Formaldehyde → 2-(Piperidin-1-ylmethyl)prop-2-enenitrile

Cyanoacetic acid (51 g., 6 mole) was dissolved in 150 ml. of dioxane, the solution cooled to 5° C. and piperidine (53 g., 0.6 mole) dripped in while maintaining the temperature at 10°-15° C. Then, 37% aqueous formaldehyde (109.5 g., 1.35 mole) was slowly added at 0°-10° C. After two hours, the ice bath was removed and the mixture stirred overnight at 20°-25° C. It was then stripped at 15 mm. pressure and bath temperature of 48° C. The residue was chilled, mixed with 100 ml. of ether, saturated with sodium chloride and the ether layer separated. This extract was washed with two 25 ml. portions of cold 5% aqueous potassium carbonate and finally with 10 ml. of ice water. The ether solution was dried over anhydrous magnesium sulfate, filtered, stripped and fractionated using a Vigreux column. The fraction boiling at 86°-88° C./2 mm. was of practically analytical quality, 40.8 g., Rf 0.66 on silica gel using chloroform-methyl alcohol (90:10) development. This is, however, a known compound.