A vial was charged with (3S)-2-[(4-bromo-2-fluoro-phenyl)methyl]-3-methyl-6-phenyl-thiazinane 1,1-dioxide (250 mg, 0.61 mmol), 4-(1,2,4-triazol-4-yl)piperidine hydrochloride (172 mg, 0.91 mmol), cuprous iodide (35 mg, 0.18 mmol), N,N-dimethylglycine (38 mg, 0.36 mmol) and tetrabutylphosphonium malonate (1.3 g, 1.9 mmol) and the vial was purged with nitrogen for. Dimethyl sulfoxide (3 mL) was then added and the vial was purged with nitrogen for an additional 2 minutes. The reaction mixture was then sonicated for 5 minutes and stirred at 45° C. for 20 hours. The DMSO solution was then directly purified by preparative HPLC to give (3S)-2-[[2-fluoro-4-[4-(1,2,4-triazol-4-yl)-1-piperidyl]phenyl]methyl]-3-methyl-6-phenyl-thiazinane 1,1-dioxide Stereoisomer A (109 mg, 0.23 mmol, 37% yield) as a white solid. 1H NMR (400 MHz, DMSO) δ 8.66-8.62 (s, 2H), 7.49-7.43 (m, 2H), 7.43-7.29 (m, 4H), 6.87-6.82 (m, 1H), 6.80-6.73 (m, 1H), 4.49-4.24 (m, 4H), 4.15-4.04 (m, 1H), 3.90-3.80 (m, 2H), 2.89-2.77 (m, 2H), 2.47-2.35 (m, 1H), 2.15-2.04 (m, 3H), 2.04-1.89 (m, 2H), 1.88-1.74 (m, 1H), 1.70-1.60 (m, 1H), 1.14-1.05 (d, J=6.9 Hz, 3H); LCMS [M+1]+=484.2.
