Dimethylformamide → 2-Cyano-3-dimethylaminoacrolein

Participants

Reaction Steps

36 ml. (0.465 mole) Of N,N-dimethylformamide were stirred at 0° and 36 ml. (0.392 mole) of phosphorus oxychloride were added dropwise (a salt/ice bath was used in order to keep the reaction mixture at 0°). To the stirring semi-solid, faintly colored reaction mixture was added 300 ml. of 1,2-dichloroethane. Upon warming to room temperature by means of a water bath (25°), a clear solution resulted which was cooled to -7° with an ice/salt bath. A solution of 30 ml. (0.293 mole) of β-dimethylaminoacrylonitrile in 90 ml. of 1,2-dichloroethane was added dropwise keeping the temperature between -4° to -7°. The addition required about 1 hour. The cooling bath was removed and the clear amber reaction mixture allowed to come to room temperature. The reaction mixture was transferred to a 2 liter, round bottomed flask and the solvent removed in vacuo leaving a semi-solid orange colored residue. A 100 g. of ice was added to the residue which gradually dissolved with evolution of heat. The solution was transferred to a beaker and the pH adjusted to 8.4 by adding carefully 2N sodium hydroxide (815 ml. were required) to the stirred solution at 15°-20°. The resulting solution was extracted with ethyl acetate in a liquid-liquid extractor overnight. The ethyl acetate extract was cooled, the crystals which had separated were filtered off, washed with cold ethyl acetate and dried in vacuo, affording crude 2-cyano-3-dimethylaminoacrolein, as deep yellow prisms, m.p. 143°-144°. This material was dissolved in 500 ml. of hot water, treated with 2 g. of norite, the solvent removed in vacuo and the residue crystallized from absolute ethanol, producing the pure product in the form of light yellow prisms, m.p. 143°-144°.

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