General procedure for the synthesis of ethyl tetrahydrofuran-2-carboxylate from 2-tetrahydrofurancarboxylic acid: to a solution of 2-tetrahydrofurancarboxylic acid (20 g, 172.2356 mmol) in anhydrous ethanol (100 mL) was slowly added concentrated sulfuric acid (0.46 mL) as a catalyst. The reaction mixture was placed under reflux conditions and stirred for 16 hours. Upon completion of the reaction, the mixture was cooled to room temperature. Subsequently, the reaction mixture was diluted by adding water (100 mL) and extracted with ether (3 x 100 mL). The organic phases were combined and washed sequentially with saturated aqueous sodium bicarbonate solution (2 x 50 mL) and saturated aqueous sodium chloride solution (100 mL). The organic layer was dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to afford ethyl tetrahydrofuran-2-carboxylate (22.5964 g, 91% yield) as a colorless liquid. The product was detected by LRMS at m/z 145 (M + H)+. 1H NMR (CDCl3, 300 MHz) data were as follows: δ 4.38 (1H, dd, J = 4.9, 8.1 Hz), 4.14 (2H, q, J = 7.2 Hz), 3.99-3.92 (1H, m), 3.88-3.81 (1H, m), 2.24- 2.12 (1H, m), 2.00-1.79 (3H, m), 1.22 (3H, t, J = 7.2 Hz).
