Org. Synth. 1959, 39, 13
DOI: 10.15227/orgsyn.039.0013
DICYANOKETENE ETHYLENE ACETAL
[1,3-Dioxolane-Δ2,α-malononitrile]
Submitted by C. L. Dickinson and L. R. Melby
1.
Checked by James Cason, Edwin R. Harris, and William T. Miller.
1. Procedure
Caution! This preparation must be carried out in a good hood because hydrogen cyanide is evolved. It is inadvisable to allow contact of tetracyanoethylene with the skin.
Urea (4.0 g., 0.067 mole) is dissolved in
50 ml. of distilled ethylene glycol (Note 1) contained in a
125-ml. Erlenmeyer flask. Finely divided recrystallized
tetracyanoethylene (p. 877) (25.6 g., 0.20 mole) is added, and the flask is heated on a
steam bath at 70–75° with frequent stirring by hand with a
thermometer until solution is complete (about 15 minutes). The resultant brownish yellow solution is then cooled in ice water, and the precipitated
dicyanoketene ethylene acetal is collected on a
Büchner funnel. The acetal is first washed with two
25-ml. portions of cold ethylene glycol and then washed thoroughly with cold water to remove the
ethylene glycol. The
dicyanoketene ethylene acetal, which may be dried in air or in a
vacuum desiccator, is obtained in the form of large slightly pink needles, m.p.
115–116.5° (Note 2); yield
21–23 g. (
77–85%).
2. Notes
1.
Moisture in the
ethylene glycol leads to lowered yields. Satisfactory results are obtained with glycol collected at 199.5–201° from a simple distillation.
2.
The color may be removed by recrystallization from
ethanol after treatment with
decolorizing carbon; however, the melting point is not improved and occasionally is found to be lowered.
3. Discussion
The synthesis of
dicyanoketene ethylene acetal described here is a slight modification of one published recently.
2 The procedure has been applied successfully to the synthesis of
dicyanoketene dimethyl acetal and
dicyanoketene diethyl acetal.
2Dicyanoketene ethylene acetal reacts with tertiary amines to give quaternary ammonium inner salts.
2 Similarly, it reacts with sulfides to give sulfonium inner salts.
2 These products are generally solids that can be used to characterize tertiary amines and sulfides. Dicyanoketene acetals can be converted to pyrimidines, pyrazoles, or isoxazoles in one step.
3
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
1,3-Dioxolane-Δ2,α-malononitrile
ethanol (64-17-5)
hydrogen cyanide (74-90-8)
decolorizing carbon (7782-42-5)
ethylene glycol (107-21-1)
urea (57-13-6)
Dicyanoketene ethylene acetal (5694-65-5)
dicyanoketene dimethyl acetal
dicyanoketene diethyl acetal
Tetracyanoethylene (670-54-2)
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