[Synthesis]
Under nitrogen protection, 5.34 g (21.00 mmol) LiAlH(t-BuO)3 was dissolved in 40 cm3 anhydrous THF and added dropwise to a solution of 1.68 g (15.00 mmol) citraconic anhydride dissolved in 50 cm3 anhydrous THF over a period of 30 min, and the reaction temperature was maintained at -30 °C. After the dropwise addition was completed, the temperature of the reaction system was raised to -15°C and maintained for 3 hours. Subsequently, the reaction mixture was slowly warmed up to room temperature. Upon completion of the reaction, the reaction was quenched with 50 cm3 1M HCl solution, followed by washing with saturated NaCl solution and extraction of the crude product with EtOAc (3 x 50 cm3). The organic phases were combined and dried with MgSO? The solvent was removed by concentration under reduced pressure to give the crude product. Purification by silica gel column chromatography (eluent: petroleum ether/ethyl acetate=80:20) afforded 5-hydroxy-3-methylfuran-2(5H)-one (7a, 1.023 g, 60% yield) and 4-methyl-5-hydroxyfuran-2-one (7b, 116 mg, 7% yield) as yellow oils, respectively.TLC analysis (unfolding agent: petroleum ether/ethyl acetate= 80:20) showed that the Rf values of 7a and 7b were 0.16 and 0.15, respectively. 1H NMR (400 MHz, acetone-d6) δ of 7a: 6.67 (bs, 1H), 6.02 (bs, 1H), 5.87 (p, J = 1.5 Hz, 1H), 2.08 (d, J = 1.5 Hz, 3H) ppm; 13C NMR (100 MHz, acetone-d6) ppm. MHz, acetone-d6) δ: 171.30 (C), 166.65 (C), 118.68 (CH), 100.25 (CH), 13.15 (CH3) ppm; MS (EI): m/z (%) = 114.0 ([M]+, 2), 113.0 (7), 86.0 (61), 85.0 (13), 69.0 ( 100), 68.0 (82), 41.1 (50), 40.1 (65), 39.1 (93). |