合成路线1

The chlorination of 2,3-dimethyl-4-(2,2,2-trifluoroethoxy)pyridine-N-oxide (I) with trichloroisocyanuric acid in hot chloroform gives the 2-chloromethyl derivative (II), which is condensed with 2-mercapto-1H-benzimidazole (III) by means of NaOH in methanol to yield the adduct (IV). The reaction of (IV) with PCl3 and acetic acid eliminates the N-oxide group, affording the sulfanylmethylpyridine (V). Finally, this compound is oxidized with tert-butyl hydroperoxide (VI) in ethanol to provide the target sulfoxide. Alternatively, the intermediate adduct (IV) can also be obtained as follows: The chlorination of 2,3-dimethyl-4-nitropyridine-N-oxide (VII) with trichloroisocyanuric acid as before gives the chloromethyl derivative (VIII), which is condensed with 2-mercapto-1H-benzimidazole (III) as before to yield the adduct (IX). Finally, this compound is treated with 2,2,2-trifluoroethanol (X), benzyltrimethylammonium chloride and K2CO3 in acetonitrile to afford the target intermediate (IV).