Iodine-Mediated Fluorination of Alkenes with an HF Reagent: Regioselective Synthesis of 2-Fluoroalkyl Iodides
Tsugio Kitamura*, Ryuichi Komoto, Juzo Oyamada, Masahiro Higashi and Yosuke Kishikawa
*Department of Chemistry and Applied Chemistry, Saga University, Honjo-machi, Saga 840-8502, Japan, Email: kitamuracc.saga-u.ac.jp
T. Kitamura, R. Komoto, J. Oyamada, M. Higashi, Y. Kishikawa, J. Org. Chem., 2021, 86, 18300-18303.
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Iodofluorination of aliphatic and aromatic alkenes with iodine and HF·pyridine complex (pyr·9HF) was performed under mild conditions in the presence of K2S2O8 or Na2S2O8 as oxidants. Substitution reactions of the iodofluorinated products by nitrogen, sulfur, and oxygen nucleophiles enable further applications as a building blocks for synthesis of 2-fluoroalkyl-substituted compounds.
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General Procedure for Iodofluorination of Alkenes Using Na2S2O8 as Oxidant
In a Teflon tube I2 (1.0 mmol, 254 mg, 0.33 M) was dissolved in DCM (2 mL), and pyr•9HF (0.78 mL, 30 mmol for HF) was added. After stirring for 15 min at room temperature, Na2S2O8 (1.0 mmol, 238 mg, 0.33 M) was added, followed by addition of DCM (1 mL) for washing the wall of the tube. Finally, an alkene substrate (1 mmol, 0.33 M) was added, and the mixture was stirred at room temperature for 1 or 24 h. The reaction mixture was quenched with saturated NaHCO3 and Na2SO3. The product was extracted with DCM (20 mL x 3) and washed with saturated NaCl. The organic phase was dried over anhydrous Na2SO4 and concentrated under reduced pressure. The product was purified by column chromatography on silica gel using hexane or hexane/EtOAc as eluent.
iodination, fluorination, sodium peroxydisulfate