59489-71-3

2032-35-1

912773-24-1

The general procedure for the synthesis of 2-bromoimidazo[1,2-a]pyrazines from 2-amino-5-bromopyrazines and bromoacetaldehyde diethyl acetal was as follows: a mixture of bromoacetaldehyde diethyl acetal (19.7 g, 0.1 mol) with 48% hydrobromic acid (4 mL) was heated to 140 °C under nitrogen protection and reacted for 1.5 hours. The reaction mixture was poured into a stirred suspension of sodium bicarbonate (40 g) with isopropanol (200 mL) and filtered after continued stirring for 10 minutes. To the filtrate was added 5-bromo-2-aminopyrazine (8.65 g, 0.05 mol) and the resulting solution was heated to reflux for 2 hours. After completion of the reaction, the solvent was removed by vacuum evaporation to give a dark brown viscous substance. The residue was washed with saturated sodium bicarbonate solution (150 mL) and extracted with dichloromethane (500 mL in two portions). The organic phases were combined, dried and vacuum evaporated to give a brown oil. The oily material was purified by fast chromatography using ethyl acetate as eluent to give 7.0 g of the target product 2-bromoimidazo[1,2-a]pyrazine as a light brown solid in 71% yield. The product was characterized by 1H-NMR (400 MHz, CDCl3): δ= 7.71 (s, 1H, Ar-H), 7.85 (s, 1H, Ar-H), 8.30 (s, 1H, Ar-H), 8.92 (s, 1H, Ar-H).