The reaction of 2-chloro-4-fluorosulfonylbenzyl bromide (I) with triphenylphosphine (II) in refluxing benzene gives the corresponding triphenylphosphonium bromide (III), which is submitted to a Wittig condensation with 2-chloro-4-nitrocinnamaldehyde (IV) [prepared by an aldol condensation of 2-chloro-4-nitrobenzaldehyde (V) and acetaldehyde (VI)] yielding 1-(4-fluorosulfonyl-2-chlorophenyl)-4-(2-chloro-4-nitrophenyl)butadiene (VII). The reduction of (VII) with H2 over PtO2 in methoxyethanol affords 1-(4-fluorosulfonyl-2-chlorophenyl)-4-(2-chloro-4-aminophenyl)butane (VIII), which is finally cyclized with cyanoguanidine (IX) and acetone and treated with ethanesultonic acid.