Ammonium Chloride → Ethyl 2-methylidenebutanoate

To CuCN (26.9 g, dried in advance under vacuum) was added under nitrogen atmosphere about 500 ml of dry tetrahydrofuran. The mixture was kept at −78□, and 100 ml of methyl magnesium bromide (3.0M diethylether solution) was slowly added thereto under mechanical stirring. The thick mixture was stirred for about 30 minutes at −78□. Ethyl 2-bromomethylacrylate (28.9 g, 150 mmol, Synthetic method: Villieras, J. and Rambaud, M. Synthesis, 1982, 914) dissolved in about 30 ml of dry tetrahydrofuran was slowly added thereto. The temperature of the reaction mixture was slowly raised to room temperature over two hours. The reaction was completed by slowly adding saturated ammonium chloride solution (˜50 ml). The reaction mixture was filtered through Celite to remove the precipitates, and then washed with diethylether. The organic layer was washed with water and saturated sodium bicarbonate solution (300 ml×2), dried (anhydrous Na2SO4), and concentrated under reduced pressure to give 26.7 g (stoichiometric yield) of a transparent liquid. This liquid was identified by 1H-NMR (500 MHz, CDCl3) and was confirmed to be the title compound having about 75% of w/w purity.