10-Bromodecanenitrile (I) is prepared by starting from azelaic acid through the following steps: esterification, reduction of the ester groups to diols, then replacing the hydroxyl groups with dibromide by bromination, and finally displacing one bromo group with a cyano group. Compound (I) reacts with sodium methyl mercaptide to give 10-methylthiodecanenitrile (II), which is then treated with 29% hydrogen peroxide to yield 10-methylsulfonyldecanenitrile (III).