[CH3:1][SH:2].[H-].[Na+].[NH2:5][C:6]1[CH:15]=[CH:14][C:13]2[C:8](=[N:9][C:10](Cl)=[CH:11][CH:12]=2)[N:7]=1.O>CN(C)C=O.C(O)C>[NH2:5][C:6]1[CH:15]=[CH:14][C:13]2[C:8](=[N:9][C:10]([S:2][CH3:1])=[CH:11][CH:12]=2)[N:7]=1
To a solution, close to saturation, of methyl mercaptan in dimethylformamide (200 cc) maintained at 0° C., sodium hydride (13.3 g) in 50% strength suspension in mineral oil is added in small portions. 2-Amino-7-chloro-1,8-naphthyridine (25 g) is then added to this solution, and the mixture is heated at 100° C. for 2 hours. After being cooled, the reaction mixture is poured into water (500 cc) and extracted with methylene chloride (5×250 cc). The organic extracts are then washed with distilled water (2×200 cc), dried over magnesium sulphate and concentrated to dryness at 40° C. under reduced pressure (4 kPa). The product produced (22.9 g; m.p. 130° C.) is dissolved in boiling ethanol (150 cc). After 2 hours' cooling at 4° C., the crystallised solid is separated by filtration, washed with ethanol (10 cc) and then isopropyl ether (3×10 cc), and dried at 40° C. under reduced pressure (0.067 kPa). 2-Amino-7-methylthio-1,8-naphthyridine (9.6 g) is produced, m.p. 158° C.
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