[Br:1][C:2]1[CH:7]=[CH:6][C:5]([NH:8][C:9](=O)/[CH:10]=[CH:11]/[CH:12]2[CH2:17][CH2:16][O:15][CH2:14][CH2:13]2)=[C:4]([N+:19]([O-])=O)[CH:3]=1.C(O)(=O)C>CO.[Fe]>[Br:1][C:2]1[CH:7]=[CH:6][C:5]2[NH:8][C:9](/[CH:10]=[CH:11]/[CH:12]3[CH2:17][CH2:16][O:15][CH2:14][CH2:13]3)=[N:19][C:4]=2[CH:3]=1A solution of (E)-N-(4-bromo-2-nitro-phenyl)-3-(tetrahydro-pyran-4-yl)-acrylamide (1.26 g, 3.55 mmol, as prepared in the previous step) in 25 mL anhydrous MeOH was treated with glacial acetic acid (4 mL) and Fe powder (0.991 g, 0.0177 mol) and heated to 85° C. under a reflux condenser for 2 h. The resulting mixture was concentrated in vacuo, treated with saturated aqueous NaHCO3 (200 mL) and extracted thrice with 125 mL CH2Cl2. The combined organic layers were dried over MgSO4 and concentrated in vacuo. The residue was triturated with CH2Cl2, and the resulting solid was filtered and air-dried. The mother liquor was purified on an 80-g Sepra Si 50 SPE column (Isco system: flow rate=30 mL/min; eluting with EtOAc/hexane, 40:60 v/v over 10 min and 40:60 to 100:0, v/v over 30 min to yield (E)-5-bromo-2-[2-(tetrahydro-pyran-4-yl)-vinyl]-1H-benzimidazole as a white solid.
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