General procedure for the synthesis of ethyl 4-chloro-2-methylpyrimidine-5-carboxylate from ethyl 2-methyl-4-hydroxypyrimidine-5-carboxylate: Phosphoryl chloride (50 mL, 23.33 mmol) was slowly added to ethyl 2-methyl-6-oxo-1,6-dihydropyrimidine-5-carboxylate (Intermediate 174, 4.25 g, 23.33 mmol). The resulting insoluble mixture was heated to reflux for 30 min. During the reaction, the product gradually dissolved in phosphoryl chloride while the feedstock remained insoluble. Upon completion of the reaction, the excess phosphoryl chloride was evaporated under reduced pressure. The residue was evaporated to dryness, redissolved in ethyl acetate (100 mL) and washed sequentially with water (75 mL) and saturated saline (75 mL). The organic layer was dried over anhydrous magnesium sulfate, filtered and concentrated to give the crude product. The crude product was purified by fast silica gel column chromatography with an eluent of 10% to 30% ethyl acetate/isohexane gradient. The purified grades were collected and concentrated to dryness to afford ethyl 4-chloro-2-methylpyrimidine-5-carboxylate (2.70 g, 57.7% yield) as a colorless oil.1H NMR (400.132 MHz, CDCl3) δ 1.42 (3H, t), 2.78 (3H, s), 4.44 (2H, q), 9.05 (1H, s). Mass spectrum (ESI+) m/z (M + H)+ = 201; HPLC retention time tR = 2.17 min.
