A solution of tert-butyl N-tert-butoxycarbonyl-N-[3-[3-[4-(chloromethyl)phenyl]isoxazol-5-yl]-5-(4-isopropylsulfonylphenyl)pyrazin-2-yl]carbamate 9 (4.1 g, 6.127 mmol), 4-aminotetrahydro-2H-pyran (2.479 g, 24.51 mmol), KI (1.017 g, 324.9 μL, 6.127 mmol) and DIPEA (791.9 mg, 1.067 mL, 6.127 mmol) in DMF (51 mL) was stirred at 40° C. for 3 h then stirred overnight at rt. The mixture was slowly poured onto a stirred ice/water mixture (400 ml) and stirred at rt overnight. The mixture was filtered and washed with water to give a wet paste which was dissolved in warm EtAc (500 ml), washed with water then brine, dried over MgSO4 and concentrated under reduced pressure to give a yellow foam. The above material was dissolved into DCM (40 mL) and treated at RT with TFA (8 mL, 103.8 mmol). The mixture was stirred for 1 h at RT, then concentrated under reduced pressure. The residue was azeotroped three times with a DCM/MeOH yielding a yellow solid that was stirred in a mixture of ethanol (50 mL) and water (50 mL). Excess potassium carbonate (20 mL of 0.5 M, 10 mmol) was added and the mixture was stirred for 45 min at RT. The solid was filtered off, washed with water and dried under high vacuum at 77° C. to give 5-(4-isopropylsulfonylphenyl)-3-[3-[4-[(tetrahydropyran-4-ylamino)methyl]phenyl]isoxazol-5-yl]pyrazin-2-amine (2.857 g, 5.354 mmol) as a free base.
