[CH2:1]([O:8][CH2:9][CH2:10][CH2:11][CH2:12][O:13][C:14]1[N:19]=[C:18]([NH:20][C:21](=[O:26])C(C)(C)C)[C:17]([CH2:27][CH2:28]C(OCC)=O)=[CH:16][CH:15]=1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.Cl.C([O-])([O-])=O.[K+].[K+]>O1CCOCC1>[CH2:1]([O:8][CH2:9][CH2:10][CH2:11][CH2:12][O:13][C:14]1[N:19]=[C:18]2[C:17]([CH2:27][CH2:28][C:21](=[O:26])[NH:20]2)=[CH:16][CH:15]=1)[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1To a solution of intermediate 9 (1.76 g, 3.9 mmol) in 1,4-dioxane (14 mL) was added 3N HCl (7.1 mL) and the mixture was then heated to reflux for 3 h. The mixture was cooled to rt and then anhydrous K2CO3 was slowly added to neutralize the reaction mixture to pH=8, then extracted with EtOAc. The combined organic layers were washed with water, brine, dried over anhydrous Na2SO4 and concentrated in vacuo. The crude product was purified by flash chromatography on silica gel column (elution with PE/EtOAc=4:1-1:1) to give 7-(4-(benzyloxy)butoxy)-3,4-dihydro-1,8-naphthyridin-2(1H)-one (intermediate 10) (671 mg, 54%) as an oil.
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