Reaction Steps
2-(4-(Bromomethyl)-3-fluorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane was prepared in three steps from 4-bromo-2-fluoro-1-methylbenzene following the procedure of White, J. R., et al., Tetrahedron Leu. 2010, 51, 3913-3917. In a dry round bottom flask equipped with a stir bar and septum, 2H-benzo[b][1,4]thiazin-3(4H)-one (90 mg, 0.545 mmol), 2-(4-(bromomethyl)-3-fluorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (150 mg, 0.476 mmol), and potassium carbonate (90 mg, 0.652 mmol) were massed. The flask was purged with argon then charged with dry DMF (3 mL). The reaction was stirred at 60° C. and monitored by LCMS. After 3 h, reaction was deemed to be complete and cooled to room temperature. The reaction was diluted with ethyl acetate (20 mL), and the organic layer was washed with saturated NaHCO3. The two layers were separated and the aqueous layer was extracted with ethyl acetate (3×20 mL). The organic extracts were combined then washed with saturated LiCl solution (20 mL) and brine (20 mL). The organic portion was dried over MgSO4, filtered, and concentrated in vacuo. The crude residue was purified by flash column chromatography on silica gel, eluting with hexanes/ethyl acetate to afford 4-(2-fluoro-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)-2H-benzo[b][1,4]thiazin-3(4H)-one. In a 5-mL conical microwave vial with a stir bar, 4-(2-fluoro-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)-2H-benzo[b][1,4]thiazin-3(4H)-one (40 mg, 0.100 mmol), 4-bromo-1-methyl-1H-pyrazole (20 mg, 0.124 mmol), Cs2CO3 (70 mg, 0.215 mmol), and PdCl2(dppf).DCM (10 mg, 0.012 mmol) were massed. The vial was then charged with THF/H2O (5:1, 3 mL) and sealed with a crimped cap. The reaction was heated to 150° C. for 30 minutes. The reaction was cooled to room temperature, diluted with ethyl acetate (10 mL) and brine (10 mL). The layers were separated and the aqueous layer was extracted with ethyl acetate (3×15 mL). The organic layers were combined, dried over MgSO4, filtered and concentrated in vacuo. The crude residue was purified on a preparative Phenomenex Luna C18 column using 0.1% TFA in H2O/acetonitrile as a mobile phase. The desired fractions were combined and concentrated to afford the title compound. LCMS: RT=0.728, >98% @ 254 nm, >98% @ 215 nm; m/z (M+H)+=354. 1H NMR (400 MHz, CDCl3, δ (ppm)): 7.69 (s, 1H), 7.56 (s, 1H), 7.36 (d, J=7.6 Hz, 1H), 7.15-7.12 (m, 3H), 7.06-6.97 (m, 3H), 5.27 (s, 2H), 3.92 (s, 3H), 3.52 (s, 2H); HRMS calculated for C19H17N3OSF (M+H)+ m/z: 354.1076, measured: 354.1076.
