Nitration of 1-(2-methoxyphenyl)piperazine (I) using KNO3 in H2SO4 gave (II). After protection of (II) as the N-Boc derivative (III), reduction of the nitro group by catalytic hydrogenation over Pd/C yielded aniline (IV). This was condensed with 5-chloro-3-methylbenzothiophene-2-sulfonyl chloride (V) to afford the corresponding sulfonamide (VI). Finally, the Boc protecting group of (VI) was removed with HCl in boiling THF.
The title sulfonamide was prepared by coupling 4-methoxy-3-(4-methylpiperazin-1-yl)aniline (II) with 4-iodobenzenesulfonyl chloride (I) in acetone.