Synthesis
Step 5: 1-(4-hydroxyphenyl)propan-1-one (10.000 g, 66.587 mmol) and pyrrole hydrobromide were dissolved in acetic acid (25 ml) and the reaction mixture was stirred at room temperature for 3 hours and 5 minutes. Subsequently, water (110 ml) was added slowly and dropwise over a period of 20 min and stirring was continued for 30 min before adding water (40 ml). The reaction mixture was cooled to 0°C and allowed to stand at room temperature overnight. A solid precipitated from the reaction mixture and the solid product was collected by filtration, washed with water and dried under vacuum to afford 2-bromo-1-(4-hydroxyphenyl)propan-1-one as a white solid (13.76 g, 90% yield). The product was characterized by 1H-NMR (400 MHz, CDCl3): δ 7.96 (d, 2H), 6.91 (d, 2H), 5.25 (q, 1H), 1.87 (d, 3H). Mass spectrometry analysis showed m/z 229 (M + H)+.
Alternative method: 1-(4-hydroxyphenyl)propan-1-one (1 eq.) was dissolved in ethyl acetate (5 vol.) and a mixture of ground CuBr2 (2 eq.) in ethyl acetate (7.5 vol.) was added. The mixture was heated to reflux under vigorous stirring and kept at 60 °C for 4 hours of reaction. Upon completion of the reaction, it was filtered through a filtration aid and the residue was washed with ethyl acetate. The filtrate and washings were combined, treated with activated carbon, filtered again and the solvent evaporated to give the target product.
References
[1] Patent: WO2008/120000, 2008, A1. Location in patent: Page/Page column 34
[2] Patent: WO2015/48507, 2015, A1. Location in patent: Paragraph 0136
[3] Journal of the Chemical Society, 1954, p. 1034,1037
[4] Patent: US4690931, 1987, A
[5] Patent: WO2007/918, 2007, A1. Location in patent: Page/Page column 14-15
