Preparation of 5-bromo-4-cyclopropylpyrimidine (11A): to a solution of 5-bromopyrimidine (3 g, 18.87 mmol) dissolved in ether (Et2O, 120 mL) and tetrahydrofuran (THF, 20 mL) was slowly added cyclopropylmagnesium bromide (39.6 mL, 19.81 mmol) at 0 °C. The reaction mixture was stirred at room temperature for 1 h. The reaction was quenched with water (0.340 mL, 18.87 mmol), followed by the addition of a THF (10 mL) solution of DDF (4.28 g, 18.87 mmol). The resulting black mixture was continued to stir overnight at room temperature. After completion of the reaction, the reaction mixture was extracted with ethyl acetate (EtOAc). The aqueous layer was again extracted with EtOAc and the organic layers were combined and washed sequentially with 1N NaOH solution and brine. The crude product was purified by BIOTAGE system (elution gradient: 0-15% EtOAc/hexane, elution volume 1.2 L) to afford the target compound 5-bromo-4-cyclopropylpyrimidine (700 mg, 20% yield) as a yellow solid. The product was characterized by 1H NMR (500 MHz, CDCl3): δ 8.87 (1H, s), 8.66 (1H, s), 2.40-2.56 (1H, m), 1.13-1.32 (4H, m).
