Benzyl bromide was purified by passage through a plug of basic alumina prior to use. A solution of 3-chloro-2-(4-(2,4-difluorophenoxyl)piperidin-1-yl)pyrido[3,4-b]pyrazine (736.2 mg, 1.954 mmol) in ACN (9.77 mL) was divided into two equal portions. Each solution was treated with a half portion of benzyl bromide (232 μL, 1.954 mmol) and stirred at 80° C. for 3 h. The reaction mixtures were allowed to cool to room temperature, and Each solution was treated with a half portion of sodium triacetoxyborohydride (1.242 g, 5.86 mmol). The reaction mixtures were stirred at room temperature for 1 h, then were quenched with saturated aqueous NaCl. The reaction mixtures were combined and partitioned between EtOAc with Et2O added to assist in phase separation and saturated aqueous NaCl. The organic layer was dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography using a 20% to 60% gradient of EtOAc in heptanes gave the title compound (522.2 mg, 56.8%). ESI-MS m/z [M+H]+ 471.4.
