To a solution of 3-bromo-5-((1 S,3S,4S)-4-((tert-butyldimethylsilyl)oxy)-3-fluorocyclohexyl)pyrazin-2-amine (760.0 g, 1879.4 mmol) and tert-butyl 2-fluoro-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate (605.5 g, 1879.4 mmol) in DME (3.0 kg) was added 2.0 M aqueous Na2CO3 (1880 mL, 3760 mmol) and Pd(dppf)Cl2.DCM (38.4 g, 47.0 mmol). After degassing with N2 three times, the reaction mixture was heated to reflux (79-80° C.) and stirred at this temperature for 3 hours. The reaction temperature was cooled to room temperature and MTBE (2.5 kg) was added followed by water (4.0 kg). The mixture was stirred for 10 minutes before phase separation, and the aqueous layer was extracted with MTBE (1.8 kg). The combined organic layers were washed with water (2×4 kg), and concentrated under vacuum at 30-40° C. to give crude product tert-butyl 4-(3-amino-6-((1S,3S,4S)-4-((tert-butyldimethylsilyl)oxy)-3-fluorocyclohexyl)pyrazin-2-yl)-2-fluorobenzoate (ca. 1 kg). The mixture of this crude product and EtOH (95%, 3.2 kg) was heated to reflux (78-80° C.) for 30 minutes to give a solution. The temperature was cooled to 40° C. within 100 minutes followed by addition of water (800 g) within 30 minutes. The temperature was cooled to ˜5° C. within 100 minutes and stirring at this temperature was continued for a further 60 minutes. The solid precipitation was filtered and the wet cake was washed with EtOH/water (1.2 L, 5/1, vol/vol). After drying under vacuum at 50° C. for 5 hours, tert-butyl 4-(3-amino-6-((1 S,3S,4S)-4-((tert-butyldimethylsilyl)oxy)-3-fluorocyclohexyl)pyrazin-2-yl)-2-fluorobenzoate was obtained as a brown powder (755 g, 76.4% yield over 2 steps, assay purity is 98.8%). mp 169-172° C. ESI-MS (m/z): 520.2739 ([M+H]+, 100). HPLC (method A) retention time 15.76 min. 1H NMR (400 MHz, CDCl3): 7.98 (t, J=8 Hz, 1H), 7.91 (s, 1H), 7.61 (d, J=8 Hz, 1H), 7.55 (d, J=8 Hz, 1H), 4.68 (br. s, 2H), 4.42-4.48, 4.30-4.36 (m, 1H), 3.67-3.76 (m, 1H), 2.75-2.83 (m, 1H), 2.28-2.36 (m, 1H), 1.98-2.05 (m, 1H), 1.83-1.92 (m, 2H), 1.46-1.68 (m, 2H), 1.62 (s, 9H), 0.92 (s, 9H), 0.11 (d, J=8 Hz, 6H).
