Org. Synth. 1950, 30, 43
DOI: 10.15227/orgsyn.030.0043
ETHYL PHENYLCYANOACETATE
[Acetic acid, cyanophenyl-, ethyl ester]
Submitted by E. C. Horning and A. F. Finelli
1.
Checked by William S. Johnson and H. Wynberg.
1. Procedure
Sodium ethoxide is prepared from 12.0 g. (0.52 g. atom) of sodium and 300 ml. of anhydrous ethanol in a 1-l. three-necked round-bottomed flask fitted with a reflux condenser carrying a calcium chloride tube. After the sodium has dissolved completely, the condenser is arranged for distillation under reduced pressure and the excess ethanol is removed by heating the flask on a steam bath while the system is maintained at the pressure obtained with an ordinary aspirator (Note 1).
As rapidly as possible, after removal of the ethanol, the flask is fitted with a rubber-sealed stirrer, a dropping funnel, a distilling head containing a thermometer, and a condenser arranged for distillation into a flask protected by a calcium chloride tube. There are then added 300 ml. (292 g., 2.5 moles) of dry diethyl carbonate, 80 ml. of dry toluene, and 58.5 g. (0.50 mole) of phenylacetonitrile (Note 2). The flask is heated, with good stirring, and the cake of sodium ethoxide soon dissolves. When distillation has started, dry toluene is added dropwise at about the same rate that the distillate is collected. Approximately 200–250 ml. of toluene should be added in a period of 2 hours (Note 3) while stirring and distillation are continued.
The mixture is cooled and transferred to a 1-l. beaker. After addition of 300 ml. of cold water, the aqueous phase is acidified with 35–40 ml. of acetic acid. The layers are separated and the water solution is extracted with three 75-ml. portions of ether. The organic solutions are combined, washed with 100 ml. of water, and dried over anhydrous magnesium sulfate. The low-boiling solvents are removed by distillation at atmospheric pressure, and the residue is distilled under reduced pressure through a short (15-cm.) Vigreux column. After a 1–5 g. forerun, the product is collected at 125–135°/3–5 mm. (Note 4). The yield is 66–74 g. (70–78%).
2. Notes
1.
The success of this procedure is dependent upon the quality of the
sodium ethoxide. The
ethanol should be dried before use,
2 and the
sodium ethoxide should not be heated to a temperature higher than 90–100°. The dry material can be transferred, but in this case it is advisable to prepare it in the flask in which it is to be used.
2.
Commercial
phenylacetonitrile should be distilled before use. The
diethyl carbonate and
toluene are dried by distillation.
3.
Any
ethanol remaining in the
sodium ethoxide, together with the
ethanol produced during the reaction, is removed during this period. The progress of the carbethoxylation reaction can be followed by temperature readings. During the first half of the heating period distillation usually occurs at a vapor temperature of 80–85°, but as the reaction nears completion and the
ethanol is removed, the temperature rises to 110–115°. Near the end of the period, the
sodium salt of ethyl phenylcyanoacetate appears as a precipitate.
4.
Other observed boiling points are
129–131°/3 mm.,
145–150°/7–8 mm. The product is a colorless liquid,
nD25 1.5012-1.5019.
3. Discussion
This procedure is a modification of the method of Wallingford, Jones, and Homeyer.
3 The carbethoxylation of
phenylacetonitrile is the only method of preparative value for this compound.
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
sodium salt of ethyl phenylcyanoacetate
ethanol (64-17-5)
acetic acid (64-19-7)
ether (60-29-7)
toluene (108-88-3)
sodium (13966-32-0)
sodium ethoxide (141-52-6)
phenylacetonitrile (140-29-4)
magnesium sulfate (7487-88-9)
diethyl carbonate (105-58-8)
Ethyl phenylcyanoacetate,
Acetic acid, cyanophenyl-, ethyl ester (4553-07-5)
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