In a test tube fitted with a stir bar, N-fluorobis(methylsulfonyl)imide (38.2 mg, 0.2 mmol) and 1,2-dichloroethane (1.0 mL) were added and stirred at room temperature until completely dissolved. Subsequently, diethyl 2-methylmalonate (17.4 mg, 0.1 mmol) and tetraisopropoxy prototitanate (0.016 mL, 0.05 mmol) were added to this solution and the reaction was carried out for 12 hours at room temperature. After completion of the reaction, water was added, extracted with dichloromethane (3 times), the organic layers were combined, washed with saturated brine, dried over anhydrous sodium sulfate, filtered and concentrated to give the crude product. The crude product was analyzed by 19F-NMR and the yield of the target product diethyl 2-fluoro-2-methylmalonate was quantified using hexafluorobenzene as an internal standard. Finally, the product was purified by silica gel column chromatography (eluent: ethyl acetate/hexane = 10/90, v/v) to afford the purified diethyl 2-fluoro-2-methylmalonate (7) as a colorless and transparent liquid (18.7 mg, 0.097 mmol, 97% yield).
