(Diethylamino)sulfur trifluoride → 5-(5-Chloro-2-fluoro-phenyl)-3-[4-(2-fluoro-ethyl)-5-thiophen-2-yl-4H-[1,2,4]triazol-3-ylsulfanylmethyl]-[1,2,4]oxadiazole

To a cooled (−15° C.) solution of 2-{3-[5-(5-chloro-2-fluoro-phenyl)-[1,2,4]oxadiazol-3-ylmethylsulfanyl]-5-thiophen-2-yl-[1,2,4]triazol-4-yl}-ethanol (46 mg, 0.11 mmol) in anhydrous THF (15 ml) was dropwise added DAST (32 ml, 0.24 mmol). The mixture was stirred at room temperature for 1.5 h and was then quenched with MeOH (1 ml). The solvent was removed under reduced pressure and the residue was partitioned between brine and EtOAc. The aqueous layer was extracted with EtOAc (2×20 ml). The combined organic layers were washed with brine (10 ml), dried (MgSO4) and concentrated under reduced pressure. Purification by flash chromatography (EtOAc:heptane 2:1) and preparative HPLC afforded the title compound as a white solid (11 mg, 22%). 1H NMR (CDCl3) d (ppm): 8.05 (dd, 1H), 7.52 (m, 3H), 7.20 (m, 1H), 7.16 (m, 1H), 4.75 (t, 1H), 4.63 (m, 3H), 4.45 (m, 2H).