Methanol → Methyl oxolane-3-carboxylate

To a solution of tetrahydro-3-furancarboxylic acid (10.00 g, 86.0 mmol) in MeOH (172 mL) was added sulfuric acid (13.8 mL, 258 mmol). The reaction was heated to reflux for 18 h. The reaction was then cooled to rt and concentrated. The residue was partitioned between water (500 mL) and DCM (200 mL). The phases were separated and the aqueous fraction was extracted with DCM (200 mL). The combined organic fractions were washed with saturated aqueous NaHCO3 (200 mL) and brine (200 mL), dried over Na2SO4, filtered, and concentrated to afford methyl tetrahydro-3-furancarboxylate (10.1 g, 78 mmol, 90% yield) as a pale yellow oil. 1H NMR (400 MHz, CDCl3) δ ppm 3.99 (t, J=8.4 Hz, 1H), 3.86-3.95 (m, 2H), 3.76-3.86 (m, 1H), 3.71 (s, 3H), 3.01-3.18 (m, 1H), 2.03-2.32 (m, 2H).