In an oven-dried 250 mL round-bottomed flask was dissolved diisopropylamine (1.7 mL, 12 mmol) in tetrahydrofuran (40 mL) to give a colorless solution under nitrogen. After cooling to −30° C., n-BuLi (4.3 mL, 11 mmol) was added, and the mixture was briefly warmed up to rt for 3 min. After cooling down to −78° C., 2-bromopyrazine (0.98 mL, 10.7 mmol) was added dropwise via syringe. The resulting yellow solution was stirred at −78° C. for 5 min. (R,E)-N—((S)-2-(2,3-difluorophenyl)hex-5-enylidene)-2-methylpropane-2-sulfinamide (2.089 g, 6.67 mmol) in 4 mL anhydrous tetrahydrofuran (plus 3 mL rinse) was added via canuula, and the mixture was stirred for 2 h at −75° C. The reaction was quenched with saturated sodium bicarbonate solution and diluted with ethyl acetate. The layers were separated. The aqueous layer was extracted with ethyl acetate. The combined organic layers were washed with brine, dried, and concentrated to give a tan oil. Flash column chromatography up to 80% ethyl acetate/hexane afforded the desired product (1.964 g, 62%) as a dense tan oil: 1H NMR (400 MHz, CHLOROFORM-d) δ ppm 8.33 (d, J=2.26 Hz, 1H) 8.26 (d, J=2.26 Hz, 1H) 6.99-7.22 (m, 3H) 5.74 (d, J=6.53 Hz, 1H) 5.18 (dd, J=9.29, 5.27 Hz, 1H) 4.85-4.99 (m, 2H) 4.30 (d, J=9.54 Hz, 1H) 3.66-3.77 (m, 1H) 2.17 (br. s., 1H) 1.80-2.04 (m, 3H) 1.05 (s, 9H); 19F NMR (376 MHz, CHLOROFORM-d) δ ppm −138.41 (d, J=15.61 Hz, 1F) −144.20-−143.20 (m, 1F); 13C NMR (101 MHz, CHLOROFORM-d) δ ppm 155.19 (s, 1C) 151.32-149.72 (dd, J=13.87 and 249.47 Hz, 1C) 150.24-147.67 (dd, J=12.72 and 246.95 Hz, 1C) 142.89 (s, 1C) 141.44 (br. s., 1C) 140.47 (s, 1C) 136.93 (d, J=10.02 Hz, 1C) 127.54 (d, J=10.79 Hz, 1C) 124.12-124.96 (m, 1C) 123.41-123.97 (m, 1C) 115.23-115.83 (m, 1C) 115.09 (s, 1C) 59.93-60.56 (m, 1C) 56.10-56.69 (m, 1C) 40.72-41.81 (m, 1C) 30.81 (s, 1C) 30.34 (br. s., 1C) 21.94 (q, J=6.17 Hz, 3C).
