Synthesis
The general steps for the synthesis of 2-amino-3-iodo-5-bromopyridine from 2-amino-5-bromopyridine are as follows:
Step 1: Iodination reaction
5-Bromo-pyridin-2-ylamine (50 g, 289 mmol) was dissolved in 2 M sulfuric acid (500 mL) and potassium iodate (30.8 g, 144 mmol) was added in batches. The mixture was heated to 100°C and an aqueous solution of potassium iodide (26.5 g, 160 mmol) was added slowly and dropwise (50 mL) over about 1 hour. After 1 hour of reaction, stirring was continued for 30 minutes, followed by cooling to room temperature. The pH of the aqueous phase was adjusted to 8-9 with alkali and then the mixture was extracted with ethyl acetate (3 times). The organic layers were combined and washed sequentially with aqueous sodium thiosulfate, water and brine, dried (Na2SO4) and concentrated to give 2-amino-3-iodo-5-bromopyridine as a brown solid (77.4 g, 90% yield).
NMR data (300 MHz, CDCl3): δ 8.06 (d, J = 2.2 Hz, 1H), 7.96 (d, J = 2.2 Hz, 1H), 4.96 (s, 2H).
References
[1] Angewandte Chemie - International Edition, 2013, vol. 52, # 38, p. 10093 - 10096
[2] Angew. Chem., 2013, vol. 52, # 38, p. 10093 - 10096,4
[3] Patent: WO2011/73263, 2011, A1. Location in patent: Page/Page column 78
[4] Patent: WO2012/10538, 2012, A2. Location in patent: Page/Page column 28
[5] Patent: US2012/22258, 2012, A1. Location in patent: Page/Page column 13-14
