Diethyl (cyanomethyl)phosphonate → HCID 67451464, compound

To a solution of diethyl cyanomethylphosphonate (4.09 g; 23.1 mmol) in dry THF (200 mL) at 0° C. under nitrogen was added potassium t-butoxide (23.1 mmol; 1M solution in THF). The mixture was stirred for 1 hour. The solution of 2,2-difluorocyclopropanecarbaldehyde from Step A was added and the mixture was stirred while allowing to warm to ambient temperature. A portion of the solvent was removed under reduced pressure and the remaining solution was diluted with ammonium chloride solution (50 mL). The mixture was extracted into ethyl acetate (2×50 mL). The combined extracts were dried (magnesium sulfate and sodium sulfate), filtered and evaporated under reduced pressure. The material was purified by chromatography on silica gel, eluting with hexane/ethyl acetate (3:1) to give 3-(2,2-difluorocyclopropyl)acrylonitrile (0.50 g) as a pale yellow oil (containing some ethyl acetate).