Synthesis
The purified alkyne (5 mmol) was treated with a solution of HNTf2 (60-200 mol %) in 1,4-dioxane in apreheated oil bath at 100°C, under magnetic stirring, for 18-52 h, and the corresponding ketone was purified by column chromatography after cooling 4-Chloro-4'-fluorobutyrophenone. The reaction crude was purified by column chromatography using 20% AcOEt in n-hexane as an eluent. Isolated yield: 850 mg (85%). R f (20% AcOEt in n-hexane): 0.66. GC-MS (m/ z, M+? 200), major peaks found: 200 (1%), 164 (1%), 138 (43%), 123 (100%), 107 (10%). 1H NMR (δ, ppm; J, Hz): 8.03-7.97 (2C-H arom, mult), 7.17-7.09 (2C-H arom, mult), 3.68 (CH2, t, J = 6.2), 3.15 (CH2, t, J = 7.0), 2.22 (CH2, tt, J = 7.0, 6.2). 13C NMR (δ, ppm; J, Hz): 197.3 (C=O), 166.1 (C, d, J 1 C-F = 254.7), 133.2 (C, d, J 4 C-F = 4.3), 130.6 (2CH, d, J 3 C-F = 9.3), 115.9 (2CH, d, J 2 C-F = 22.2), 44.6 (CH2), 35.2 (CH2), 26.7 (CH2).
