To a pre-cooled (0 °C) solution of crude ester 4s (ca. 1.00 mmol) in MeOH -H2O mixture (4 mL, 1:1 v/v), solid K2CO3 (0.415 g, 3.00 mmol) was added in one portion. After stirring for 3 h, the solvents were evaporated under reduced pressure to dryness, the resulting solid residue was suspended in EtOH (10 mL), and the mixture was filtered. The filtrate was concentrated under reduced pressure, the residue was triturated with CH2Cl2 (10 mL) and filtered to give pure product 4s after drying on air. Yield 87.4 mg, 0.31 mmol, 31% over 3 steps. Yellowish solid, mp > 200 °C (dec.). 2,2-Difluoro-4-methylpent-3-enamide (6). Solution of ester 4b (1.00 g, 5.62 mmol) in EtOH (10 mL) was cooled to 0 °C in ice/water bath. Gaseous ammonia was bubbled through the solution for 1 h at a constant rate (ca. 10 mL/min). Upon completion of the reaction (concluded by 1 H NMR spectrum of s small aliquot of the reaction mixture) the organic solvent was evaporated under reduced pressure, crude residue was triturated with hexanes (20 mL), filtered and dried on air to give pure amide 6.