3-BROMOIMIDAZO[1,2-A]PYRAZINE

Synthesis

The general procedure for the synthesis of 3-bromoimidazo[1,2-A]pyrazines from indolo[1,2-A]pyrazines was as follows: imidazo[1,2-α]pyrazines (90 mg, 0.76 mmol) and sodium acetate (75 mg, 0.91 mmol) were dissolved in methanol (2 mL) saturated with potassium bromide and the mixture was cooled to -10 °C. Subsequently, bromine (121 mg, 0.76 mmol) was slowly added dropwise over 5 min. After the dropwise addition was completed, 1N sodium sulfite solution (2 mL) was added to terminate the reaction, followed by removal of the solvent under vacuum. The residue was dissolved in a mixture of water (15 mL) and saturated sodium bicarbonate solution (15 mL) and extracted with ethyl acetate (2 x 40 mL). The organic phases were combined, washed with brine (40 mL), dried over anhydrous sodium sulfate and the solvent evaporated to give 3-bromoimidazo[1,2-α]pyrazine (150 mg, 100% yield) as a white crystalline solid. The NMR hydrogen spectrum (400 MHz, CDCl3) data were as follows: δH 7.80 (1H, s), 6.87 (1H, d, J=7 Hz), 7.71 (1H, s), 8.27 (1H, d, J=7 Hz).

References

[1] Patent: US2004/19057, 2004, A1. Location in patent: Page/Page column 9
[2] Tetrahedron, 2011, vol. 67, # 47, p. 9063 - 9066
[3] Patent: WO2010/125101, 2010, A1. Location in patent: Page/Page column 50
[4] Patent: CN104341425, 2018, B. Location in patent: Paragraph 0169; 0171; 0174; 0175