[Na].[N:2]1[CH:7]=[CH:6][CH:5]=[C:4]([C@@H:8]2[CH2:13][CH2:12][CH2:11][CH2:10][S@:9]2=[O:14])[CH:3]=1.[CH3:15][N:16]=[C:17]=[S:18].[Cl-].[NH4+]>O1CCCC1.[N+]([O-])([O-])=O.[Fe+3].[N+]([O-])([O-])=O.[N+]([O-])([O-])=O.CO>[N:2]1[CH:7]=[CH:6][CH:5]=[C:4]([C@@:8]2([C:17](=[S:18])[NH:16][CH3:15])[CH2:13][CH2:12][CH2:11][CH2:10][S@:9]2=[O:14])[CH:3]=1
Ammonia gas is condensed at -50° C. to obtain 2 ml of liquid ammonia, which is treated with iron (III) nitrate (0.0015 g), followed by sodium metal (0.02 g). The solution turns blue and then dark grey after 20 minutes. It is then treated with a solution of (1R,2S)-2-(3-pyridyl)tetrahydro-2H-thiopyran 1-oxide (0.06 g) in tetrahydrofuran (8 ml) during 2 minutes, at -40° C. The mixture is stirred for 2 minutes and is then treated with a solution of methyl isothiocyanate (0.033 g) in tetrahydrofuran (2 ml), by syringe. The reaction mixture is stirred for 5 minutes at -35° C. and then treated with ammonium chloride (0.05 g) and warmed to 20° C. The mixture is treated with methanol (0.3 ml) and evaporated under reduced pressure. The residue is partitioned between brine (10 ml) and dichloromethane (3×30 ml). The organic phases are combined and dried with magnesium sulphate, filtered and evaporated under reduced pressure, to give (1R,2R)-2-(3-pyridyl)-N-methyltetrahydro-2H-thiopyran-2-carbothioamide 1-oxide (0.4 g; 99% ee) in the form of a white solid, m.p. 215° C. [NMR (CDCl3): 8.7(s,1H); 8.5(s,2H); 8.1(d,1H); 7.3(s,1H); 3.8(s,1H); 3.1(d,3H); 2.8(s,1H); 2.4-1.5(m,6H)].
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