Sodium borohydride → N-(8-chloro-6-methyl-5,6-dihydrobenzo[c][2,7]naphthyridin-2-yl)acetamide

To a stirred solution of 2-acetamido-8-chloro-6-methylbenzo[c][2,7]naphthyridin-6-ium fluoride (2.1 g, 2.47 mmol) in a mixture of THF (20 mL) and MeOH (5 mL) at 0° C. was added NaBH4 (0.199 g, 5.27 mmol) in three portions and the reaction was stirred at rt for 45 min. The volatile organics were removed under reduced pressure; saturated ammonium chloride solution (30 mL) was added and the solution extracted with ethyl acetate (2×30 mL). The combined organic layers were washed with brine (25 mL), dried over sodium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (hexane/ethyl acetate) to afford N-(8-chloro-6-methyl-5,6-dihydrobenzo[c][2,7]naphthyridin-2-yl)acetamide (0.71 g, 2.29 mmol, 93% yield) as a yellow solid. LC/MS (ESI) m/e 288.2 [(M+H)+, calcd for C15H15ClN3O 288.1]; LC/MS retention time (method C); tR=1.87 min; HPLC retention time (method A): tR=12.76 min; HPLC retention time (method B): tR=13.07 min; 1H NMR (400 MHz, DMSO-d6) δ 10.46 (s, 1H), 8.36 (s, 1H), 8.16 (d, J=0.40 Hz, 1H), 7.63 (d, J=8.40 Hz, 1H), 6.88 (dd, J=2.00, 8.00 Hz, 1H), 6.82 (d, J=2.00 Hz, 1H), 4.26 (s, 2H), 2.89 (s, 3H), 2.11 (s, 3H).