[CH3:1][O:2][C:3]1[C:14]([O:15][CH3:16])=[CH:13][C:6]2[S:7][C:8]([C:10]([NH2:12])=O)=[CH:9][C:5]=2[CH:4]=1.FC(F)(F)C(OC(=O)C(F)(F)F)=O>N1C=CC=CC=1.O>[CH3:1][O:2][C:3]1[C:14]([O:15][CH3:16])=[CH:13][C:6]2[S:7][C:8]([C:10]#[N:12])=[CH:9][C:5]=2[CH:4]=15,6-Dimethoxy-benzo[b]thiophene-2-carboxamide (65 g) was suspended in pyridine (325 ml). The solution was cooled to 0° C. and treated dropwise with trifluoro acetic anhydride (185 ml) whilst maintaining the internal reaction temperature below 10° C. The mixture was then stirred at room temperature for 30 min. then cooled and treated dropwise with water (170 ml) whilst maintaining the internal temperature below 30° C. The reaction mixture was diluted with more water (800 ml), stirred and the brown solid was filtered and dried under vacuum over calcium chloride at 60° C. Recrystallisation from acetone/ether afforded 5,6-dimethoxy-benzo[b]thiophene-2-carbonitrile as a white solid (47 g), m.p. 125° C.
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