N-(2-Methoxyphenyl)piperazine (I) is protected as the trichloroacetamide (II) using trichloroacetyl chloride and diisopropylethylamine. Then, chlorosulfonation of (II) in cold CH2Cl2 furnishes sulfonyl chloride (III)

Alkylation of 2,4-dichloro-6-nitrophenol (IV) with iodomethane in the presence of K2CO3 provides the methyl ether (V). Subsequent nitro group reduction in (V) employing iron powder and NH4Cl leads to aniline (VI). This is then acylated by sulfonyl chloride (III) to form sulfonamide (VII). The N-trichloroacetyl group of (VII) is finally removed by alkaline hydrolysis to provide the title compound