Water → 3-Trifluoroacetyl-3-cyanopropionaldehyde diethyl acetal

To a 40°-45° C. stirring suspension of hexane-washed sodium hydride (5.5 g of a 60% dispersion, 0.14 mol) in 200 mL of dried tetrahydrofuran is added dropwise a solution of ethyl trifluoroacetate (15 g, 0.11 mol) and 3-cyanopropionaldehyde diethyl acetal (17 g, 0.11 mol) in 100 mL of dry tetrahydrofuran. The previously gray suspension slowly turns light brown in color. The reaction mixture is stirred at 50°-55° C. overnight before being quenched by slow addition of 2-propanol (15 mL). Rotary evaporation of the volatiles yields a dark oil, to which is added 150 mL of pH 7 water. Unreacted starting materials are conveniently removed by washing the aqueous layer with diethyl ether (3×30 mL). The basic aqueous phase is then acidified with 12N hydrochloric acid and extracted with ethyl acetate (2×100 mL). The combined organic layers are washed once with saturated sodium bicarbonate (40 mL) and once with brine (15 mL) before being dried over magnesium sulfate. Rotary evaporation yields a reddish oil which is flash chromatographed over silica gel using 4:1 hexane-ethyl acetate as eluent to provide the desired product (9 g, 32%) as a yellow oil.