was indicated as follows: s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet), dd (doublet of doublet). Coupling constants were reported in Hertz (Hz).
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