5-Nitrofurfural → 5-(5,6-difluoro-1H-benzimidazol-2-ylsulfanyl)-furan-2-carbaldehyde

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Reaction Steps

5,6-Difluoro-1,3-dihydro-benzimidazole-2-thione (1.0 g, 5.37 mmol) is suspended into 50 mL of tetrahydrofuran under argon. Then, 0.39 g (8.06 mmol) of sodium hydride is added. The reaction mixture is stirred at room temperature until gas evolution has ceased. 5-Nitro-2-furaldehyde (0.76 g, 5.37 mmol) is then added and the reaction mixture is stirred at room temperature for 16 h, upon which it is poured on ice and extracted 3 times with ethyl acetate. The organic extracts are combined, washed with brine, dried on magnesium sulfate, filtered and concentrated under reduced pressure. The residue is purified by chromatography on a prepacked 200 g 15-40 μm silica gel cartridge (eluting solvent: dichloromethane/methanol 95/5 v/v; rate: 40 mL/min). The fractions containing the desired product are combined and concentrated to dryness under reduced pressure. The residue is recrystallized from ethyl acetate/n-heptane, filtered, washed with n-heptane and dried under reduced pressure. 1.16 g of 5-(5,6-difluoro-1H-benzimidazol-2-ylsulfanyl)-furan-2-carbaldehyde is obtained as a crystalline brown powder. mp: 133° C.

Provenance & Evidence