Synthesis
The general procedure for the synthesis of 2,4-dibromoiodobenzene from 2,4-dibromoaniline is as follows:[Example of Manufacture 1]; Intermediate A1 of indeno compound A was produced by the following synthetic route.2,4-Dibromoaniline (10 g, 40 mmol) was suspended in an aqueous hydrochloric acid solution comprising 40 mL of concentrated hydrochloric acid and 30 mL of water, and the suspension was cooled at -8°C in an ice/salt bath. Aqueous sodium nitrite (3.0 g, 43 mmol, 1.1 eq./15 mL) was added dropwise over a period of 10 min, followed by stirring of the reaction mixture at -10 °C to 0 °C for 30 min to prepare the diazonium salt. The reaction solution was slowly added dropwise to an aqueous potassium iodide solution (60 g, 0.36 mmol, 9 eq/180 mL) over 20 min at room temperature. The reaction mixture was continued to be stirred at room temperature for 3 hours, after which dichloromethane (200 mL) and sodium bisulfite (2 g) were added to neutralize the free iodine. The organic layer was separated and washed sequentially with aqueous sodium bisulfite (100 mL) and saturated brine (30 mL) before drying with anhydrous magnesium sulfate. Subsequently, the solvent was removed by distillation to give a red liquid product. The product was purified by column chromatography (silica gel/hexane) to give a white solid (11.0 g, 76% yield).1H-NMR (400 MHz, CDCl3, TMS) data were as follows: δ 7.11 (1H, dd, J=8Hz, 2Hz), 7.69 (1H, d, J=8Hz), 7.76 (1H, d, J=2Hz).
References
[1] Organometallics, 2015, vol. 34, # 20, p. 4798 - 4801
[2] Angewandte Chemie - International Edition, 2008, vol. 47, # 5, p. 888 - 890
[3] Patent: EP2316816, 2011, A1. Location in patent: Page/Page column 14
[4] Journal of Organic Chemistry, 1987, vol. 52, # 5, p. 748 - 753
[5] Inorganic Chemistry, 2012, vol. 51, # 2, p. 799 - 811
