5-Bromo-benzo[2,1,3]thiadiazole → 5-Cyano-2,1,3-benzothiadiazole
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Br[C:2]1[CH:3]=[CH:4][C:5]2[C:6]([CH:10]=1)=[N:7][S:8][N:9]=2.[C:11]([Cu])#[N:12]>CN(C=O)C.Cl.O>[C:11]([C:2]1[CH:3]=[CH:4][C:5]2=[N:9][S:8][N:7]=[C:6]2[CH:10]=1)#[N:12]Br[C:2]1[CH:3]=[CH:4][C:5]2[C:6]([CH:10]=1)=[N:7][S:8][N:9]=2.[C:11]([Cu])#[N:12]>CN(C=O)C.Cl.O>[C:11]([C:2]1[CH:3]=[CH:4][C:5]2=[N:9][S:8][N:7]=[C:6]2[CH:10]=1)#[N:12]5-Bromobenzo[1,2,5]thiadiazole from Step 1 was dissolved in anhydrous DMF (160 mL) under nitrogen. Then, CuCN (7.27 g, 81 mmol) was added and the mixture was heated to 150° C. overnight. After cooling down, a solution of FeCl3 (19.7 g) in concentrated HCl (7 mL) and water (40 mL) was added dropwise and the mixture was stirred at 70° C. for minutes. After extraction with DCM (200 ml×2), the combined organic phases were extracted with HCl (6M, 100 mL×3), water (100 mL), and brine (100 mL), and dried over MgSO4. Concentration gave a brown solid which was purified by column chromatography with DCM as the eluent. Finally, a white solid was obtained (2.95 g, 65% yield for two steps). 1H NMR (CDCl3 500 MHz): δ: 8.48 (d, 1H, J=1.5 Hz), 8.16 (d, 1H, J=9.0 Hz), 7.75 (dd, 1H, J=9.0, 1.5 Hz).
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