To a suspension of triazolone 7 (0.11 g, 0.3 mmol) in dimethylsulfoxide (4 mL) was added K2CO3 (0.08 g, 0.6 mmol). The resulting mixture was stirred at room temperature for 1 h. After the addition of 2-bromo butane (0.05 mL, 0.45 mmol), the temperature increased to 80° C. for overnight. After cooling to room temperature, the reaction mixture was diluted with water and extracted with dichlormethane. The combined organic layer was dried over Na2SO4, filtered, and concentrated to yield the crude product, which was purified by column chromatography to obtain triazolone 8 (0.11 g, 87%). 1H NMR (400 MHz, CDCl3, δH): 7.64 (s, 1H), 7.37 (dd, J=13.0, 2.2 Hz, 1H), 7.26-7.24 (m, 1H), 7.04 (t, J=8.8 Hz, 1H), 6.99-6.97 (m, 2H), 6.88-6.84 (m, 2H), 4.31-4.26 (m, 1H), 3.77 (s, 3H), 3.26 (bs, 8H), 1.86-1.81 (m, 1H), 1.73-1.71 (m, 1H), 1.38 (d, J=6.8 Hz, 3H), 0.89 (t, J=7.4 Hz, 3H). 13C NMR (100 MHz, CDCl3, δC): 154.6, 154.2, 151.6, 139.4, 133.3, 128.4, 119.4, 118.7, 118.0, 114.5, 111.0, 110.8, 55.6, 52.8, 51.0, 50.5, 28.4, 19.3, 10.8.
