Example 1; Preparation of 4-bromo-5-ethoxy-5H-furan-2-one [0128]; The procedure may be followed as described by C. Escobar et al. (Ann. Chem. Soc., Vol. 24, No. 2, pp. 1998, Quim., 1971, 67, 43-57). A solution of bromine (4.05 mL, 78.2 mmol) in carbon tetrachloride (25 mL) was added dropwise to a solution of 5-ethoxy-5H-furan-2-one (II, R1 = Et) (10.0 g, 78.0 mmol) in carbon tetrachloride (50 mL) at 0 °C over a period of 0.5 h. The reaction was carried out by stirring the reaction mixture at 0 °C for 1 min. The reaction mixture was stirred at 0 °C for 1 h, followed by continued stirring for 2 h at room temperature. The solvent was evaporated under reduced pressure and the residue was purified by short distillation (~0.5 mmHg). The 100 °C-120 °C fractions were collected to afford 4-bromo-5-ethoxy-5H-furan-2-one (13.2 g, 82% yield) as a yellow oil.1H-NMR (500 MHz, CDCl3) δ 6.24 (s, 1H), 5.63 (s, 1H), 3.71 (m, 1H), 3.63 (m, 1H), 1.14 (t, J = 7.1 Hz, 3H) ppm.
