Zur Synthese sulfonierter Derivate von 2,3-Dimethylanilin und 3,4-Dimethylanilin

Article abstract of DOI:10.1002/hlca.19800630208

Baking the hydrogensulfate salt of 2,3-dimethylaniline (1) or of 3,4-dimethylaniline (2) led to 4-amino-2,3-dimethylbenzenesulfonic acid (4) and 2-amino-4,5-dimethylbenzenesulfonic acid (5), respectively (Scheme 1).The sulfonic acid 5 was also obtained by treatment of 2 with sulfuric acid or by reaction of 2 with amido-sulfuric acid. 3-Amino-4,5-dimethylbenzenesulfonic acid (3) and 5-amino-2,3-dimethylbenzenesulfonic acid (6) were prepared by sulfonation of 1,2-dimethyl-3-nitrobenzene (9) to 3,4-dimethyl-5-nitrobenzenesulfonic acid (11) and of 1,2-dimethyl-4-nitrobenzene (10) to 2,3-dimethyl-5-nitrobenzenesulfonic acid (12), respectively, with subsequent Bechamp reduction (Scheme 1).Preparations of 2-amino-3,4-dimethylbenzenesulfonic acid (7) and of 6-amino-2,3-dimethylbenzenesulfonic acid (8) were achieved by the sulfur dioxide treatment of the diazonium chlorides derived from 3,4-dimethyl-2-nitroaniline (24) and from 2,3-dimethyl-6-nitroaniline (31) to 3,4-dimethyl-2-nitrobenzenesulfonyl chloride (29) and 2,3-dimethyl-6-nitrobenzenesulfonyl chloride (32), respectively, followed by hydrolysis to 3,4-dimethyl-2-nitrobenzenesulfonic acid (30) and 2,3-dimethyl-6-nitrobenzenesulfonic acid (33), and final reduction (Scheme 3).Compound 7 was also synthesized by reaction of 4-chloro-2,3-dimethylaniline (23) with amidosulfuric acid to 2-amino-5-chloro-3,4-dimethylbenzenesulfonic acid (20) and subsequent hydrogenolysis (Scheme 2). 4'-Bromo-2',3'-dimethyl-acetanilide (13) and 4'-chloro-2',3'-dimethyl-acetanilide (14) on treatment with oleum yielded 5-acetylamino-2-bromo-3,4-dimethylbenzenesulfonic acid (17) and 5-acetylamino-2-chloro-3,4-dimethylbenzenesulfonic acid (18), respectively.Their structures were proven by hydrolysis to 5-amino-2-bromo-3,4-dimethylbenzenesulfonic acid (21) and 5-amino-2-chloro-3,4-dimethylbenzenesulfonic acid (22), followed by reductive dehalogenation to 3.Reaction of 1 with sulfuric acid gave a mixture of 3,4 and 7, whereas sulfonation of 2',3'-dimethyl-acetanilide with subsequent hydrolysis led to a mixture of 3 and 4.Treatment of 3',4'-dimethyl-acetanilide with oleum followed by hydrolysis resulted in the formation of mainly 5 and a small amount of unknown product.