To a solution of 4-(5-oxo-3-phenyl-5,6-dihydro-1,6-naphthyridin-2-yl)benzaldehyde (186 mg, 0.57 mmol) in dry DMF (2 mL) was added 60% sodium hydride in mineral oil (29 mg, 0.72 mmol). The reaction was stirred at room temperature for 15 minutes and then methyl iodide was added via syringe (40 μL, 0.70 mmol). After 30 minutes the reaction was diluted with ethyl acetate and some acetic acid was added to neutralize the base. The solution was washed with aqueous NaHCO3 and the organic layer was dried (anhydrous Na2SO4), filtered and the solvent evaporated. The residue was triturated with diethyl ether to give the title compound as a pale yellow solid. The mother liquors were chromatographed on silica gel eluting with a 30-70% ethyl acetate/hexane gradient to give additional product. 1H-NMR (500 MHz, CDCl3): δ 10.02 (1H, s), 8.74 (1H, s), 7.80 (2H, d, J=8 Hz), 7.60 (2H, d, J=8 Hz), 7.37 (1H, d, J=7.6 Hz), 7.28-7.31 (2H, m), 7.19-7.22 (2H, m), 6.85 (1H, d, J=7.6 Hz), 3.67 (3H, s). m/e (m+1): 341.1.
