Synthesis
An aqueous solution of about 40% dimethylamine (35.68 kg, 1.0 eq.) was added to a 250 L reaction vessel under nitrogen protection and the mixture was cooled to about 4.5 °C. Glacial acetic acid (43.4 kg, 2.5 eq.) was slowly added dropwise over a period of 140 minutes while the reaction temperature was controlled to not exceed 15°C. After the dropwise addition was completed, stirring was continued for 20 minutes at about 3°C. Subsequently, 37% formaldehyde aqueous solution (25.9 kg, 1.1 eq.) was slowly added over about 20 minutes, keeping the reaction temperature between 0°C and 10°C. Upon addition of 6-fluoroindole (39.2 kg), the reaction was exothermic raising the temperature to about 40°C and subsequently cooled to about 20°C. The reaction solution was slowly transferred to a 650 L reactor filled with 3M NaOH aqueous solution, taking about 40 minutes. The resulting suspension was stirred at 5°C to 20°C for 40 minutes, the product was collected by filtration, washed with deionized water (120 kg) and dried at 50°C to afford 1-(6-fluoro-1H-indol-3-yl)-N,N-dimethylmethylamine (45.4 kg, 85% yield).
References
[1] Patent: US2011/152539, 2011, A1. Location in patent: Page/Page column 4
[2] Patent: US2016/168089, 2016, A1. Location in patent: Page/Page column 0081; 0082
[3] Chemical Communications, 2016, vol. 52, # 34, p. 5868 - 5871
[4] Journal of Organic Chemistry, 2018, vol. 83, # 17, p. 9902 - 9913
[5] Patent: WO2010/36362, 2010, A1. Location in patent: Page/Page column 44
