B.
Aminomalononitrile p-toluenesulfonate.
Aluminum foil (13.7 g., 0.51 g. atom) is cut into half-inch squares and is covered with a
5% aqueous solution of mercuric chloride until a
mercury coating is visible on the
aluminum (
ca. 30 seconds). The
mercuric chloride solution is decanted, and the
amalgamated aluminum is washed twice with water, once with
ethanol, and twice with
tetrahydrofuran (Note
2). The amalgamated
aluminum is transferred to a
2-l. round-bottomed flask fitted with a
condenser, a stirrer, and a
250-ml. addition funnel and is covered immediately with
300 ml. of tetrahydrofuran (Note
2). The mixture is cooled in a dry ice-acetone bath, and the solution of
oximinomalononitrile from procedure A is added with stirring over a 15-minute period while the temperature is maintained at −15° to −30°. Stirring is continued for an additional 5 minutes. The dry-ice acetone bath is then removed, and the mixture is allowed to warm to room temperature. (
Caution! Cooling with a dry ice-acetone bath is usually needed to control the reaction.) After the spontaneous reaction subsides, the mixture is warmed to reflux until most of the
aluminum is consumed (45 minutes). The reaction mixture is cooled to room temperature,
200 ml. of ether is added with stirring, and the aluminum salts are removed by vacuum filtration through Celite filter aid. The solid is washed with
250 ml. of tetrahydrofuran (Note
2) followed by
500 ml. of ether (Note
3) and (Note
4). The original filtrate and washings are combined and concentrated to about 250 ml. by the use of a water aspirator and a bath at 40°. To the resulting brown solution is slowly added with stirring a mixture of
60 g. (0.32 mole) of p-toluenesulfonic acid monohydrate as a slurry in
250 ml. of ether (Note
5). The total volume is brought to 1 l. with
ether, the mixture is cooled to 0°, and the crystalline solid is collected by vacuum filtration. The product is washed successively with
200 ml. of ether,
200 ml. of cold (0°) acetonitrile, and
200 ml. of ether and dried at 25° (1 mm.) to give light tan crystals, m.p.
169–171° (dec.); yield,
75–79 g. (
78–82%).