Reaction Steps
A solution of N-cyclobutyl-2-(4-(2,4-difluorophenoxyl)piperidin-1-yl)-5,6,7,8-tetrahydropyrido[3,4-b]pyrazin-3-amine TFA salt (144 mg, 0.272 mmol) in DCM (2.72 mL) at 0° C. was treated with pyridine (66.0 μL, 0.816 mmol), followed by acetic anhydride (51.3 μL, 0.544 mmol). The reaction mixture was stirred at 0° C. for 2 h. The reaction mixture was concentrated under reduced pressure and taken up in MeOH, filtered through a 0.45 μm Millipore® syringe filter, and purified via HPLC Method A to give the title compound, as a TFA salt, as a yellow solid (74.9 mg, 48.2%). 1H NMR (500 MHz, methanol-d4, mixture of rotamers) δ ppm 1.82 (m, 2H), 1.97 (m, 2H), 2.11 (m, 4H), 2.19 (s, 1.1H), 2.21 (s, 1.9H), 2.45 (m, 2H), 2.73 (t, J=5.9 Hz, 0.7H), 2.84 (t, J=5.9 Hz, 1.3H), 3.11 (m, 2H), 3.47 (m, 2H), 3.81 (t, J=5.9 Hz, 1.3H), 3.85 (t, J=5.9 Hz, 0.7H), 4.40 (m, 1H), 4.49 (m, 1H), 4.59 (s, 0.7H), 4.63 (s, 1.3H), 6.87 (m, 1H), 6.97 (ddd, J=11.2, 8.5, 3.2 Hz, 1H), 7.17 (td, J=9.2, 5.6 Hz, 1H); ESI-MS m/z [M+H]+ 458.00.
