Synthesis
General procedure for the synthesis of the compound (CAS:4425-93-8) from formaldehyde and fluorene: Dimethyl sulfoxide (DMSO) (300 mL), toluene (300 mL), and paraformaldehyde (PF) (40 g) were added to a round-bottomed flask, mixed, and then cooled to 13-15 °C. Subsequently, 30% sodium methanol solution (26 g) was slowly added to the mixture. Fluorene (100 g, 0.6 mol) in powder form was added to the reaction mixture in batches over a period of 15 min while controlling the temperature at 14-16 °C. It was observed that paraformaldehyde dissolved rapidly upon addition of fluorene. The reaction mixture was continued to be stirred at 14-16 °C for 30 min to obtain a clarified light yellow solution. Subsequently, the reaction solution was adjusted to neutral (pH 6-7) by slowly adding concentrated hydrochloric acid (8-10 mL) to terminate the reaction. Water (1000 mL) was gradually added to the reaction solution and the mixture was cooled to 10 °C and maintained for 3 hours. The solid product was collected by filtration and washed with cold toluene (twice, 25 mL each). The solid product was placed under vacuum until the toluene completely evaporated. The wet weight was 120 g. Subsequently, the product was dried to constant weight at 60-70 °C to a dry weight of 90-95 g in 70% yield. The product was analyzed by HPLC and showed a purity of >98% with a melting point of 139-144°C.
References
[1] Patent: WO2018/42013, 2018, A1. Location in patent: Page/Page column 17; 18
[2] Patent: WO2016/193215, 2016, A1. Location in patent: Page/Page column 18; 19
[3] Patent: WO2016/193212, 2016, A1. Location in patent: Page/Page column 17-18
[4] Journal of the American Chemical Society, 1959, vol. 81, p. 1172,1175
[5] Journal of the American Chemical Society, 1960, vol. 82, p. 4945 - 4952
