synthesis of dimethyl 2-fluoromalonate: Dimethyl malonate (19.8 g, 0.15 mol) and Cu(NO3)2·2.5H2O (3.50 g, 15 mmol) were dissolved in acetonitrile (85 mL), the mixture was cooled to 0–5 °C and stirred at 650 rpm using an overhead stirrer. After purging the system with N2 for 5 minutes, fluorine gas (20% v/v in N2, 50 mL min-1 , 170 mmol) was introduced into the reaction mixture for 7 h. After purging with nitrogen for 20 minutes, the solvent was removed in vacuo and the residue was partitioned between water (30 mL) and ethyl acetate (20 mL). The aqueous phase was extracted with ethyl acetate (2 × 20 mL) and the combined organic layer was washed with saturated brine (20 mL). After drying over sodium sulphate, the solvent was evaporated under reduced pressure to give dimethyl 2-fluoromalonate (21.8 g, 97% yield, 95% purity) as a colourless oil;
IR (neat, cm-1 ) 2962, 1748, 1438, 1250, 1206, 1112, 1016; δH (CDCl3, 400 MHz) 3.85 (6H, s, CH3), 5.31 (1H, d, 2 JHF 48.0, CHF); δF (CDCl3, 376 MHz): -195.73 (d, 2 JHF 48.0, CH–F); δC (CDCl3, 100 MHz) 53.48 (CH3), 85.19 (d, 1 JCF 197.2, C–F), 164.39 (d, 2 JCF 24.0, CvO); m/z (EI+ ) 150 (3%, [M]+ ), 119 (42%, [M-OMe]+ ), 91 (73%, [M-COOMe]+ ), 59 (100%, [COOMe]+ ).
