Example 1 Preparation of 2-chloro-5-nitropyrimidine: 5-nitropyrimidin-2-amine (0.98 g, 7 mmol, 1 eq.) was added to a solution of acetonitrile containing anhydrous copper(II) chloride (1.12 g, 8.4 mmol, 1.2 eq.), tert-butyl nitrite (1.24 mL, 10.5 mmol, 1.5 eq.), and MgSO4 (~300 mg) ( 40 mL) solution, and the reaction was stirred at 65-80 °C (bath temperature).After 30 min, the reaction mixture was cooled to room temperature and ether (100 mL) was added. The organic layer was separated and washed sequentially with aqueous 1N HCl (2 x 20 mL), H2O (50 mL) and brine (20 mL). The organic layer was dried over anhydrous Na2SO4 and concentrated under reduced pressure. The crude product was purified by column chromatography (eluent: hexane/ether=3:1) to afford the target product 2-chloro-5-nitropyrimidine as a light yellow solid (0.56 g, 50% yield).
