Reaction of 3,4-diaminopyridine (I) with potassium O-ethyl dithiocarbonate produced 2-mercaptoimidazo[4,5-c]pyridine (II), which was susequently alkylated with 3-methoxybenzyl bromide (III) and KOH, yielding sulfide (IV). Selective oxidation of (IV) to the target sulfoxide was then achieved by treatment with N-chlorosuccinimide in the presence of NaHCO3 at 0 C.