All reagents and solvents were purchased from Aldrich and Merck were used without further purification. The 1H and 13C NMR spectra were obtained on Bruker with DMSO as a solvent (1H NMR at 300 MHz and 13C NMR at 75 MHz). In the 19F-NMR spectra (282 MHz), up field shifts were quoted as negative and referenced to CFCl3. Mass spectra were taken by a Micro mass Platform II: EI mode (70 eV).
General procedure for the preparation of 2-(tetrafluoropyridin-4-yl)-1,2,3-triazole
A mixture of chalcone (1 mmol), sodium azide (1 mmol) and CuO (2.5 mol%) were stirred in DMF (3 mL) for 20 h at 100 °C. After completion of the reaction as indicated by TLC pentafluoropyridine (1 mmol) was added to the mixture and the reaction continued at 100 °C for 5 h. Following, to the reaction mixture was added water 4 mL, and extracted with ethyl acetate and dichloromethane (3 × 5 mL). The solvent was removed in vacuo, and the crude product was purified by column chromatography using ethyl acetate/n-hexane (2/10) to give the pure product.
(2-(Perfluoropyridin-4-yl)-5-phenyl-2H-1,2,3-triazol-4-yl)(phenyl)methanone (2a)
(0.24 g, 65 %) as brown solid; mp 240–245 °C decompose. 1H NMR (DMSO): δ (ppm) 7.96–8.41 (10H, m, Ar–H); 19F NMR (DMSO): δ (ppm) −89.5 (2F, m, JFF 23, F-2,6), −144.8 (2F, m, JFF 20, F-3,5); 13C NMR (DMSO): δ (ppm) 126.81, 126.96, 127.40, 128.14, 128.18, 128.24, 128.29, 128.66, 128.74, 128.86, 128.92, 129.23, 129.44, 129.52, 129.77, 129.86, 170.31 ppm. MS (EI), m/z (%) = 415 [M+NH3]+, 399 (M), 384, 360, 343, 316, 286, 268, 248, 220, 199, 169, 141, 119, 101, 86, 58, 42.
(5-(4-Methoxyphenyl)-2-(perfluoropyridin-4-yl)-2H-1,2,3-triazol-4-yl)(phenyl)methanone (2b)
(0.20 g, 60 %) as a yellow solid; mp 265–270 °C decompose. 1H NMR (DMSO): δ (ppm) 4.5 (3H, OCH3) 7.60–8.61 (10H, m, Ar–H); 19F NMR (DMSO): δ (ppm) −95.0 (2F, m, F-2,6), −153.0 (2F, m, F-3,5); 13C NMR (DMSO): δ (ppm) 114.29, 115.54, 121.54, 122.94, 123.23, 127.82, 130.35, 130.85, 140.85, 141.22, 157.44 ppm. MS (EI), m/z (%) = 427 [M−1], 321, 282, 165, 91.