[ClH:1].C([N:9]1[CH2:18][CH2:17][C:16]2[N:15]=[C:14]([C:19]([O:21][CH3:22])=[O:20])[CH:13]=[CH:12][C:11]=2[CH2:10]1)C1C=CC=CC=1>CO.[OH-].[Pd+2].[OH-]>[ClH:1].[N:15]1[C:16]2[CH2:17][CH2:18][NH:9][CH2:10][C:11]=2[CH:12]=[CH:13][C:14]=1[C:19]([O:21][CH3:22])=[O:20]The crude methyl 6-benzyl-5,6,7,8-tetrahydro-1,6-naphthyridine-2-carboxylate hydrochloride (1.20 g, 3.76 mmol) was dissolved in MeOH (100 mL) and thoroughly degassed. Palladium hydroxide (0.185 g, 1.32 mmol) was added to the solution before being purged with H2 gas three times. The reaction was allowed to stir at rt for 13 h under 1 atm of H2 gas. The mixture was then filtered through a pad of Celite and rinsed with EtOH. The filtrate was then concentrated down to yield methyl 5,6,7,8-tetrahydro-1,6-naphthyridine-2-carboxylate hydrochloride (0.97 g, 100%). LC-MS: (FA) ES+ 220; 1H NMR (Methanol-d4, 400 MHz) δ 8.05 (d, J=8.0 Hz, 1H), 7.89 (d, J=8.0 Hz, 1H), 4.52 (s, 2H), 3.98 (s, 3H), 3.66 (t, J=6.5 Hz, 2H), 3.33 (m, 2H).
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