Sematilide is an antiarrhythmic agent. It is the same structure as for procainamide, differing only by the placement of a mesyl sulfonamide moiety to the anilino nitrogen.
The reaction between Benzocaine (Ethyl 4-Aminobenzoate) [94-09-7] (1) and mesyl chloride [124-63-0] gives the sulfonamide, Ethyl 4-(Methylsulfonamido)benzoate [7151-77-1]. Base saponification followed by the removal of the water from the reaction mixture gives 4-[(Methylsulfonyl)amino]benzoic acid sodium salt (2). Halogenation with thionyl chloride gives 4-[(Methylsulfonyl)Amino]Benzoyl Chloride [63421-72-7]. Amide formation with N,N-Diethylethylenediamine [100-36-7] (3) then concludes the synthesis of Sematilide (4).