Tetrahydropyran-4-carboxylic acid (1.00 g, 7.68 mmol) was slowly added to a stirred suspension of anhydrous potassium carbonate (1.17 g, 8.45 mmol) in acetone (40 mL), followed by the dropwise addition of dimethyl sulfate (0.8 mL, 8.45 mmol). The reaction mixture was stirred under heating conditions for 3 hours. After completion of the reaction, the inorganic salts were removed by filtration and the filter cake was washed with acetone. The filtrates were combined, dried and concentrated to afford methyl tetrahydropyran-4-carboxylate (1.1 g, 99% yield), which was used in the subsequent reaction without further purification. The product was analyzed by GC-MS showing m/z 145 (MH+); 1H NMR (300 MHz, CDCl3) δ 1.70-1.80 (m, 4H), 2.47-2.52 (m, 1H), 3.34-3.43 (m, 2H), 3.65 (s, 3H), 3.88-3.95 (m, 2H).
