[CH2:1]([N:8]1[CH2:13][CH2:12][C:11](=O)[CH2:10][CH2:9]1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[C:15]([NH2:21])(=[O:20])[CH2:16][C:17]([CH3:19])=O.C([O-])(O)=O.[Na+]>CS(O)(=O)=O.O=P12OP3(OP(OP(O3)(O1)=O)(=O)O2)=O.O.C(Cl)Cl>[CH2:1]([N:8]1[CH2:13][CH2:12][C:11]2[N:21]=[C:15]([OH:20])[CH:16]=[C:17]([CH3:19])[C:10]=2[CH2:9]1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1A mixture of 1-benzyl-4-piperidone (19.6 mL, 106 mmol), acetoacetamide (11.7 g, 116 mmol) in Eaton's reagent (40 mL) was allowed to stir at 110° C. After stirring for 18 h, the reaction mixture was cooled to rt, and then slowly poured into stirred aq NaHCO3 (150 g of NaHCO3 in 1000 mL of water. The mixture was diluted with DCM (1000 mL) and H2O (50 mL), and the two phases were separated. The products were extracted once with DCM (500 mL) from the aqueous layer. The combined organic layer was washed with brine (500 mL), dried over Na2SO4, filtered, and concentrated under reduced pressure. The brown residue was triturated with acetone (200 mL). The precipitated solid was collected on a funnel, washed with acetone (100 mL), and dried under reduced pressure to give 6-benzyl-4-methyl-5,6,7,8-tetrahydro-1,6-naphthyridin-2-ol. 1H NMR (400 MHz, CDCl3) δ ppm 12.71 (br s, 1 H), 7.26-7.35 (m, 5 H), 6.22 (s, 1 H), 3.71 (s, 2 H), 3.34 (s, 2 H), 2.70-2.73 (m, 2 H), 2.77-2.79 (m, 2 H), 2.03 (s, 3 H); MS (ESI+) m/z 255.42 (M+H)+.
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