[Cl:1][C:2]1[CH:7]=[CH:6][C:5]([NH:8][CH2:9][CH2:10][CH2:11][NH:12][CH2:13][CH3:14])=[C:4]([CH3:15])[CH:3]=1.[C:16](N1C=CN=C1)(N1C=CN=C1)=[S:17].O.C1(C)C=CC(S(O)(=O)=O)=CC=1>O1CCOCC1>[Cl:1][C:2]1[CH:7]=[CH:6][C:5]([N:8]2[CH2:9][CH2:10][CH2:11][N:12]([CH2:13][CH3:14])[C:16]2=[S:17])=[C:4]([CH3:15])[CH:3]=1The cyclization of the crude diamine of Step D was carried out with one equivalent of 1,1′-thiocarbonyldiimidazole in refluxing dioxane under nitrogen for one hour. Subsequently, two equivalents of para-toluenesulfonic acid hydrate were added and the mixture was refluxed for 48 hours. The solvent was removed in vacuo and the residue was dissolved in dichloromethane (100 mL). The solution was washed with water, dried over magnesium sulfate, filtered and evaporated. The crude product was purified by flash chromatography (on Merck-60 silica gel) eluting with 10-25% petroleum ether/ethyl acetate. The title compound was obtained as a white solid (4.4 g, 52%), m.p. 116-118° C.
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