ETHYL IMIDAZO[1,2-A]PYRAZINE-2-CARBOXYLATE

5049-61-6

70-23-5

77112-52-8

Method A-Oxide To a stirred dimethoxyethane solution of 2-aminopyrazine (1.0 g, 10.5 mmol) was added dropwise ethyl 3-bromopyruvate (2.36 g, 13.0 mmol) at room temperature and the reaction mixture was continued to stir for 2.5 hours at room temperature. Subsequently, the reaction mixture was cooled to 0 °C and maintained at this temperature with stirring for 30 min, during which a light brown precipitate was generated. The precipitate was collected by filtration and washed with ethyl acetate to give a light brown solid. The solid was suspended in 50 mL of ethanol and heated to reflux temperature until a clarified solution was formed. After refluxing the reaction for 2 hours, the reaction mixture was concentrated under reduced pressure. The concentrate was subsequently treated with a mixture of CH2Cl2 and saturated aqueous NaHCO3. The mixture was filtered through a diatomaceous earth pad, the organic layer was separated and dried with anhydrous Na2SO4 and filtered to remove the desiccant. The filtrate was concentrated under reduced pressure and the residue was purified by silica gel column chromatography with CH2Cl2:MeOH (99:1 to 97:3, v/v) as eluent. The target fraction was collected and concentrated under reduced pressure to afford ethyl imidazo[1,2-a]pyrazine-2-carboxylate as light yellow crystals (0.546 g, 27% yield).1H NMR (400 MHz, CDCl3) δ 9.21 (s, 1H), 8.26 (s, 1H), 8.09 (dd, J = 4.7,1.6 Hz, 1H), 7.96 (d, J = 4.7 Hz, 1H), 4.49 (q, J=7.1 Hz, 2H), 1.45 (t, J=7.1 Hz, 3H).