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1) Oxalyl chloride (12 ml, 137 mmol) was added slowly and dropwise to a solution of chlorobenzene (50 ml) in 2-methylaminoacetonitrile hydrochloride (6.4 g, 39.9 mmol) at room temperature. Subsequently, the reaction mixture was slowly heated to 90 °C and the reaction was stirred at this temperature overnight. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure and the resulting residue was purified by silica gel column chromatography (eluent: petroleum ether/ethyl acetate = 10:1) to afford 3,5-dichloro-1-methylpyrazin-2(1H)-one as a yellow oil (5 g, 70% yield). lC-MS (ESI+): m/z 178 ([M+H]+), retention time (Rt): 1.54 min.

[1] Patent: WO2014/140184, 2014, A1. Location in patent: Page/Page column 75
[2] Patent: US2013/40928, 2013, A1. Location in patent: Paragraph 0245; 0246; 0247
[3] Journal of Heterocyclic Chemistry, 1983, vol. 20, # 4, p. 919 - 923
[4] Patent: US2010/298334, 2010, A1. Location in patent: Page/Page column 56