Cl.Cl.C([C:10]1[C:11]([Cl:21])=[N:12][C:13]2[CH2:14][CH2:15][NH:16][CH2:17][C:18]=2[C:19]=1[CH3:20])C1C=CC=CC=1.CO>C(Cl)Cl.[Cl-].[Na+].O.ClCCCl>[ClH:21].[Cl:21][C:11]1[CH:10]=[C:19]([CH3:20])[C:18]2[CH2:17][NH:16][CH2:15][CH2:14][C:13]=2[N:12]=1To a suspension of crude benzyl-2-chloro-4-methyl-5,6,7,8-tetrahydro-1,6-naphthyridine dihydrochloride (8.00 g, 23.1 mmol) in DCM (100 mL), 2 M Na2CO3aq (50 mL) was added. The mixture was stirred for 20 min, and then diluted with brine. The products were extracted twice with DCM, and the combined organic layer was washed with brine, dried over Na2SO4, filtered, and concentrated to give crude (6.14 g). A solution of the residue and ACEC1 (5.05 mL, 46.3 mmol) in DCE (100 mL) was allowed to stir at 70° C. for 1.5 h under nitrogen. MeOH (50 mL) was added and the mixture was stirred at the same temperature for 1 h. The mixture was cooled to rt and concentrated. The residue was triturated with MeOH (10 mL) and EtOAc (400 mL), and the white solid was collected on a funnel, washed with EtOAc (200 mL), and dried under reduced pressure to give 2-chloro-4-methyl-5,6,7,8-tetrahydro-1,6-naphthyridine hydrochloride (4.54 g): 1H NMR (400 MHz, DMSO-d6) δ ppm 9.54 (br s, 2 H), 7.33 (s, 1 H), 4.21-4.24 (app t, 2 H), 3.41-3.43 (m, 2 H), 3.05 (t, J=6.57 Hz, 2 H), 2.24 (s, 3 H); MS (ESI+) m/z 183.44 (M+H)+.
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