To a 100° C. solution of (S)-4-(5-bromo-2,4-difluorophenyl)-4-methyl-5,6-dihydro-4H-1,3-thiazin-2-amine (12.6 g, 29.9 mmol, 1 equiv) in 1,2-dimethoxyethane:water:ethanol (15:7:5, 300 mL) is added a pyrimidine-5-boronic acid (25 g, 203 mmoles, 6.8 equiv) followed by cesium carbonate (58 g, 180 mmoles, 6 equiv) and bis(triphenylphosphine)palladium(II) chloride (4.2 g, 6.0 moles, 0.2 equiv). After 40 minutes, the reaction is cooled to ambient temperature, diluted with water, and extracted with ethyl acetate. The organic phase is dried over magnesium sulfate, filtered, and concentrated under reduced pressure. The residue is purified by silica gel chromatography eluting with a step gradient of hexanes:ethyl acetate (7:3) to hexanes:ethyl acetate (1:1) to give the title compound (67% yield): MS (m/z): 421 (M+1).
