1-(4-methoxyphenyl)propane-1,2-dione

121-97-1

10557-27-4

A two-necked round-bottomed flask was placed in a 0°C ice bath under nitrogen protection and sodium nitrite (4.14 g, 60.0 mmol) was added to a stirred solution of p-methoxypropiophenone (1.64 g, 10.0 mmol) in ether (10 mL). Subsequently, 37% aqueous hydrochloric acid (9.86 g, 0.1 mol) was added slowly and dropwise. The reaction mixture was stirred continuously at room temperature for 24 hours. Upon completion of the reaction, it was washed with saturated aqueous sodium bicarbonate solution to neutral and the organic layer was extracted with ethyl acetate (3 x 10 mL). The organic layers were combined, dried with anhydrous sodium sulfate and concentrated under reduced pressure to remove the solvent. The crude product was purified by silica gel column chromatography (silica gel dosage was 20 g/g of crude product, eluent was petroleum ether/ethyl acetate, 85:15) to afford 1-(4-methoxyphenyl)propane-1,2-dione (0.77 g, 43% yield) as a yellow solid. The thin-layer chromatographic Rf value was 0.36 (petroleum ether/ethyl acetate, 8:2); the melting point was 50-51°C (literature values: 44-45°C and 38-39°C). Infrared spectroscopy (thin-film method) showed absorption peaks located at 2935, 1708, 1655, 1597, 1571, 1509, 1422, 1307, 1261, 1152, 1025, 900, 841, 755, and 693 cm^-1. NMR hydrogen spectra (300 MHz, CDCl3) δ values: 2.50 (s, 3H, CH3CO ), 3.88 (s, 3H, CH3OAr), 6.88-7.02 (m, 2H, H-3'), 7.96-8.05 (m, 2H, H-2'). NMR carbon spectrum (75 MHz, CDCl3) δ values: 26.4 (CH3CO), 55.5 (CH3OAr), 114.0 (C-3'), 124.5 (C-1'), 132.6 (C-2'), 164.7 (C-4'), 189.9 (CH3COCO), 201.1 (CH3COCO). Calculated elemental analysis (C10H10O3): C, 67.41; H, 5.66. Measured values: C, 67.43; H, 5.65.