4-[(tert-Butyldimethylsilyloxy)methyl]pyridine (II) was prepared by silylation of 4-hydroxymethylpyridine (I) with tert-butyldimethylsilyl chloride and imidazole. Deprotonation of (II) by means of LDA in cold THF, followed by condensation with 4-fluorobenzaldehyde (III), furnished the protected diol adduct (IV), which was further desilylated upon treatment with tetrabutylammonium fluoride in THF. Oxidation of the resultant diol (V) under Swern conditions provided diketone (VI). The triaryl imidazole (VIII) was then obtained by condensation of diketone (VI) with 4-(methylsulfanyl)benzaldehyde (VII) in the presence of ammonium acetate in refluxing HOAc. Finally, oxidation of the thioether function of (VIII) with K-2S2O8 furnished the title sulfoxide.
In a related procedure, 4-fluorobenzoyl chloride (IX) was converted to the corresponding Weinreb amide (X) upon treatment with N,O-dimethylhydroxylamine. Condensation of (X) with the lithium derivative of 4-[(tert-butyldimethylsilyloxy)methyl]pyridine (II) furnished the silylated hydroxy ketone (XI). This was then condensed with 4-(methylthio)benzaldehyde (VII) in the presence of cupric acetate as oxidant and ammonium acetate to produce the intermediate triaryl imidazole (VIII), which was finally oxidized as above.