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Following the method of Bell et al. (J. Heterocyclic Chem. 1983, 20, 41), to a solution of 29.6 g (154 mmol) 2-amino-4,6-dichloro-pyrimidine-5-carbaldehyde in 31 acetic acid in a 2-necked flask at room temperature was added dropwise with stirring a solution of 11.8 g (170 mmol) hydroxylamine hydrochloride in 2.31 ethanol. Stirring was continued for 3 h at room temperature during which time crystallisation occurred. The crystals were collected by filtration to afford 26.8 g (84%) 2-amino-4,6-dichloro-pyrimidine-5-carbaldehyde oxime as a light yellow crystalline solid. ES-MS m/e (%): 209 ([M{37Cl, 37Cl}-H]−, 20), 207 ([M{37Cl, 35Cl}-H]−, 55), 205 ([M{35Cl, 35Cl}-H]−, 100).

1. customwas continued for 3 h at room temperature during which time crystallisation
2. filtrationThe crystals were collected by filtration