合成路线1

The acetylation of 2,3,5-trimethyl-4-nitropyridine N-oxide (I) with acetic anhydride in hot acetic acid gives the 2-(acetoxymethyl)-3,5-dimethyl-4-nitropyridine (II), which, without isolation, is treated with NaOH in hot dichloromethane/water, yielding the corresponding 2-(hydroxymethyl) derivative (III). This compound, also without isolation, is treated with SOCl2 to afford 2-(chloromethyl)-3,5-dimethyl-4-nitropyridine (IV), which is condensed with 6-methoxy-1H-benzimidazole-2-thiol (V) by means of tetrabutylammonium bromide and NaOH in dichloromethane/water, providing the corresponding thioether (VI). The reaction of (VI) with sodium methoxide and K2CO3 in refluxing methanol yields 5-methoxy-2-(4-methoxy-3,5-dimethylpyridin-2-ylmethylsulfanyl)-1H-benzimidazole (VII), which is finally oxidized to the target sulfoxide with peracetic acid (VIII) in ethyl acetate.