Sodium hydride → 1-(3,7-dimethyl-2,6(E)-octadienyl)-6-methoxy-1H-1,3-benzimidazole

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Reaction Steps

To a suspension of sodium hydride (0.25 g, 11 mmol) in dimethylformamide (10 mL) at 0° C. under nitrogen was added 6-methoxy-2-mercaptobenzimidazole (1.98 g, 11 mmol) in dimethylformamide (20 mL). The solution was allowed to stir to ambient temperature, then geranyl chloride (1.9 g, 11 mmol) was added and the reaction mixture stirred at 90° C. overnight. Evaporation of the solvent gave a residue which was dissolved in CH2Cl2, washed with H2O and dried over Na2SO4. Evaporation and flash chromatography (Merck Kieselgel, 5% MeOH/CH2Cl2) gave 1-(3,7-dimethyl-2,6(E)-octadienyl)-6-methoxy-1H-1,3-benzimidazole (free base) (2.4 g, 77%) as a 1:1 mixture of 5- and 6-methoxy isomers. Conversion to the oxalate salt in diethyl ether filtration 10 minutes after addition of oxalic acid gave 500 mg of the title compound as a white solid (pure 6-methoxy by 400 MHz NMR with NOE). m.p. 90°-94° C. NMR (DMSO-d6)δ8.3(s,1H), 7.68(d,J=2 Hz,1H), 7.63(d,J=9 Hz,1H), 7.23(m,1H), 5.3 d,J=7 Hz, 1H), 5.0(m,1H), 4.90(d,J=8 Hz,2H), 2.0(m,4H), 1.70(s,3H), 1.58(s,3H), 1.55(s,3H).

Provenance & Evidence