N-chlorosuccinimide (2.67 g, 20 mmol) and pyridine (0.1 mL) were dissolved in chloroform (18 mL) at 5 °C, followed by the addition of glyoxime (1.18 g, 20 mmol) in batches. After the addition was completed, the reaction mixture was stirred at room temperature for 10 min, after which methyl propargylate (2.22 mL, 25 mmol) was added. Next, a chloroform (3 mL) solution of triethylamine (2.92 mL, 21 mmol) was added dropwise at a controlled rate of 15-18 °C. Upon completion of the dropwise addition, the reaction mixture was continued to be stirred at 18 °C for 20 min, followed by the addition of water (15 mL) for quenching. The organic layer was separated and washed with 15 mL of water and subsequently dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The residue was treated with ether (20 mL) and the resulting precipitate was collected by filtration and dried to give methyl 3-methylisoxazole-5-carboxylate (1.75 g, 12.4 mmol, 62% yield) as a brown solid, which was used directly in the next step of the reaction. The product was characterized by 1H-NMR (CDCl3, Bruker 400MHz): δ 2.38 (3H, s); 3.96 (3H, s); 6.80 (1H, s).
