Bemerkungen zur Synthese von 3-Aminotoluol-5-sulfonsäure und 2-Aminotoluol-3-sulfonsäure

✍ Scribed by Alfred Courtin

• Book ID: 102856497
• Publisher: John Wiley and Sons
• Year: 1976
• Tongue: German
• Weight: 605 KB
• Volume: 59
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19760590206

✦ Synopsis

Some comments on the synthesis of 3‐aminotoluene‐5‐sulfonic acid and 2‐aminotoluene‐3‐sulfonic acid.

Sulfonation of 3‐nitrotoluene (5) yields predominantly the unsymetrical isomer 5‐nitrotoluene‐2‐sulfonic acid (7), and lesser amounts of 5‐nitrotoluene‐3‐sulfonic acid (6), previously reported as the major product. The desired 5‐aminotoluene‐3‐sulfonic acid (3) was synthesized in preparative amounts from 6‐aminotoluene‐3‐sulfonic acid (4) via the following sequence of reactions: diazotation and Sandmeyer replacement of 6‐chlorotoluene‐3‐sulfonic acid (13), nitration of the sulfonyl chloride 14 under suitable conditions to give isomer free 6‐chloro‐5‐nitrotoluene‐3‐sulfonyl chloride (15), hydrolysis to the sulfonic acid 16 and finally, simultaneous hydrogenolysis and reduction to 3. The isomeric 7 was unequivocally prepared from 2‐amino‐5‐nitrotoluene (9) via two routes: (1) diazotation, Sandmeyer thiocyanatation to 5‐nitro‐2‐thiocyanatotoluene (10), Na~2~S reduction to the di(2‐methyl‐4‐nitro‐phenyl)‐disulfide (11), treatment with nitric acid and chlorine to give 5‐nitrotoluene‐2‐sulfonyl chloride (12) and finally alkaline hydrolysis to 7; (2) Meerwein's SO~2~ treatment of the diazonium salt derived from 9 leads directly to 12 and thence to 7.

2‐Aminotoluene‐3‐sulfonic acid (1) was prepared from the key intermediate 3‐amino‐2‐nitrotoluene (18) via the same two routes used to prepare 7 from 9. Both reaction sequences provided 2‐nitrotoluene‐3‐sulfonly chloride, the hydrolysis product of which was reduced to 1. Intermediate 18 was prepared in the following four steps from m‐toluic acid (19): nitration to the 2‐nitroderivative (20), whose acid chloride (21) was converted to 2‐nitro‐m‐toluamide (22), and Hoffmann rearrangement to 18.