Synthesis
A 12 M hydrochloric acid solution (84.0 mL, 1.01 mol HCl) was slowly added dropwise to potassium permanganate (12.8 g, 81.0 mmol) over 40 min at 20 °C, with an increase in temperature during the reaction. The generated chlorine gas was absorbed at 0°C by stirring an aqueous solution (300 mL) of potassium hydroxide (50.5 g, 900 mmol). After the hydrochloric acid drop was completed, the residual chlorine gas was introduced into the aqueous solution by a stream of nitrogen gas for 45 min. Subsequently, 2,4,6-trimethoxybenzamide (48.7 g, 200 mmol) was added in a single addition at 0 °C. The reaction mixture was continued to be stirred at 0 °C for 6 h, followed by warming up to 20 °C for 12 h (the color of the reaction solution changed from colorless to dark brown). After that, sodium sulfite (12.7 g, 101 mmol) was added at once at 20 °C and stirring was continued for 15 min. After completion of the reaction, the precipitate was separated by filtration and the filter cake was washed sequentially with water (100 mL) and ether (200 mL). The filtrate and washings were combined and the organic layer was separated by sufficient shaking. The aqueous phase was extracted with ether (2 x 200 mL). All organic phases were combined, dried with anhydrous sodium sulfate, and concentrated under reduced pressure (rotary evaporator, 800 mbar, 40 °C) to remove solvent. The dark brown residue was purified by ball-ball distillation (Kugelrohr apparatus, 110-140 °C/0.1 mbar) to afford 2,4,6-trimethoxyaniline as a colorless liquid (13.9 g, 75.9 mmol) in 38% yield. The product crystallized at 4 °C with a melting point of 29-31 °C. Elemental analysis (C9H13NO3) Calculated values: C, 59.00; H, 7.15; N, 7.65. Measured values: C, 58.9; H, 7.1; N, 7.5.
References
[1] Patent: WO2004/45625, 2004, A1. Location in patent: Page/Page column 16,17
[2] ChemMedChem, 2011, vol. 6, # 11, p. 2070 - 2080
[3] Patent: WO2004/45625, 2004, A1. Location in patent: Page/Page column 15,16
