The acetylation of 1,2,3,4-tetrahydroisoquinoline (I) with acetic anhydride gives 2-acetyl-1,2,3,4-tetrahydroisoquinoline (II), which is sulfonated with chloro sulfonic acid in methylene chloride yielding 2-acetyl-7-chlorosulfonyl-1,2,3,4-tetrahydroisoquinoline (III). The reaction of (III) with 3-chloroaniline (IV) and triethylamine in refluxing acetone affords 2-acetyl-7-(3-chlorophenylamino sulfonyl)-1,2,3,4-tetrahydroisoquinoline (V), which is deacetylated by a treatment with HCl in refluxing butanol to 7-(3-chlorophenylaminosulfonyl)-1,2,3,4-tetrahydroisoquinoline (VI). Finally, this compound is condensed with bis(chlorosulfonyl)imide (VII) [prepared with chlorosulfonic acid (VIII) and chlorosulfonyl isocyanate (IX)] in acetonitrile containing triethylamine.