A
2-l., four-necked flask equipped with a
stirrer,
thermometer,
dropping funnel, and
reflux condenser is charged with
296 g. (2.00 moles) of cinnamic acid and
600 ml. of dichloromethane. The mixture is heated to reflux and a solution of
290 g. (2.05 moles) of chlorosulfonyl isocyanate (Note
1) in
100 ml. of dichloromethane is added dropwise, with stirring, over a period of 45 minutes. After a few minutes the solution becomes clear and, after about one-half of the
isocyanate has been added, the carboxylic acid amide
N-sulfonyl chloride begins to precipitate. At the end of the addition, the reaction mixture is heated for an hour to complete the evolution of
carbon dioxide (Note
2).
N,N-Dimethylformamide (300 g., 4.11 moles) (Note
3) is added, with stirring, over a 15-minute period, while cooling with ice to an internal temperature of 15–20°. The reaction mixture is stirred for an additional 15 minutes and then poured onto
ca. 800 g. of ice. After the ice has melted, the resulting layers are separated and the aqueous phase is extracted once with
100 ml. of dichloromethane. The organic phases are combined and extracted six times with 100-ml. portions of water to remove most of the
N,N-dimethylformamide (Note
4). The resulting organic solution is dried for 2 hours with
50 g. of potassium carbonate, decanted from the drying agent, and concentrated by distillation at atmospheric pressure. The resulting oil is distilled through a
10-cm. Vigreux column (Note
5) to give
197–225 g. (
78–87%) of
cinnamonitrile, b.p.
92–94° (1 mm.),
n25D 1.5998 (Note
6). Its
1H NMR spectrum (60 MHz., CCl
4, 36°) δ, (multiplicity, coupling constant
J in Hz., number of protons): 5.79 (d,
J = 17, 1H), 7.29 (d,
J = 17, 1H), 7.35 (s, 5H).