Organic Syntheses, CV 5, 204
[Isocyanic acid, anhydride with chloroacetic acid]
Submitted by A. John Speziale and Lowell R. Smith
1.
Checked by Leif A. Hoffmann and V. Boekelheide.
1. Procedure
In a
250-ml. round-bottomed flask fitted with a
magnetic stirrer (Note
1), a
thermometer, and a
condenser carrying a calcium chloride tube (Note
2) are placed
46.7 g. (0.5 mole) of α-chloroacetamide (Note
3) and
100 ml. of ethylene dichloride. The mixture is chilled in an
ice bath to about 2° and stirred while
76.2 g. (0.6 mole) of oxalyl chloride (Note
4) is added all at once. The mixture is removed from the ice bath, stirred for 1 hour, and then heated to reflux at 83° with stirring for 5 hours (Note
5). The solution is chilled in an ice bath to 0–10°, the condenser is replaced by a
120-mm. distillation column packed with glass helices, and the solvent is removed at 70 mm. pressure with stirring. The ice bath is removed after the solvent boils without foaming and is replaced by a
heating mantle or oil bath. Distillation gives
39 g. (
65%) of
α-chloroacetyl isocyanate, b.p.
68–70° (70 mm.), as a colorless oil,
n25D 1.4565.
2. Notes
1. For larger-scale preparations mechanical stirring is recommended.
2. Moisture must be rigorously excluded from the reaction mixture and the product.
3. The
α-chloroacetamide was obtained from Eastman Kodak Co. and used without purification.
4. The
oxalyl chloride was obtained from Aldrich Chemical Co. and used without purification.
Oxalyl chloride vapor is irritating and toxic, and therefore manipulations must be carried out in a
hood.
5. Because a large amount of
hydrogen chloride is evolved, the reaction must be carried out in a hood.
3. Discussion
4. Merits of the Preparation
The procedure may be adapted for the preparation of other acyl isocyanates (
i.e.,
dichloroacetyl,
trichloroacetyl,
phenylacetyl,
diphenylacetyl,
benzoyl, etc.) and is generally more convenient than the reaction of acid chlorides with
silver cyanate.
3 4 Acyl isocyanates react with amines, alcohols, and mercaptans to yield acyl ureas, carbamates, and thiocarbamates, and have been show to undergo a variety of interesting reactions.
5
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