[N:1]1[CH:6]=[CH:5][CH:4]=[CH:3][C:2]=1[C:7]([NH2:9])=O.C(O[CH:15]([N:19]([CH3:21])C)[N:16](C)C)(C)(C)C.[O-]CC.[Na+].C(O)C.NC(N)=[S:31]>CN(C)C=O>[N:1]1[CH:6]=[CH:5][CH:4]=[CH:3][C:2]=1[C:7]1[N:9]=[CH:21][N:19]=[C:15]([SH:31])[N:16]=1
To a stirred solution of picolamide (1.50 g, 12.3 mmol) in N,N-dimethylformamide (20 mL) was added tert-butoxybis(dimethylamino)methane (5.2 mL, 25 mmol). The mixture was refluxed for 2.5 hours and then concentrated. The resulting viscous brown oil was taken up in a 0.5 M solution of sodium ethoxide in ethanol (50 mL, 25 mmol). Thiourea (0.72 g, 9.5 mmol) was added and the solution was refluxed for 2.5 hours. The reaction was concentrated and the residue partitioned between ethyl acetate and dilute aqueous sodium hydroxide solution. The aqueous layer was washed twice with ethyl acetate and neutralized with 1 N aqueous hydrochloric acid. The resulting precipitate was filtered off and rinsed with water. Vacuum oven dying afforded 0.72 g (40%) of crude product as a fine brown solid. This material was used without further purification in the next step.
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