1. An aqueous solution (4 ml) of sodium nitrite (1.90 g, 27.5 mmol) was slowly added dropwise to an aqueous solution (20 ml) of sodium sulfate dihydrate (5.78 g, 25.0 mmol) under the condition of an ice bath and mixed with stirring.
2. The above mixed solution was prepared as solution A by dropping it into a beaker pre-filled with concentrated hydrochloric acid (5.1 ml) and ice (30 g) and continued to cool in an ice bath for 20 minutes.
3. In another vessel, sodium hydroxide (5.50 g, 138 mmol) and ice (20 g) were added to an aqueous solution (30 ml) of 3,5-dimethylphenol (3.05 g, 25.0 mmol) and stirred until completely dissolved.
4. Solution A was slowly added dropwise to the above 3,5-dimethylphenol solution under ice bath conditions, and after completion of the dropwise addition, stirring was continued in the ice bath for 1 hour.
5. The reaction mixture was heated to 65 °C to 75 °C and sodium lienodisulfate (16.8 g, 96.5 mmol) was added in batches until the solution was completely discolored.
6. After completion of the reaction, the solution was cooled to room temperature and stirring was continued for 30 minutes.
7. The reaction mixture was filtered and the solid product was collected and dried to give 4-amino-3,5-dimethylphenol (2.46 g, 72% yield).
