Reaction of methanesulfonamide derivative (I) with 4-iodo-N,N-dimethyl-1H-imidazole-1-sulfonamide (I) and EtMgBr in CH2Cl2 followed by heating with diluted HCl affords compound (III), which is debenzylated and reduced by hydrogenation over Pd/C in MeOH.

Treatment of 4-iodo-N,N-dimethyl-1H-imidazole-1-sulfonamide (I) with EtMgBr and 3-nitrobenzaldehyde (II) in CH2Cl2 yields derivative (III), whose nitro moiety is reduced by hydrogenation over Pd/C in EtOAc to afford aminophenyl derivative (IV). Treatment of (IV) with Et3SiH in TFA provides aminobenzyl derivative (V), which is finally converted into the desired compound by treatment with pyridine and ethanesulfonyl chloride (VI) followed by reflux in HCl.