Zur Synthese sulfonierter Derivate von 4‐Fluoranilin

Syntheses of Sulfonated Derivatives of 4‐Fluoroaniline Synthesis of 2‐amino‐5‐fluorobenzenesulfonic acid ( 2 ) was achieved by baking the hydrogen sulfate of 4‐fluoroaniline ( 1 ). Sulfonation of p ‐fluoroacetanilide ( 4 ) with oleum followed by hydrolysis gave 5‐amino‐2‐fluorobenzenesulfonic acid ( 3 ). The same reaction with 1 yielded 3 in an impure state. The structures of 2 and 3 were confirmed by converting the diazonium chlorides derived from 5‐fluoro‐2‐nitroaniline ( 5 ) and from 2‐fluofo‐5‐nitroaniline ( 8 ) to 5‐fluoro‐2‐nitrobenzene‐sulfonyl chloride ( 6 ) and 2‐fluoro‐5‐nitrobenzenesulfonyl chloride ( 9 ), respectively, followed by hydrolysis of 6 to 5‐fluoro‐2‐nitrobenzenesulfonic acid ( 7 ), and of 9 to 2‐fluoro‐5‐nitrobenzenesulfonic acid ( 10 ), and by final reduction. Compound 10 was also obtained by sulfonation of 1‐fluoro‐4‐nitrobenzene ( 11 ) with oleum.